Removing Drill pinion

[Jack Jones]

Originally Posted by Rickertsen2

Does anybody have anybody have any ideas as to how to get the drill motor pinion off?

Sorry, I'm so late on this - hope you've already solved it; but here's two good methods.

#1: You don't care if you distroy the pinion;
Use a dremmeling tool with cut-off wheel. Cut as deep as you can into the pinion without cutting the shaft (lengthwise, between two teeth). Place pinion on anvil or other solid surface. Drive a cold chisel or center punch into the slot you cut. The gear will split in half.

#2: You want to save the pinion;
Get a faucet handle puller (~$7) from any hardware and a butane jewler's torch. Grind or belt sand the jaws of the puller so that they'll fit under the pulley. Cut the pin on the puller to a length of 1/2 inch and grind it to a point. Drill a dimple in the center of the motor shaft. Mount puller to pinion and apply a modest force - not too much, the puller is a cheapo. Heat the pinion with the torch. Give the puller another turn or so; when you hear a POP, it's ready to turn all the way off.

JJ

[Al Fielder]

There is a device commonly referred to as a bearing removal tool, it is a split plate that bolts together and has a small hole in the center that has a huge countersink so that it slide under a relatively small gap such as the gap between the drill motor and the pinion. The bolts are tightened and then the whole thing is put in a press so that the motor/pinion is supported (hanging from) the tool. Then the drill motor shaft is pressed out of the pinion in much the same way that the tool shown in one of the previous posts works.

I would be reluctant to cut away the gear (pinion) unless you do a thorough job of masking the motor. If the metallic dust gets into the wrong place in your motor, it could trash the motor quickly.

If you choose to press a replacement gear on the shaft of a somewhat similar number of teeth (but different pitch), stay with a .0002-.0005 interference fit (press). If you go much tighter, you may yield the gear and you could easily lose the press i.e the gear now spins on the shaft.

Good luck

[Larry Barello]

Originally Posted by Al Fielder

...
If you choose to press a replacement gear on the shaft of a somewhat similar number of teeth (but different pitch), stay with a .0002-.0005 interference fit (press). If you go much tighter, you may yield the gear and you could easily lose the press i.e the gear now spins on the shaft.

Good luck

How does one get a .0005 interference fit with the replacement gear? Are metric reamers sized .02mm under readily available? Where would I find such a tool?

Basically, I got .7 mod gears from PIC-Design to mate the Bosch to the rest of the gearbox, but I am having fits trying to get the spacing correct. No such problems with the 20dp gears from Martin Sprocket...

[Alan Ing]

Hi all, just thought I'd throw in my two cents. First of all our team (368) is taking a year off (everyone is burnt out), so unfortunately we won't be able to join in on all the fun.

Over the past two years we have been removing our pinion gears using an arbor press which has been a real pain as those gears are on pretty tight and have more than once bent our pinion removing fixture.

While rumaging through my tool box the other day, I came across a Craftsman (sears) nut splitter and all of a sudden it occured to me that this might be the easiest (destructive) way to remove it. Since I had a broken bosch motor from last year (brush assembly broke off, I decided to try the nut splitter on the pinion gear to see how it would work. After carefully aligning it on the pinion gear, I grabed the nutsplitter with a wrench so as not to put any pressure on the shaft of the motor and used another small wrench on the screw that forces the nut, or in this case the pinion gear into the anvil. In two seconds, I heard a little cracking sound. The pinion gear is hardened and brittle and with very little pressure at all, the nut splitter put a hairline crack in the pinion gear and it basically just slid off the shaft without damaging the shaft. Basically the anvil gets wedged between the teeth of the pinion and causes the teeth to split apart (the anvil fits between the teeth but does not bottom out) as you apply pressure to the screw.

A nutsplitter from Sears is about $15.00 or so and definitely is the quickest and easiest way I found to remove a pinion gear off of the bosch motor. Only a little pressure is required and but you may have to reset the nutsplitter on the pinion gear as the screw may break a few of the teeth off first.

I wish I had figured this out two years ago which would have saved us a lot of time. If anyone has an old damaged bosch, try it for themselves. It works great. Just remember to go slow and easy on the screw as it doesn't take much effort.

Again, this method will work as long as you don't mind destroying the pinion gear. Lastly, I only tried this on last years bosch motor so it might not work that well on the fp motor which has a much larger pinion gear.

If anyone tries this, let me know how it worked for you.

Oh well, have fun, wish we could be compete with you all as we never did make a robot that could pull itself up on a bar.