Digital Diary Detailing Datamancer's Deeds

Don’t you hate how tool companies change the design of the batteries on their cordless power tools every 2-3 years, forcing you to buy entirely new tools because they’ve discontinued your old batteries? Yeah me too. Instead of throwing away perfectly good tools every few years, I like to save them in my scrap box for use in future projects. Power drills in particular are a great source of very strong electric motors (with transmissions) with tons of uses in robotics and hobby electronics projects. One of the things I’ve had sitting in my junk box for a while is a very small cordless circular saw that has adjustable depth and cut angle. Often in my line of work, I have a need to make very small cuts and miters on tiny moldings and other small bits of wood, so I thought it would be really cool to turn it into a mini table saw.

Click “More” for a lot more pics and build details

First I opened the case on the circular saw and fished out the wires to the trigger switch and motor, then cut off all of the superfluous plastic junk like the handle and battery port.

I found an old battery and charger that I thought still worked somewhat (I remembered the battery being able to hold a charge, but just not for very long), stripped the plastics off and exposed the wires for testing. I didn’t have the proper security bit to open the case so I *VERY CAREFULLY* cut through the screw anchors holding the two pieces of the plastic shell together, certain to not nick the battery cells or wires in the process.

After I used the voltmeter to find the proper wires, I saw that it was charging steadily.  You may notice that this isn’t even the proper battery that goes with this saw, but these tools seem to be pretty forgiving when it comes to mixing voltages and you can usually get away with a volt or two in either direction, especially if the tools are only being used for short bursts of work. This saw is rated for 14.4V and the battery is 15.6V, but actually reads on the voltmeter at around 16.6V. The charger doesn’t put out enough amperage to run the tool on its own, so by keeping the battery in the circuit, even if it only semi-works,  you’re almost making it act as a giant ballast capacitor like in a florescent light fixture, providing the immediate juice it needs to get the tool started.

Next, I dug out a piece of scrap 1/4″ oak for the first layer of the table top. I adjusted the blade depth on the saw so the blade was all the way up (or “down”, now that we’re thinking in tablesaw terms) , then mounted the saw to the wood with some glue and a few taperhead bolts. I put the tapered bolts into the tabletop from the top side, countersinking the holes so the bolt heads lay flush with the top surface.

After the saw was firmly mounted, I hooked the saw directly up to the battery momentarily then lowered the blade so it sliced through the top board, making a tiny slit that’s almost exactly the kerf (width) of the blade. After that, I measured out a few more pieces of 1/4″ oak for the top of the table and spaced them about a 1/2″ apart to leave channels for the table saw slide (borrowed from my Ryobi belt/disc sander) and rubbed a littlw wax in the channels to keep everything sliding nice and easy. I glued the strips of oak down right on top of the flush-sunk taperhead bolts that hold the table saw onto the underside of the tabletop.

I then stripped the case off of the battery charger and found that the power supply electronics were confined to a nice, simple rectangular circuit board with convenient mounting locations.  I had to find a good mounting location that wouldn’t interfere with the swing and tilt of the saw, so I put the battery off to one side and the power supply on the other.

The charger power supply is mounted on small rubber stand-offs and the only other modification I made was to unsolder and flip the LEDs around to the other side of the circuit board because I noticed that I could reuse the little LED lenses from the charger case and shine the LEDs out through the front of the wood, allowing me to see the status of the charging process.

I soldered wires directly to the old battery tabs and ran them to the corresponding wires on the charger, as though the battery was permanently on the charger dock. I also hooked up an on/off  switch to the front panel which cuts the circuit between the battery cells and the circular saw (I cut the old trigger switch from the saw completely out of the circuit).

After that, the only thing left to do was to cut a little bit of space out of the oak so the blade can angle up to 50 degrees to cut miters. Waiting until the end to do this let me cut out only as much wood as I needed so I could keep the clearances of the hole very tight.

Since most of the time I’ll probably be cutting with the blade straight up, I made a little filler plate to sit inside the hole left over. This involved a little bit of tricky shaving and carving with the ol’ Exacto knife, but I was able to make it sit perfectly flush with the wood with the help of some sandpaper.

And there you have it, a lighter junk box and a handy little mini-benchtop circular saw for small detail cuts.  Total cost – $zilch

-~Doc~-