The guy mentioned the batteries "didn't hold much of a charge", an understatement if there ever was one as they were absolutely ratted. It didn't worry me much as I figured I had 3 motors to have a bit of fun with.
But then I thought, why not try and see if I can plug the batteries from my good drill into these tools.
Just to put the cart before the horse a bit here, you can see my files at Thingiverse!
Without further ado, here's how I used a 3d printer to up-cycle some old tools and with a bit of work, you can too.
Step 1: How to Make a 3d Printed Cordless Drill Battery Adapter
You're going to need a detailed model of your dead batteries, and an idea of how it all goes together.
Mine was held together with a few long screws so it was a simple matter of removing them then breaking a few solder joints. Batteries are dangerous so this step shouldn't be attempted lightly.
I really can't stress this enough. Be VERY careful.
Step 2: How to Make a 3d Printed Cordless Drill Battery Adapter
This needs to be spot on. The more accurate your measurements are the better it will all work and sloppy batteries can be hazardous. I used a decent Vernier Calliper worked to about 0.1mm accuracy.
Step 3: How to Make a 3d Printed Cordless Drill Battery Adapter
You probably won't need to dismantle your good equipment. It's certainly something to be avoided.
In my case, I grabbed my good drill and used the Vernier again to make a model of the docking bit on the bottom of the handle.
Step 4: How to Make a 3d Printed Cordless Drill Battery Adapter
This is going to take a little bit of imagination and some jiggling about with the two models you've made.
In my case I saved a bit of time and a lot of effort by reusing the dead batteries male stalk.
The dud battery also had a nice flat area on the bottom, but a lot of wasted room in the bottom half, so I reduced that in size.
Step 5: How to Make a 3d Printed Cordless Drill Battery Adapter
I got some friends at my local hackspace to help me with the printing, but you could also use a service like Shapeways.
All my parts slid together pretty well, but I topped it off with superglue and screws.
So now I have a circular saw and reciprocating saw while I'm away from home. I didn't bother converting the drill as I already have one, instead I'm going to use it's motor for a portable mini-lathe.