WB8NBS

NBS
This Blog will document projects I have
in progress or completed. You can search for my
handle on Flickr, Facebook, YouTube, or Picasa
for photos. I will link some of those here.

Rust Removal Using Electrolysis

Why would you do this?

If you are a person who only buys new stuff at the big orange store you probably won’t need to remove rust. Myself, I am retired and have more time than money.  In other words, “Cheapskate”. I watch for garage and estate sales with old tools I can use. My garage is full of restored tools, most tuned to be as good or better than when they were new. “They don’t make them like they used to” is certainly true for woodworking hand tools.

This is my current favorite hand plane. Found at a flea market, all exposed surfaces had a good coat of rust and to further insult, someone had varnished over the rust. It now works beautifully.

Stanley 5 1/4 Derusted and tuned

Stanley 5 1/4 Derusted and Tuned

Rust removal is not limited to tools. There is an active Facebook group for people using electrolysis in large tanks to clean flea market cast iron cookware. Old car parts need it. I even saw someone had de-rusted a whole car. Near my home there used to be a restaurant “Key Wester”, in the lobby there was a Spanish cannon retrieved from the waters off Florida that had been cleaned with electrolysis. The sign said it was in the tank for months.

There are degrees of rust. I avoid tools with areas that look like scabs. Those will clean (with difficulty) but leave a pit in the surface that may or may not affect the function of the tool. An even layer of surface rust, even if heavy, will usually clean off to a usable surface.

Electrolysis won’t damage underlying iron but doesn’t actually remove the rust. It just changes the red oxide to a black form that is easily scrubbed off, so there’s still elbow work involved. Electrolysis in itself won’t remove paint or plating. But if the paint is loose, it may come off in the scrubbing. I have not had a problem with the Japanning used on hand planes coming off, though any coating that is rusted underneath may separate regardless of the cleaning method used.

Components

These are the things you need to get started.

A waterproof container large enough to submerge the subject. Best to use plastic. A metal container will possibly trigger a short circuit though I have seen people using steel tubs with good results. I usually use either a six gallon bucket or a three gallon bucket. Some of the cast iron cookware people use barrels.

Small Tank in Action

Small Tank in Action

 

Objects that won’t fit in a bucket can be handled by making a tank to suit. I have de-rusted several full size hand saw blades in a homemade tray consisting of a plywood bottom and scrap molding for the sides. I lined the tray with plastic sheeting and laid electrodes flat in the bottom.

Saw Cleaning Tray From Scraps

Saw Cleaning Tray From Scraps

A flat tray like this will only do one side of the iron. You have to turn it over every half hour or so. Also I found the plastic grid insulators left a pattern on the saw blade. To reduce that, just move the blade a bit every 15 minutes.

Hand Saw Blade Under Electrolysis

Hand Saw Blade Under Electrolysis

De-rusting and scrubbing can be a dirty mess so it’s best to do it outside the house. I usually move to the driveway and do scrubbing on an old plastic sign. It’s a good use for those placards left up after election day.

 

An anode (or anodes) at the inside edge of the tank. Anodes are connected to the positive terminal of the power supply. Steel plates are good, I have seen cut up coffee cans, discarded hacksaw blades, even rebar.  Remove paint or other coating facing the inside of the tank or they won’t work. Some people warn against using stainless steel because of possible heavy metal contamination of the electrolyte. However the cookware people on Facebook recommend ONLY using stainless, and I use stainless plate salvaged from electronic equipment, bent to clip over the sides of the buckets.

Avoid aluminum and galvanized steel. Aluminum will disappear and Zinc contaminates the electrolyte.

It’s a good idea to add a layer of porous electrical insulation. Too often one of the objects falls into the tank and can short circuit the power supply.  I use plastic grid cut from a milk crate over my larger anodes. Occasionally the plates need to be cleaned, so make any insulation removable. Multiple anode electrodes must be electrically bonded together.

Small Electrodes, Large Electrodes

Small Electrodes, Large Electrodes

 

A source of Direct Current. This can be from 3 to 24 volts, an automotive battery charger is typically used. A small one with 6-15 amp capacity is fine, lots of these show up at garage sales. Try to get one with a meter so you can see if you are drawing too much or too little current, and bonus points if the charger has a six volt setting. Switching down from 12 to 6 volts is an easy way to bring the current into range if you mix the electrolyte too strong.

Battery Chargers

Battery Chargers

Some newer chargers have short circuit protection built in and will not start if they don’t see at least some voltage on the leads. The charger above on the right has an “Activate” position that will source current no matter what into a dead battery. Also watch out for really old chargers that have Selenium rectifiers. They work but are inefficient and if you short one long enough to blow out the rectifier you can’t believe how bad it smells. DAMHIKT.

There are people using cast off PC power supplies for electrolysis but that’s way beyond the scope of this article.

 

Electrolyte to make the solution electrically conductive. The classic electrolyte is Arm and Hammer Washing Soda (Sodium Carbonate) dissolved in plain water. Many supermarkets carry it. Baking soda (Sodium Bicarbonate) works but is more expensive. People also use Borax but I have not tried it. All these are non-toxic, you can pour it down the drain or on the lawn when you’re finished.

Sodium Carbonate

Sodium Carbonate

The starting recipe is one tablespoon per gallon of water. That’s about a handful in five gallons. Washing Soda doesn’t dissolve easily in cold water, if you heat the first gallon it will dissolve better. I fill the tank half way then pour in water heated in an old coffee pot. Stir until the Carbonate dissolves then fill the tank the rest of the way.  Undissolved powder left in the bottom of the tank will eventually go into solution because the mixture warms from the heating effect of the current which gradually increases the power draw, possibly overloading the charger long after you’ve started it up.

 

Scrubbing tools. Again, electrolysis doesn’t remove the rust, it changes it to a form that is easily scrubbed off.  Most chemical de-rusting methods are the same in this regard. My favorite scrubbing tool is a brass bristled brush. Stiff enough to remove black oxide but not so stiff that it scratches cast iron. Brass won’t round over edges that shouldn’t be rounded over, like the mouth of a plane. Rotary steel wire brushes will do that. Brass brushes used to be common in the barbecue section of  hardware stores, but I only see steel these days. Another source is suede brushes from a shoe repair shop.

Stiff plastic brushes may also work, and Scotch Brite scrubbing pads are used often.

Scrubbing Station

Scrubbing Station

Keep a bucket of clean water next to the scrubbing area. When a piece of iron is scrubbed clean it will flash rust again very quickly in the air. The easiest way to avoid re-rusting is to store the cleaned parts submerged in fresh water. That may be counter intuitive but it keeps oxygen away from the metal until you are ready to dry the piece.

Scrubbing with a brass brush when the part is still wet with carbonate solution will transfer a small amount of brass to the surface of the iron giving the part a goldish cast. I like it, I think it looks antiquey. If you don’t want color, just rinse the part good in clean water before scrubbing. I scrubbed the saw plate in the above picture with a copper brillo pad and, surprise, the saw has a copper tint now.

 

Set up the electrolysis tank. So far we have a bucket full of Carbonate solution with anode electrodes around the inside surface. The iron components to be de-rusted must be carefully hung in the middle of that solution so they don’t touch the anodes. I use a board with fat copper wire threaded through numerous holes, this forms the cathode and is connected to the negative terminal of the charger. The board has screws near the ends spaced so it can be wedged onto the sides of the bucket, providing some security against parts accidentally moving and causing a short circuit. Battery clips soldered to the Copper buss support smaller items while larger parts like a plane body get dangled from their own wire wrapped around the cathode buss. A large part may be drawing several amps so you need at least #18 wire. Remember, positive to the outside anodes, negative to the tool.

Cathode Hangers, Large Tank & Small Tank

Cathode Hangers, Large Tank & Small Tank

Another caveat, the process is essentially line of sight from the anode to the part. If you have one part shadowed by another part, it won’t get cleaned well, so you have to arrange dangling objects carefully.

Once the parts are in the tank make one last visual check for potential short circuits. You won’t be able to see through the soup when the process is running. If you’re sure every thing is separated, start the charger and read the current. A good initial amount would be 2/3 rated current as it will increase a bit as the solution warms up. If the current is not high enough, add more carbonate. You can just stir some in, but a better way is to make a hot, concentrated solution in the coffee pot then pour some of that into the tank. If the current is too high you can either lower the voltage or add water to the tank to dilute the carbonate.

Six Gallon Tank

Six Gallon Tank

 

Small Tank in Action

Small Tank in Action

It will take from one to six hours in the tank to get most parts back to an clean state. I usually remove parts every hour and scrub them a bit just to see how the reaction is going. Unlike some chemical methods, it doesn’t hurt to leave the parts in longer than necessary.

After the final scrubbing, one at a time pull the parts out of the rinse pail and thoroughly dry them with towels, heat, and compressed air if there are any holes. Apply oil or paste wax to the bare iron to inhibit future rusting.

 

Other ways to de-rust an iron object. 

Search “electrolysis rust removal” on Google or YouTube. Many chemical methods use a mild acid. Vinegar is popular, it’s usually 6% acetic acid and sometimes salt is added. Naval Jelly works quickly, it contains phosphoric acid. Christopher Schwarz mixes up a citric acid solution, you can get citric acid powder from Amazon. Acid techniques will eat away the underlying metal if the part is left in the soup too long. Electrolysis uses a basic solution which is more iron friendly.

Evapo-Rust is the chemical mentioned most often. Nobody knows what’s in it, the MSDS says “Proprietary non-hazardous chelating agent”. It  supposedly will not attack bare iron if you leave it too long.

Mechanical methods remove rust quickly but run the risk of also removing or scratching the iron. Years ago I restored my very rusted garage sale table saw with Wet/Dry sandpaper lubricated with WD40. Scraping the rust with a razor blade is not perfect but is good for something like an old saw where you want to keep the etch intact. A rotary wire brush in a grinder works quickly but will erode a cast iron part. If you don’t care about flat surfaces and crisp edges go for it.

 

This is an estate sale plane I’m using as a before/after electrolysis demonstrator. The parts were laid on their side in a shallow pan half submerged with a sheet anode in the bottom. I masked the still rusty side with duct tape before scrubbing.

I thought the plane was a generic piece of crap when I bought it but after revealing the Zenith logo stamp and some research, I find it is a very nice tool – Sargent OEMed to Marshall Wells Hardware Co. It’s identical to a Sargent 14C which was only made from 1910 to 1918 and well worth restoring.

Zenith Electrolysis Example

Zenith Electrolysis Example

Zenith Cleaned Side

Zenith Cleaned Side

 

Zenith Before and After Bottom

Zenith Before and After Bottom

Method for Sharpening Hollow Plane Blades

I recently acquired two wooden beading planes, a 1/4 inch and a 1/2 inch. A beaded edge on a wooden project is decorative and more resistant to damage than a plain square edge. Planes that do beading are not particularly rare, this one came from the MWTCA tool show at Garfield Farm August 4, 2019.

Quarter Inch Beading Plane

Quarter Inch Beading Plane

This is what a beading plane does. The bottom beads are single, the top two have been cut in from each of the two sides. The small notch that forms the inside of the round is called the quirk.

Quarter Inch Beads Cut

Quarter Inch Beads Cut

A Stanley 45 came with seven beading cutters, 1/8″ to 1/2″. Because of the design of the skates, a Stanley 45 bead has a fat quirk. Wooden bead planes make a more desirable, delicate profile. Here are the blades from my two beading planes. See how the profile lines up with the bottom right or the top left bead in the above picture. The small flat part on the left edge cuts the quirk and it, plus the concave part, must match the profile of the plane’s bed precisely. The quirk is extra important because it is the first thing that touches the wood and guides the plane through the rest of the cut. Thus it receives heavy wear and most beading planes have hard boxwood reinforcement there.

Half Inch and Quarter Inch Beading Cutters

Half Inch and Quarter Inch Beading Cutters

Shaping the Cutter

The half inch beading plane had a seriously abused cutter. The quirk part had been improperly sharpened so the first order of business was to grind that back to a proper square edge on the bench grinder. Inserting the cutter back in the plane with the quirk edge aligned showed the concave part was now about an eighth of an inch too high.

Shaping the concave edge was done by scribing the bed profile on the back of the blade, then using a rotary die grinder. I have also used a Dremel tool on Stanley 45 cutters with a similar process. It’s important the tools not move, so the grinder was secured in a jig I made years ago for a different purpose.

Grinder Support Jig

Grinder Support Jig

Some fussing with shims was required before the grinding point was parallel to the workbench.

Checking that Grinding Point is Parallel to Workbench

Checking that Grinding Point is Parallel to Workbench

Now that the grinder is true to the bench, I can make a 30 degree block to hold the cutter at the right bevel angle. This 30-60-90 block was made with dozens of cutoff corners from making hexagonal box lids. I used to use it as a bicycle wheel chock. It just needed a 3/8″ spacer to bring the ramp up to the grinding point. The small bit of cherry under the left edge registers against my workbench to hold the block true.

Note that not all cutters are made to 30 degrees. Stanley 45 beaders are 35 degrees and you have to make a ramp to match that or you will spend a long time grinding.

Thirty Degree Cutter Support Block

Thirty Degree Cutter Support Block

A photo of the ramp from the top.  Black stains are from grinding swarf. The pine spacer has been planed off to match the ramp surface.

Thirty Degree Cutter Support Block

Thirty Degree Cutter Support Block

All the pieces are together and I could reshape the concave part of the half inch cutter. I noted cheap grinding points are not straight or very round so spent some time with a diamond grinding wheel dresser to clean it up. It took about an hour to remove an 1/8″ of hardened edge. Have to be real careful around the quirk, and don’t burn the steel.

Shaping the Curved Bevel

Shaping the Curved Bevel

Sharpen and Hone the Cutter

Shaping is not sharpening. You need finer grits to create a cutting edge. Flattening the back is the same exercise as for any other plane blade or chisel and I honed the quirk by setting the blade up in a jig. These narrow blades are not happy in the cheap side clamp honing jigs. I found the best way to clamp one up was to lay the blade flat on the rods that connect the two sides of the jig. Check after every adjustment that the cutter is still tight against the rods. I honed the quirk first by using the jig just at the edge of my stones. Then did the flat on the other side, then the concave edge.

Bead Cutter Locked in Side Clamp Honing Jig

Bead Cutter Locked in Side Clamp Honing Jig

Here’s how to set the side clamp jig for the proper angle. Lock the protractor at 30 degrees. Hold as in this photo, when the edge of the protractor is flat against the back of the cutter and the beam of the protractor just touches the roller, the jig is at 30 degrees. Slide the cutter back and forth until this happens then tighten the clamp screw. This technique will work for any plane blade or chisel.

You have to do this for each of the three edges on the beading blade, one setting will NOT work for all.

Adjusting the Guide for Proper Angle

Adjusting the Guide for Proper Angle

Now to the actual honing of the concave surface. Clamp a dowel a bit smaller than the curved opening in the bench vise. Then hold a quarter sheet of sandpaper around the dowel with one hand while sliding the blade back with the other hand. Repeat, repeat, repeat. I have sandpaper from 50 to 1500 grit available, mostly wet/dry lubed with WD40  and will work up through most of the grits. Remove the burr from the back on a 4000 grit waterstone after every grit change.

Just keep that roller on the dowel and it works well. Be careful not to remove much material from the inside of the quirk, else the plane will bind badly.

Sanding the Curved Bevel with Honing Guide

Sanding the Curved Bevel with Honing Guide

Smaller dowels will flex in the bench vise so I made three wooden bridges for additional support.

Collection of Dowels for Various Hollow Blade Sizes

Collection of Dowels for Various Hollow Blade Sizes

Here I am using one of the bridges to support a dowel rod.

Using a Support Stick for Thinner Dowels

Using a Support Stick for Thinner Dowels

It’s a real joy to use a plane that’s properly tuned and beading planes are no exception. I’m looking forward to my next batch of boxes having beaded edges.

Tin Can Projects

Altoids tins. Aren’t they wonderful? The Standard Arduino Enclosure. I have four of them sitting in front of me on the desk mostly because I haven’t found an appropriate spot in this crowded room to store them. So I decided to gather them all and take a family portrait. There are at least six years worth of winter projects, most of them are documented elsewhere on this web log.

Tin Can Projects
Tin Can Projects

Clockwise from 12:00:

Morse keyer 2016:
The most elaborate evolution of my romance with the KC4IFB Iambic Keyer software. Uses a Teensy 3.2, has seven memories, LCD display of code sent, class D audio amplifier, software to monitor the two 18650 batteries, real time clock, and code practice.

Toastmasters Timing Light:
This project doesn’t contain an Arduino. Just a 555 timer and some switched LEDs. This was a commission from 2015.

Morse Keyer 2017:
Made to be small enough that I could listen to code practice while walking in the neighborhood. A 32U4 Adafruit Feather is inside.

Morse Keyer 2014:
This was the first and smallest of the KC4IFB keyers. It has an ATTiny85 inside, a 2032 battery and little else. Technically not an Arduino but programmable through the Arduino IDE. A Tiny85 sells for less than a dollar. It’s amazing what you can do for cheap these days.

Capacitance Based Water Level Sensor:
The current project, not written up yet. It will send water level measurements from my sump pump well to a remote alarm and display unit. Nothing inside but a Pro Mini Arduino. The PVC pipe is the sensor.

At 6:00
Capacity and Resistance Measurement Instrument:
2019 project, battery powered Pro Mini. Uses the same capacity measuring code that is inside the Water Level Sensor. I added programming to measure resistance as well.

PL Tone Generator
This was my first microcontroller project. There’s a Diavolino from Evil Mad Scientist Laboratories inside. I Downloaded the Arduino IDE and got it working in one weekend. It has a pair of thumbwheel switches used to select from a couple dozen sub audible tone frequencies which are used to trigger repeaters on the two meter ham band. I have never gotten around to installing it in the radio though.

Audio Adapter for Si5351 Signal Generator
Divides an RF signal down to audio frequency and filters that into a sine wave. It will go down to One Hertz easily. Based on an article in QST, there is no Arduino inside, just battery, TTL dividers, and MAX294 filter chips. It has two independant channels and is the most densely packed of all the Altoids tin projects I’ve done.

Si5351 Signal Generator:
A late 2017 project, with the 18650 battery it would not quite fit in an Altoids tin. That box was intended to hold a gift credit card. Has a Teensy LC inside for control and has three independent outputs, each can generate frequencies from 100 Khz to 160 Mhz.

At Center
Morse Keyer 2015
This was my final hack of the KC4IFB iambic code with memories, sine wave audio, sending decode, buffered PS2 keyboard, and code practice implemented. A Pro Mini inside but no battery.

I’ve had lots of fun doing these projects. Learned a lot – and the most outstanding thing I’ve learned is that the time required to complete a project is inversely proportional to the size of the box you’re putting it in. Thanks to all the people whose programs I pilfered to construct my own. That’s how Open Source works.


Arduino Based Capacitance Meter

Thirty five years ago I made a capacitance measuring meter from an article in 73 magazine. It’s built into a metal recipe card box about 3″ by 5″ and uses a timer chip similar to a 555 in different frequency ranges to apply AC to the capacitor under test. A microamp meter measures the current passed. Simple but each range has a separate pot for calibration. There’s two 9 volt batteries that seem to always be dead when you need the meter. It’s so old the Sharpie markings have faded out.

The 35 Year Old Capacitance Meter

The 35 Year Old Capacitance Meter

Some time ago I built a prototype water level sensor that uses the fact that water has a very high dielectric constant. Immersing a capacitor in water should result in a significant increase in capacitance. I’ve been looking for a reliable capacitance measuring circuit ever since.

I found an article on the Circuit Basics weblog that analyzed and tested three different Arduino techniques. They found the most promising method was a sketch from the Pic Tutorials web site in the UK. Test results indicated a range from a few picofarads to 1000 microfarads.  Best of all, it uses no external parts! Just two wires connected to the Arduino A0 and A2 pins. So this created a diversion from the water level project – building a stand alone C meter.

I tested the sketch on a Diavolino and on a 3.3 volt Pro Mini and it worked well. I adapted the code to output to a 16×2 LCD then started the build in an SAE (Standard Arduino Enclosure, Altoids tin) with selecting a pair of banana jacks from the junk box for the measurement connection. I spaced the jacks so I could use a standard two pin banana plug if needed, then discovered I didn’t have quite enough room to fit in the LCD.  I wish somebody would make a 3.3 volt, 3/4 size 16×2 LCD. So.. I ordered a 128×64 OLED display from Adafruit. It cost twice as much as an LCD but would fit easily and could display more information.

Locating the Adafruit OLED on the Altoids lid

Locating the Adafruit OLED on the Altoids lid

With the small display size, there would also be room for a couple of slide switches in the lid. While waiting for the OLED to arrive I parted out a small phone charger pack. Most of these contain a single 18650 cell and a small PC board with a charger and boost converter.  I’ve used them before, they are sometimes on sale for as little as $2.  The main problem is creating a hole for the USB jack and firmly attaching the PC board to  the box. The holes are a drill and file exercise. Here you can see the board is tack soldered at the top of the micro connector and at the side of the USB A jack.

Soldering Salvaged Charger Board Into the Altoids Tin

Soldering Salvaged Charger Board Into the Altoids Tin

I brought out the boosted five volt leads but since the final build is all 3.3 volt parts, did not use them.  The 18650 itself is fastened by a soldered tin strap. I also squirted in a bit of RTV sealant to make sure there would be no movement. Both plus and minus tabs are insulated with Kapton tape as I did not want the SAE to be grounded in this design.

Soldered Tin Strap Restrains the Battery

Soldered Tin Strap Restrains the Battery

The OLED is held in the lid by four screws and the Sparkfun Pro Mini is mounted directly on the back of the OLED by a five pin header soldered into digital 2, 3, 4, 5 and 6. These make the Data, Clock, D/C, Reset and Chip Select connections. Two wires complete the OLED power and ground – orange and green in this photo.

Showing How Pro Mini is Attached to the OLED

Showing How Pro Mini is Attached to the OLED

This is a top view of the arduino/OLED assembly. You can see power and ground wires on the right and leads to the A0 and A2 pins on the left. These are all that are required for the sketch to measure capacitance!

The Pro Mini/OLED Sandwich

The Pro Mini/OLED Sandwich

First trial with the measurement sketch. Very happy with the result.

First Test with 18650 Battery

First Test with 18650 Battery

Now to put it into the SAE. A rectangular opening was cut in the lid with a Dremel cutoff wheel, filed to fit. A thin plastic layer fits across that opening to protect the OLED, and four #2 screws attach the assembly.  Two DPDT slide switches fit between the Pro Mini and the measurement jacks, one switches the power leads between charger and the Arduino, the other switches the measurement jacks between capacitance pins and future resistance measuring pins. The black heat shrunk object is a 3 amp fuse.

Box Interior

Box Interior

Here the device is powered up from it’s internal battery and measuring a capacitor marked 4n7. Close enough for me.  I have a few 1% capacitors and did better calibration later on in the build.

Working with Capacitance Sketch

Working with Capacitance Sketch

Measuring resistors with an Arduino is a well developed application. Construct a divider with a known resistor and the part to measure, then use an analog input to measure voltage at the junction.  I did a spread sheet analysis of quantization errors with this technique. The calculated value can be off a lot if the measurement is anywhere near the limits of the A/D reading. My code keeps the analog reading near the center by using four resistance ranges in the known part of the divider. 100 Ω, 1000 Ω, 10,000 Ω, and 100,000 Ω. This should give repeatable measurements from 10 ohms to 1 meg ohm.

Working in Resistance Measuring Mode

Working in Resistance Measuring Mode

I also added a 10k/10k divider between power and ground of the Pro Mini. This is connected to A3 to monitor battery voltage. In this photo you can see some of the resistor measuring tree tucked under the left end of the board.  The 100 Ω resistor between 11 and 12 is used to sense ground on the measurement jacks because I didn’t have a free contact on the R-C switch to tell the processor which mode it’s in. I look for a hard ground on the negative measurement jack to indicate R mode (thin blue wire). Pin 11 goes high to apply a strong pull up to pin 12 .

Note: V1.1 The sense resistor is revised to 200 Ω and connected to A7 instead of D12. This allows detection of ground in 5 milliseconds instead of 100 with no overload on the digital pins.

Pro Mini with Battery Monitor Divider and Resistance Range Tree

Pro Mini with Battery Monitor Divider and Resistance Range Tree

I calibrated with a handful of precision caps and some 3% resistors from Frys.

Calibrating

Calibrating

This is the “Calling It Done” shot. Resistance and capacitance measuring is working, that cap is marked 330 uF but that’s near the end of analog measurement range. The circuit is not very accurate above 200 uF.

Current drain with the display as pictured is about 12.5 milliamps,  a full charge on the 18650 should run the device for a week.

Final R/C Meter

Final R/C Meter


Update Jan 29:  

Added code to check battery voltage and display an on screen alarm if less than 3.0 volts. That’s complicated because the reference for analogRead by default IS the battery, which doesn’t matter to the resistance or capacitance code because they measure a ratio not an absolute voltage. So… VREF has to be switched to the stable internal 1.1 volt supply and it turns out, that’s not a straight forward process. The Arduino.cc page on analogReference says: “After changing the analog reference, the first few readings from analogRead() may not be accurate.” You have to do an initial dummy analog read to get the change started then delay at least 5 millisec for an internal capacitor to equalize.

The battery measuring voltage divider is changed to 39k on the RAW pin and 10k to the ground pin. That puts the divided voltage in range of the INTERNAL reference.


Update Jan 31:

Banana jacks and alligator clips work great for leaded parts but surface mount, not so much. I made an adapter to make it easier to measure those tiny capacitors and resistors. An old ISA prototype card was sacrificed, (didn’t think I needed one of those these days), the fingers are about the right spacing and they’re gold plated. I cut out a small section and  firmly bolted it to a two prong banana test plug.

Surface Mount Adapter

Surface Mount Adapter

 

The small bit of epoxied on wooden coffee stirrer makes a fence to help corral the part. You place the surface mount component across two of the fingers and press down with a toothpick to do a reading. One contact finger is skipped at the right end to make a wider spaced dock for larger components like electrolytic caps. In this shot I got lucky, the capacitor stayed contacted after I released the toothpick.

Adapter in Use

Adapter in Use

Now I have to find enough pill containers to sort the hundreds of surface mount parts I’ve salvaged. That will have to wait until garage sale season.

 

If you are interested, you can download the sketch and a schematic from Dropbox.
25 Jan 2019   Version 1.0 Initial build.
26 Jan 2019   Version 1.1 Changed R-C mode detect to an analog reading.
Pullup resistor increased to 200 Ω, detect time reduced to 5 Ms.
29 Jan 2019   Version 1.2 Added code to read batt voltage and alarm if < 3V

Notes on the Schwarz Folding Bookstand

In June 2018 Popular Woodworking published an article written by Christopher Schwarz on making a small bookstand. It folds up into a neat package about 7″x3″x2″. The PW article shows the stand folded and unfolded, but doesn’t really show how it works. Several people including me, complained to PW about the lack of detail. PW responded by posting the entire article along with a short video of the bookstand folding and unfolding on their web log. Schwarz covers the construction well in the article. I will not repeat his details here but will write about the methods and tools I used, plus some minor changes in the design.

I had four slabs of walnut that used to be engraved commemorative plaques. They are 10″x14″ and about 11/16″ thick after I planed off all the text. There is a 3/8″ cove on all four edges and keyhole hanger slots cut in the back.

Rescued Commemorative plaque

Rescued Commemorative plaque

Could I salvage enough wood from one of these to make a bookstand? Of course! Could I salvage enough to make two bookstands? Probably. Could I stretch it to three?  Maybe. The first plaque I cut up did yield three bookstands but I had to glue cutoff scraps together in several places. Nevertheless, it worked and I gained a lot of understanding of what needed to be done. I proceeded to cut up a second slab after thinking through a more detailed cut plan. So if you have a 10×14 slab of walnut maybe you can use this:

Cut Plan for the Plaque

Cut Plan for the Plaque

Most of the PW project is based on sticks 7/8″ wide and 3/16″ thick. The article specifies 7″ length, mine have to be a little bit shorter, 6 5/8″ because of the cove. My table saw is currently equipped with a Diablo 7 1/4″ finish blade that makes a very thin kerf, just over a sixteenth.  I can cut a 7/8″ strip from the plaque then resaw that into two 3/16″ sticks with a little bit left over, or into a 3/8″ thick piece plus one 3/16″ stick. The back has some kind of finish that I planed off after the board was sliced up.

One section of the my cut plan produced a 3 1/2″ wide slab that I resawed into a 3/8″ and a 3/16″ section. The 3/8″ thick component was cut into six 1 1/8″ ledge parts, while the 3/16″ part made eight of the outside rail/stile sticks. For three bookstands I needed six ledges and 18 rail/stile sticks. Six shorter rail sticks form the foot and prop parts. The center frames consumed six 3/8″x7/8″x1″ blocks and six 3/8″x7/16″x6 5/8″ pieces for the frame stiles. I had to glue plugs and patches into some of the keyhole slots but I made it.

Three Bookstand Kits

Three Bookstand Kits

Initially, I made the inner frame slightly wide. I cut the two inside stiles oversize then set the final dimension by laying down two of the 7/8″ wide sticks with a thin coffee stirrer in between, marking the glued up frame to that width. The approximately 1/16″ space down the center assures room for the stand to fold completely. Gluing up the center frame was difficult. I could not keep the one inch stiles from sliding around when I applied clamps. The wads of rubber bands you can see in the above photo helped, allowing me to position the four components, then apply larger clamps when the glue began to set up.

Constructing the first group of bookstands pointed out issues with the bottom rails. Schwarz shapes the bottom of the center frame as a half circle with a full 7/8″ radius. This brings the trimmed edge very close to the lower rivet counterbores and I had a couple of those break out while setting a rivet. My second batch of bookstands has a 7/16″ radius on each bottom corner, leaving more meat in that area.

Also I decided that bottom rails don’t need full half circle rounding. They are glued to the flat surface of the ledge, so these rails only need a radius on the top inside corner.

Bookstand Glued Assemblies

Bookstand Glued Assemblies

While finishing the first batch of stands the glue joint broke between a bottom rail and ledge on three occasions. The problem is if one of the bottom rails is rotated past it’s normal open position, the ledge will contact the inner frame and put a lot of stress on the glue joint. So on the first three I redid the glue and put nails through the bottom rail into the ledge to reinforce that point. My revised design with the bottom rails only half rounded will hopefully reduce or eliminate that weak point.

Danger With Only One Side Unfolded

Danger With Only One Side Unfolded

All the rails and stiles need counterbored holes for the rivets. Accuracy of these holes, centered, and 7/16″ from the end is important to the finished stand folding smoothly. I built the specified fixture but not wanting to spend $20 on the counterbore bit Schwarz had, I dusted off a technique used in previous projects. Some router bits will make a flat bottomed hole. I used the 3/8″ keyhole bit seen in the middle of this photo. A spiral upcut bit would probably work as well. Some of the counterbores came out slightly off center when I used the router bit alone so I think the best procedure is:

  1. Start all holes with a 1/16″ pilot bit
  2. Mark all roundovers with a compass. Compass point fits nicely in the pilot hole
  3. Start all the counterbores about 1/16″ deep with a 3/8″ Forstner bit
  4. Change to the router bit and flatten the counterbore bottom
  5. Drill the pilot hole out to 9/64″

The Forstner hole will guide the pilotless router bit. Note that the top rail has holes on both ends, and its counterbores are on opposite sides. You only need to counterbore to about half the 3/16″ thickness to hide the rivets.

Fixture for Drilling Outside Rails and Stiles

Fixture for Drilling Outside Rails and Stiles

Once the round overs are marked, they can be cut out. I used a disc sander for the first batch of bookstands, but the second set of three I pared to the line with a sharp chisel and refined with a sanding block. It was just as fast as the disc sander. This picture shows some of the marked round overs. Note – top and bottom pairs here are for bottom rails and have only one corner marked.

Ends Marked for Rounding

Ends Marked for Rounding

You have to glue the ledge to the bottom rail. Note – the counterbore goes on the back of the rail, and the whole thing has to be kept square. I used leftover 7/8″ bits of wood to support the front of the ledge while fussing the bottom rail flat against the ledge while gradually tightening the clamps. I’m using Old Brown LHG so it will be easier to fix if I mess up. Here are two glue ups in progress.

Ledge and Bottom Rail Glue Up

Ledge and Bottom Rail Glue Up

While the bottom rail glue was setting up, I drilled rivet holes in the center frames. To mark the positions I fitted a 9/64″ transfer punch into one of the rails. Then holding the frame and the rail tight to a square, tapped the punch down. I then used the drill press to make 3/8″ counterbores with a Forstner bit and ran a 9/64″ bit through for the rivets. Note – on the center frame the counterbores are on the front at bottom and on the rear at the top.  Second note – If you screw this up you can make a patch from one of the thin scraps using a 3/8″ plug cutter DAMHIKT.

This photo also shows the center foot pieces in which I have pre drilled pockets based on spacing learned from the first batch of stands, 1 inch, two inches and three inches up from the bottom.

Marking for Frame Drilling

Marking for Frame Drilling

Hinges for the foot and prop that support the unfolded bookstands need to be created.  I used 4 penny finishing nails instead of the 6 penny Schwarz specified in the article. This gives a little more leeway when drilling through the pivoting part. First the holes have to be laid out. I have a gauge set to exactly half the foot thickness, and scratch the pin locations from the face on both sides of the frame. Drilling halfway from each side reduces the chance of a misalignment. Mark for drilling with an awl in the gauge scratch 3/16″ from the inside edge of the center frame rail.

The prop and foot must be firmly held in position while drilling for the pins. The foot goes on the rear of the frame against the bottom frame rail. The prop is hinged on the front of the frame against the top rail. I put a spacer cut from a playing card between the parts and the frame rails which gives some clearance for the part to swing open.

Tape the whole thing together.

Holding Foot and Prop Prior to Drilling for Hinge Pin

Holding Foot and Prop Prior to Drilling for Hinge Pin

I carefully checked that the drill press table was square to the quill. Then mounted the taped up frame in a vise and pushed a 1/16″ hole halfway through the foot and prop from both sides of the frame.

Drilling for Hinge Pins

Drilling for Hinge Pins

Next removed the 1/16″ pilot bit and replace with a 7/64″. Made 1/8″ deep counterbores on one frame stile only. This allows for the finish nail head to be sunk below the surface.

Hinge Pin Counterbore

Hinge Pin Counterbore

The final hinge step is to cut the head off one of the 4 penny nails and chuck that up in the drill press. Remove the foot and prop from the center frame and use the cut off nail to ream the hole made by the pilot bit. Also ream the two holes in the counterbored side of the frame.

Cut the taper in the prop stick. I just hogged off the wood with a chisel. Dry fit the foot and prop in the frame but don’t drive the nails in until satisfied with how they unfold. I had to chamfer the foot and prop edges above the pins to get satisfactory unfolding.

With all the parts drilled I could do a dry fit checking for interference between the moving parts. A few spots needed tuning with sandpaper or a block plane.

Successful Dry Fit

Successful Dry Fit

Each bookstand will get two layers of Watco Natural before assembly. After the rivets are installed, I will apply one more coat of Watco and finally paste wax.

Three Stands Drying

Three Stands Drying

 

Rivets. I had no experience with copper rivets prior to this project. Schwarz says they are easy and they were for the most part. I bought 75 Tandy rivets on Amazon, the PW article listed a source for a pound which would make a hundred bookstands but I only need about four for next Christmas. I think it looks better, by the way, if all the rivets face the same direction.

Now I watched my father set rivets in sickle bar mower blades a hundred times but I could never do it right. They are normally swedged with the round end of a ball pein hammer, but because in this project the rivets are recessed, you need a tool. Schwarz used a type of nail set which I’ve never seen to reach into the counterbores. I made a punch tool from the sawed off end of an auger bit by hollowing the flat end slightly with a Dremel grinder. The hollow helps to keep the punch from sliding off.

Homemade Rivet Setting Tool

Homemade Rivet Setting Tool

 

First you have to drive the burr washer down on the rivet shank. I tried two methods, both worked. The first, as shown in the article, is drilling a 9/64″ hole up the center of a hardwood dowel rod to make a setting tool. The second method uses the drill press quill to force the washer down. In the photo below left, a short piece of tubing supports the head of the rivet. The chuck is adjusted to slide loosely on the #12 rivet shank. It takes quite a bit of force to get the burr started. Note – there are lots of Youtube videos on setting copper rivets.

Set Burr With Drill Press or Dowel

Set Burr With Drill Press or Dowel

 

When the burr is firmly seated, I cut off the excess rivet shank above the surface of the wood with a pair of tile nippers left over from a long ago bathroom project. Biting the copper part way from two or three directions distorts the shank less.

Cut Rivet to Length

Cut Rivet to Length

 

I flatten the cut off shank flush with the wood surface with a rotary file bit.

Trim Rivet Flush With Surface

Trim Rivet Flush With Surface

 

The PW article shows the parts being joined lying on a steel plate while the rivet is swedged.  I don’t like that because the rivet head sits loosely in a counterbore, and just using a flat plate as an anvil will make the joint loose.  I made an anvil from a steel rod that fits inside the counterbore, clamped that in my bench vise with the bottom end resting on one of the big guide rods. Then I support the other end of the assembly at the appropriate height with a wood block clamped in a small vise.

Swedging First Rivet

Swedging First Rivet

 

I tap the concave punch holding it at a slight angle, then move the tool to a different spot. I’m trying not to hit the rivet directly in line with the shank as that may swell the whole shank. This isn’t leather, it will split the wood DAMHIKT. Just gently form the sides until the burr washer is evenly captured and the mushroomed over part is below the surface of the wood.

Swedged Copper Rivets

Swedged Copper Rivets

I fastened first the top rails to the outside stiles. Next attached the top rails to the center frame. Finally attached the bottom rail and ledge to the frame,  constantly checking that the parts didn’t interfere when folded and unfolded. It’s much easier to remove a bit of wood before the rivets are set. And the pre-applied finish needs to be completely cured or the parts may stick together – another DAMHIKT.

Swedging Last Rivet

Swedging Last Rivet

 

Six rivets done and time to test the unfolded bookstand.

Assembled Bookstand Unfolded

Assembled Bookstand Unfolded

 

A final coat of oil is optional, but paste wax protects the finish and shines it up. Merry Christmas to my three sisters, hope they don’t see this before December 25.

 

Update July 11, 2018

One of the stands in this final batch somehow got the foot and the prop reversed i.e. prop was hinged on the rear face of the frame and the foot hinged on the front face. In this condition you can’t unfold the foot to the rear as it is longer than the prop. I redrilled for the hinge pins at the correct position and in the process broke the glue joint on one of the ledges. Maybe OBG isn’t all it is advertised to be.

So I am now nailing the ledges to the bottom stiles. Thats nailing into the edge of a 3/16″ thick bit of hardwood with a very small wire nail. You must pilot drill for it. A cut off brad was not long enough to act as a pilot so I used a wire cut off a stiff paper clip as a drill bit which worked well in the drill press. I sunk only one nail near the stress point by the rivet. A number 2 screw would be better but I couldn’t find any long enough.

Here is a family photo of the final three bookstands.

Three Folding Bookstands

Three Folding Bookstands

 

Update November 8, 2018

Here is a stand made by Al Jones using a laser cutter. Perfectly radiused!

Bookstand made by Al Jones

Bookstand made by Al Jones – Laser Cut Components

 

 

More Sliding Lid Boxes – Hexagons

I had good success last year making simple sliding lid pencil boxes for the Dupage Woodworkers Club. My construction method is documented in this Weblog post. This spring I adapted the method and jigs to produce six sided boxes. The hexagonal box construction is very similar to the earlier rectangular pencil boxes so please refer to that post for details. Here I will describe the few differences.

Obviously there are two more side pieces to deal with. That’s the bad news. The good news is they are all the same length so the spacer is not required. I expected the glue up to be a big problem with the additional surfaces but with slow setting Old Brown liquid hide glue it hasn’t been an issue. There are two handle pieces to cut instead of one, and making the hexagonal lid plates is more complicated.

First, the math. The hexagonal lid plates are made from rectangular blanks. The length of the rectangular blank is the width divided by cosine of 30 degrees. To find the length of the side pieces, take half the lid blank width, add the thickness of the side stock, subtract 1/8″, then divide by the cosine of 30 degrees. Trust me, it works.

I’m using a Diablo 7 1/4″ 40 tooth finishing blade now, it cuts a very narrow kerf. I modified my regular cross cut sled to cut the lid hexagons. There is a batten tacked to the sled to establish the 30 degree angle. Actually it worked better to measure 150 degrees from the fence face on the obtuse side of the batten. This angle is critical. Next I added a movable stop to position the rectangular blank at the correct spot.

Hex Lid Jig Stop Down

Hex Lid Jig Stop Down

The stop has a hinged end, as I quickly found the small triangular cutoffs would catch on the saw blade and be launched into low earth orbit. Raising the stop lets the cutoff fall free.

Hex Lid Jig Stop Raised

Hex Lid Jig Stop Raised

The movable stop has to be calibrated to match the lid stock. I draw the hexagon onto one of the blanks then the long side of the rectangle is placed against the batten with the corner touching the stop. The stop is tweaked until the blade cuts on the line. I cut the marked blank half way to see how it’s going, then loosen the stop screws and adjust. Once the stop is calibrated it’s simply rotating a rectangular blank until the four edges are cut off.

I made a you tube video of the jig cutting a hexagon. It’s the best way to see what’s going on.

Here’s enough lids to make sixteen boxes. It goes very quickly.

Completed Hexagonal Lids

Completed Hexagonal Lids

Cutting the six side pieces requires a dedicated cross cut sled with the blade set at 30 degrees off vertical (60 degrees from the saw table). I use an adjustable flip stop as described in the sliding lid box post. There is a note at the end of the pencil box post for Doug Stowe’s method that does not require the stop to flip up.

30 Degree Crosscut Sled

30 Degree Crosscut Sled

To calibrate the stop, make the first bevel by raising the stop and bringing the stock in from the left with face side up. Note if you have a saw with a right tilt blade, these directions will be reversed.

Side Jig Second Cut

Side Jig First Cut

Measure and mark the side length on the stock then with the stock on the right side, carefully place the mark right at the saw kerf in the sled fence. Adjust the stop to that position and cut the second bevel. Once the stop is calibrated the rest of the sides go quickly. 16 boxes will need 192 cuts. For these boxes I saved time by cutting the lid grooves in the long stock before the stock was sliced into sides.

Side Jig Second Cut

Side Jig Second Cut

The side pieces are dot marked to maintain grain direction.  Designating the two pieces with three dots for handles makes the opening side exactly opposite the starting grain discontinuity. Rabbiting the lid plates and cutting off the handles is similar to the rectangular box procedure.

Gluing the hex box is similar to gluing the pencil boxes but the assembly jig is different. It now has three sides, one adjustable to account for different sized boxes. People with six hands might not need the assembly jig.

Adjustable Hex Box Assembly Jig

Adjustable Hex Box Assembly Jig

This is the jig with a box nestled between the battens. It’s a dry fit with rubber bands. I use stronger bands cut from bicycle inner tubes for the real glue up.

Hex Box Assembly Jig In Action

Hex Box Assembly Jig In Action

These are the first couple of boxes made from construction pine during the debugging phase of the jigs. Cupped lid stock is more a problem with these than it was with the narrower pencil boxes.

First Hex Boxes

First Hex Boxes

I made a number of boxes from Cherry. These two were specially done for the Beads of Courage project. Before slicing the sides, I glued on a beveled strip of Cherry at the top and bottom, and inset a small strip of Maple in the top edge. They are about 7″ wide.

First Hex Boxes

Beads of Courage Boxes in Cherry

These are the sixteen boxes made for the club Christmas drive. Menards had glued up, 1x12x48″ Poplar panels on sale for $5, I bought two. With careful measurement and calculations each panel made eight boxes.

Completed Run Sixteen Hexagonal Boxes

Completed Run Sixteen Hexagonal Boxes

Update August 2018:

Five boxes made for the Dupage Woodworkers fall Beads of Courage project. Cherry with strips of Aspen as accent.

Beads of Courage boxes

Beads of Courage boxes

Update September 2018:

Trying a vertical pencil box design. I like it. Doesn’t take up so much room on your desk. If I make them a little bit longer, will be good to store spaghetti.

Crosscut sled not needed, just tilt the blade and use the fence. Gluing is easier because it’s all long grain but the top and bottom edges are now end grain which makes the lid slot weak. Each one of these used about 11 inches of a 1×6.

Vertical Pencil Box

Vertical Pencil Box

Sliding Lid Pencil Boxes

Sliding Lid Pencil Boxes

Update September 2018:

I had trouble with getting the two lid handle cutoffs to align with each other. Sometimes there is a small step where the two glued on pieces meet. It is caused by a small amount of play in the vertical kerf of the old wooden miter box I use to cut off the handles. The Adria tenon saw is slightly narrower than the slot.

I have come up with a sure fire way to ensure the two handles are cut off the side pieces at an identical distance from the top. Note here, I always center the lid handles on the two sides with three dots so the three dot junction defines the front of the completed box. These two 1/8″ x 1/4″ wood splines fit precisely in the lid groove slots. I use them to index the two side pieces back to back before placing them in the miter box.

Two Hardwood Splines for Aligning Front Pieces

Two Hardwood Splines for Aligning Front Pieces

The splines are inserted in the top and bottom lid slots in the two front box pieces. The two pieces are sandwiched back to back.

Fitting Front Pieces Back to Back

Fitting Front Pieces Back to Back

Both three dot ends are nearest the saw handle. The sandwiched sides are shoved up against the stop, set about a half inch from the miter box kerf. Sawing down the kerf will now cut off handle pieces of identical height.

Back to Back Side Pieces Ready To Cut

Back to Back Side Pieces Ready To Cut

When I remove the cut off handle pieces, I mark the end that came from the three dot edge of the side pieces. This helps align the handles over their original side piece at glue time, which ensures there is not a vertical grain discontinuity.

Marking Three Dot End of Lid Handle Pieces

Marking Three Dot End of Lid Handle Pieces

The cut off handles are tested for fit on the lid plate tenon. I have my Miller Falls 85 rebate plane clamped upside down in the bench vise to do any tuning necessary.

Fitting Handle Pieces to Lid Plate

Fitting Handle Pieces to Lid Plate

Update October 2018

Someone on YouTube asked how the dimensions of the rectangular blank used to make the lid hexagons were derived. I made this drawing while working through the math myself.

Analysis of Hexagonal Lid

Analysis of Hexagonal Lid

Here is a circle with a hexagon inscribed. Almost everyone has done this with a compass at some time, draw a circle then step off the hexagon points by marching the compass around the circle. So sides of the hexagon are the same length as the radius and I have drawn one of the side-center equilateral triangles formed. Now I have drawn a rectangle (red) outside the hexagon representing the wooden blank needed to make the lid. What are the dimensions of the blank? The long dimension left to right is equal to twice the radius of the original circle. The short dimension top to bottom can found by looking at the small triangle formed by dropping a vertical line from the top left point of the hexagon. The vertical adjacent side of this triangle will be equal to the radius times cosine 30 degrees, and this is half the short dimension. Thus the total short side of the red rectangle is equal the the diameter of the circle (long dimension of the rectangle) times cosine 30 degrees.

More typically, the short dimension is known first as it is usually the edge to edge dimension of the board forming the blank. The long dimension will then be, short dimension divided by cosine 30 degrees.

When setting up the crosscut sled jig to cut the hexagon from a properly sized blank, the long side (bottom) of the rectangle is slid down the angled batten until the top right corner of the blank contacts the flip stop. The flip stop is adjusted until the saw cuts exactly to the right hand hexagon point which is the exact center of the blank’s short side. The easiest way to do this setup is to actually draw the hexagon on the first blank, then adjust the stop until the saw cuts right down the line. Initially move the stop in farther then necessary and make a partial test cut halfway down the line. Then move the stop out a bit at a time until the blade is cutting exactly on the line and the cut finishes at the midpoint of the short side. Beware of sawdust accumulating on the angled batten which will throw off the calibration.

Update May 2019

After making too many mistakes doing the box calculations, I finally built a spreadsheet for the hex designs. It is a second tab on my previous sheet for rectangular sliding lid boxes. There are three options:

  1.  Size box based on available lid plate stock.
    Use this if lid stock width or length is your limiting factor.
  2. Size box based on available side stock.
    Use this if you have a finite length of stock for the sides and want to make the largest box you can.
  3. Size box based on desired side width.
    Use this option if you want a box with a defined side width.
    Note side height is not a factor in the calculations. The box can be as tall as you want.

You can download the spread sheet in both xls and ods format from
https://www.dropbox.com/s/h0ckxvwsr0komyz/SlidingLidBoxCalculator.zip?dl=0

Small Router Table

Our local woodworkers club makes wooden toys every year as Christmas presents for disadvantaged children. Most of these are band sawn shapes from 2 inch stock. They are cut out, drilled, sanded, and then we do a round over on all exposed edges. I made small router tables as dedicated tools for the round over step. This post will outline my construction though I’m using photos of the finished product.

Small Router Tables

Small Router Tables

 

Small trim routers are perfectly adequate for a 1/8″ or 3/16″ round over. I have a Dewalt and a Porter Cable so made two tables.  I selected 3/8″ plywood for the table top as I had scraps on hand salvaged from (should be obvious) cable reels. Quarter inch ply might flex too much and a half inch thick table might require extending the router bit uncomfortably far. For this dedicated application, a 12 -14″ width and an 8″ depth is fine.

The first step is locating screw holes to mount the router. I removed the base plate and used that to mark the location of the four holes. Remember the router will be upside down so the mounting plate here is bottom side up. The Porter Cable router has an asymmetrical hole pattern so this is important.

Lay Out Mounting Holes

Lay Out Mounting Holes

 

Both my routers have round head mounting screws for the base plate so to match, the screw holes need to be counterbored to sink the screw heads below the table surface. Do this first with a forstner bit, then drill through with a smaller bit to fit the screw threads.  Don’t counterbore so deep that the screw attachment is weakened.

Mounting Holes Counterbored

Mounting Holes Counterbored

 

Also at this time mark and drill a pilot hole for the router bit to come through the table. Just make a hole big enough for the bearing to come through, probably 1/2″ or 5/8″. The hole will be opened up to clear the cutting edges later on.

Locate Hole for Bit

Locate Hole for Bit

 

I added a 3/4 inch bit of scrap to the bottom of the table to provide a boss for extra leg stiffness. These are attached with countersunk screws from the table top. The legs are set into holes drilled with a 10-15 degree splay angle. Splay is not absolutely necessary but makes the table more rigid when it’s clamped down. Leg dowels should be at least 1/2 inch thick and long enough that you don’t have to bend over to allow your glasses to focus on the bit. 10-12″ is good.

Support Boss for Legs

Support Boss for Legs

 

I used a piece of 3/4 stock to make the table feet. Notice the legs are offset from center to provide a larger area for clamps. I located the foot holes by assembling the legs into top, then marking where the splayed legs touched the feet.

Table Foot

Table Foot

 

This photo shows the splayed legs assembled and glued. The feet need to be parallel to the table. I ensured this by clamping the feet to the workbench while glue was applied. I then set a heavy weight on the table top while the glue was setting.

Table Legs Splayed

Table Legs Splayed

 

Getting a consistent splay angle for the legs is not difficult. I made this tapered jig for the drill press. The exact angle is not critical as long as all eight holes are drilled the same. 10-12 degrees is good. A clearly marked center line is important.

Tapered Jig to Guide Splay

Tapered Jig to Guide Splay

 

Pick a spot at the center of the table bottom and draw sight lines to where each leg hole will be drilled. The legs will lean out exactly on those lines.

Splay Sight Lines

Splay Sight Lines

 

Photos here are from my completed table so I marked another bit of scrap to better show how the sight lines are laid out on the two bosses.

Lay Out Leg Boss

Lay Out Leg Boss

 

Here you see the tapered jig clamped to the drill press table. Align the sight line on the boss with the center line on the jig and drill.

Taper Splay Jig Aligns Hole

Taper Splay Jig Aligns Hole

 

Then align and drill for the other leg.

Right Side Hole

Right Side Hole

 

The feet are drilled similarly. Here I used the upper boss to mark the sight line angle on the foot after finding where the holes go by inserting the leg dowels into the top boss. Note when you are drilling the splay direction along the sight line is opposite for the feet. On the top the legs lean out. On the bottom they lean in.

Once the feet are drilled, you can clamp and glue the whole thing together.

Duplicating Angle on Feet

Duplicating Angle on Feet

 

When the glue is set up, I assembled the router to the table. The router bearing should clear the hole at the top but not yet the rest of the roundover bit.

Pilot Hole for Router Bit

Pilot Hole for Router Bit

 

With the table clamped down in working position, I start the router and slowly raise the bit. The bit’s cutters open the hole to make a perfect zero clearance opening.

Bit Raised Through Table Top

Bit Raised Through Table Top

 

This photo shows the finished table clamped to my work bench. I sanded and sealed the top with a couple coats of danish oil, then applied paste wax. The toys slide over the bit really smooth. You have to route a bit of scrap a few times to get the bit height set exactly right.

Table Clamped to Bench

Table Clamped to Bench

 

Just slide the blank into the bit until it touches the bearing then run it to the left to do the roundover. Yo need to experiment some as moving too fast will result in a ragged edge, moving too slow will burn the wood. Needless to say, keep your fingers away from the bit, and also be aware that sometimes the bit will grab bad grain or a knot and throw the piece off the table.

Routing Roundovers

Routing Roundovers