Removing pinion gears from old NEMA 17 motors

[motoki hayashi]

Hello, Resistors

I have just purchased a printrbot kit (low cost rep rap that was featured on kickstarter a few month ago).
My plan is to "pay-as-I-go" without paying extra, so I settled on a set that includes printed pieces and vitamins (nuts, bolts, bearings, but no electronics or hot end).  After years of just contemplating 3D printers, I think it's a good start.

Anyway, I have just purchased a set of five NEMA motors from a decommissioned CNC machine hoping to get started.
Problem is, they all came with wrong pinion gears and they aren't fixed with worm screws.  Bargaining wasn't such a great idea...

My desperate google searches pointed at two tools that can remove pinion gears.  One is a pinion puller, and other is a nut splitter.  Pinion puller seemed more ideal, but hobby grade puller wasn't a match against those pinions even though it's designed to accommodate the 5mm shaft.

So, I am shopping for a heavy duty nut splitter now, but I wanted to ask you guys if you have similar experience, or have better ideas??

Thanks,
Moto

[Michael Shiloh]

Can you cut them off with a cutoff blade mounted to a dremel-style tool?
be careful not to scar the shaft, although you shouldn't need to cut all
the way: once you cut almost all the way through the pressure should
make them pop open.

note that i've never tried this, so i don't really know what i'm talking
about :-)

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Michael Shiloh
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[Darcy Whyte]

Dremel can slice anything off.

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[Dan Lavin]

I have done this fairly often using a piece of steel L and a pin punch.

First, cut a notch in the L such that it can slip between the pinion and the motor.  Then suspend the motor from the L by the pinion and use the pin punch to drive out the motor shaft.  Do not substitute a center punch for the pin punch.

This method saves the motor bearings and keeps metal shavings out of the motor.

[motoki hayashi]

Thank you all for the tips.

So I am imagining a jig built with two pieces of metal plates screwed on a piece of scrap wood which will then be attached to a table by c-clamps.

I am still unsure if the pinion would budge though.  These pinion looks to be heated before it was installed and it's rock solid.  I was inclined for a dremel solution, but hammer should be mightier than my pinion puller with a 6-inch handle.  I will give this a go first.

Then again, I don't own a lot of tools (I don't even own a hammer at the moment), so I will be back out shopping.  Depending on what I find at hardware stores, on-sale Dremel set might be more cost effective and a quicker fix for me.  However, the issue with metal shavings does concern me a bit.  How bad can it be?

[Rob Graham]

Automotive parts shops sell or rent a tool call a gear puller.  It hooks underneath the edge of a gear and then pushes a pin though the middle.  It's used to pull pinion gears off of shafts in differentials.

$5 on Google, but the 3 tooth ones work better, they don't slip off as easily.

http://www.google.com/products/catalog?q=gear+puller&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=8009454050924908911&sa=X&ei=V4ViT5HvIuHL2QXk_fHRCA&ved=0CJYBEPMCMAE

---

From: motoki hayashi <ra...@mac.com>
To: nycresistormi...@googlegroups.com
Sent: Thursday, March 15, 2012 6:39 PM
Subject: Re: [NYCR:Microcontrollers] Removing pinion gears from old NEMA 17 motors

[Dan Lavin]

Where are you located?  If you are in NYC, I may be help you out.