drilling that chiaphua gear

We are planning to mount the chiaphua gear to a .25" shaft using a 1/16" roll pin, but we can’t seem to drill through it. We got a cobalt bit, a good drill press, and plenty of drill oil, but that darn gear is so hard that 30 minutes of straight drilling at the highest pressure possible before the bit bends got us down about a millimeter. At this rate, each gear will take us 5 hours to drill. Does anyone have any suggestions on how to cut this thing?

I’ve heard a lot of talks about how hard it is to drill that gear…

I think your best bet is to buy a gear that will mate with it, and attach that gear to a shaft instead.

Zan it worked for us i was standing there when we drilled those suckers. It only took like 20 seconds, but i dont know what type of drill bit we were using. If you need us to drill it for you give me a hollar. I will ask our machinist what drill he was using.

so we were trying to do it forever also if you could find out what tyoe of bit he used that would be great thanks

Our machinist only broke one bit. He used a cobalt bit. First he ground off the teeth to provide a good drilling surface. The robot is now driving around with both motors. Our gears are pinned to a 1/4" shaft with stainless steel spring pins.

Our cobalt bit just kept spinning in place, so we went with a carbide bit. This went through the gear like butter, and we managed to finally drill through both gears, but we broke three of the $8 bits in the process. Those things are quite hard, but that means they also are quite brittle. The trick, we found, is to drill in short pulses, as constant pressure on the drill can actually harden the metal directly under the bit.

Oh, and thanks mnkysp for the offer. I am always impressed with the level on generosity that the other FIRST teams have shown us.

Zan my team is always here for you guys. If you need any help call (310) 842-4200 ext 6059 ask for me Justin Rolnick or Ms. Swanson. If im not there She can help you.

We also had a lot of trouble drilling that gear. We finally found a machine shop that volunteered to EDM (electric discharge machining) to machine an 1/8" hole. You may be able to find a local shop to do this for you.


We drilled the gear on a mill with a titanium bit and it never broke. You just have to put alot of force on it.