Bosch Pinion

[JamesJones]

Does anyone have the specs on the drill motor pinion (pitch dia, and pitch or module?)

Joe...save us!

James
Engineer/Coach
Team 180 SPAM

[Paul Copioli]

The Bosch pinion is still metric. It is a Module 0.7 [mm/tooth) with 15 teeth. The pitch diameter is 10.5mm (Pitch Dia = # of Teeth* Module). The module is the same as previous years, just a different number of teeth.

Edit: I have been digging deeper and the module may not be 0.7, but it might be 0.75. I will confirm tonight and post my findings in the morning.

[JamesJones]

Paul, please tell me it is .7


James
Engineer/Coach
Team 180 SPAM

[Andy Baker]

Oh, phooey on that gear... our team has decided to take the gear off and put on one that fits our geartrain better. I hope that a tight press fit works.

Andy B.

[Paul Copioli]

It is a 0.7 module gear. It has a very long addendum (long teeth), but will work well enough for our purposes.

Andy,

Be very careful putting the gear back on. On last year's motor it was easy to take off the pinion, but I went through some motors putting on that darn new pinion.

-Paul

[SiliconKnight]

Okay - newbie question: How *do* you go about removing a gear pinton like that one without damaging the motor? Do you heat the thing up, etc?

[Matt Reiland]

Originally posted by SiliconKnight
Okay - newbie question: How *do* you go about removing a gear pinton like that one without damaging the motor? Do you heat the thing up, etc?

In the past we have used a press and a small 'punch' to press off/on the pinions on the motors, I would not recommend any thing that shocks the armature (aka hammer)

B.T.W (I am currently our of town) does anyone have for sure the number of teeth on the bosch motor, Paul you put in your post 15?

[Andy Baker]

Matt,

You're right (and so is Paul)... 15 teeth on the Bosch Drill motor.

Andy B.

[Tristan Lall]

One other quick question:
The new Bosch drill pinion is still 20° pressure angle, right? (Like last year's.)

-Tristan Lall
Team 188, Woburn Robotics

[SiliconKnight]

Related question: Where do you buy metric gear tooth measurement devices? I am assuming you're using a gear tooth gauge - and I can only find one that measures in DP on MSC Direct. DO you just line it up to the gear and see which one fits the best? Thanks!

-=- Terence

[Andy Baker]

Originally posted by Andy Baker
Oh, phooey on that gear... our team has decided to take the gear off and put on one that fits our geartrain better. I hope that a tight press fit works.

Andy B.

OK... we just took off that drill pinion today and put on a new pinion that was a 32 dp gear. After ruining one motor (bent the shaft a bit - too tight ID at press), we had some success in putting this new gear on.

Our new gear had a purchased ID or 0.187". First, this gear was drilled out with a 0.189" dia drill, and then a 0.191" dia drill. I'm guessing that this gives us an ID of 0.192" or 0.193" (we don't really have a precice way to measure this).

At this point, the gear presses nicely onto the drill's 4.99-5.00mm shaft. We are estimating that this provides a ~0.003"-0.004" press fit, which should be plenty tight in order for it to stay in place (no welding or pinning needed).

It "feels" right so far, but we won't know if it's right until it's put under a load.

Andy B.

[Paul Copioli]

Andy,
.003" to .004" is too tight a press fit for that shaft. I pulled off the pinion and measured it with gauge pins and the original press is .0015" which is plenty for the amount of surface area you have on that pinion. My initial calcs with just a .001" press is it can handle 3x the stall torqu of the motor. We bent several shafts last year because our press was too tight.

Just some food for thought.

-Paul

[Raul]

I agree with Paul. A .001 interference is pleanty for such a small torque. In fact we also slid a pinion on the CIM motor with just .001 interference. No need to use the keyway or collars and the keyway slot provides some extra grip.

BTW, just heat the new pinion and it will slide on fairly easily. Just make sure to heat the tool that is holding the pinion and move quickly. Otherwise it will shrink and freeze in place as soon as it touches the shaft.

[Andy Baker]

Paul, Raul,

Thanks for the feedback. Maybe I'm overestimating the amount of press fit interference we are getting. Possibly the hole we are drilling with a 0.191" bit is coming out bigger than I thought.

The gears that are getting drilled out are getting pressed on fairly easily and the motor turns like it did when it came out of the box... so it seems right so far.

Andy B.

[Travis Covington]

what are the specifics of the gears you guys are using to press onto the drill motor?

we were trying to figure out what would be a good size to replace the metric gear that it currently has

I assume you guys are gearing these motors down to match speeds with the atwood? Something like 18/5 to gear it down? what gear tooths, pitches, and degrees did you guys use to reduce the output?

I am trying to take as many notes as possible in my free time i have now to use next year when we design our motor mounts (hoping we have the same drill motors, but for expirience none the less)

thanks alot!

TC

[jzampier]

Folks,
Seems like you are expecting a drill bit to give +/- 0.001 accuracy. I would say this is probably not the case. They way we always machined holes with that precision was to
drill a little small and then ream it to the correct size. A ream will give much better accuracy than a drill bit will.
Just my $0.02

[Andy Baker]

The gear we put back on was a 14 tooth, 32 dp gear. We mated that gear with a 48 tooth, 32dp gear that was in-line with the CIM motor.

Yes, reaming would be better than just drilling... but we didn't have a reamer of this size and we just had to try what we had. So far, it has worked pretty well.

Andy B.

[Travis Covington]

Andy, what was your source for the 14 and 48 tooth 32 dp gears?

Other than that thanks for the info!

TC

[Andy Baker]

I got them from Rino Mechanical. They were not listed in the catolog, but they sold them to me anyway... go figure! They told me that they were to be delivered in 1 week, and they took 10 days... not too bad for some hard-to-find gears.

Andy B.