How to Remove Pinion Gear from FP-9015

Hey Roboticists,

We want to remove the pinion gear that comes on the FP 00968-9015 motors in order to attach them to the AM Planetary Gearboxes. What’s the best way to remove the gear without damaging the output shaft?

I saw a thread from a few years ago that mentioned doing something similar, but was wondering if a better solution was out there.


The ‘right’ way to remove the pinion is to use a Pinion puller similar to this one:

You should be able to find one at your local hobby shop, tell them you need a pinion puller for a 500-series motor - cost should be less than $20.

The alternative - which is really just a wilder implementation of a pinion puller - is to cut a slot into a piece of steel (or similarly rigid material) such that it’ll fit snugly around the axle, between the pinion and the motor, vise the piece with pinion up, motor down, then use a mallet with a pin punch to drive the motor out of the pinion.

Another alternative is to break the pinion gear (assuming you won’t need it), using a nut splitter, or even a hammer and cold chisel and an anvil. The hammer method can be hard on the motor, so use it as a last resort.

This method is acceptable in a pinch, but it can damage the motor. I used this method to remove pinions from about a dozen tetrix motors last year and seemed to have damaged the bushings or some other internal part on one.

Agreed, if you are going to try this one, be VERY careful, as you can damage the motor and potentially yourself ::ouch:: The best way to do it is having an actual pinion puller, the “right tool for the job.” I believe the phrase goes, “if it’s hard to do, you’re doing it wrong.”

Thanks all, we ordered a pinion puller from Amazon.

This is the method I’ve always used. I usually take a dremel with a cut-off wheel and cut a deep slot, nearly to the shaft, along the length of both sides of the gear (180 degrees apart). This makes it very easy to split using a hammer and chisel.

Pulling the pinion is the easy part. Putting the new one on is where you can easily bend the shaft. I recommend making a fixture to hold the motor square and use an arbor press with a faced push rod and relief hole larger than the shaft so the clearance hole will allow you to press the pinion to the proper height. Never press on the pinion if the shaft is not exposed, as this will Guarrantee a damaged and unusable motor. :slight_smile: :slight_smile:

We have a mentor who is retired from the Motorola machine shop. He made a jig using either two pieces of steel or a single piece with the notch and set the motor and jig into a vise. He then used a pin punch in an arbor press and simply pushed the shaft out. It takes some patience but it comes out without damage to either the motor or the pinion.

If you don’t have a pin punch or it’s too long, I’ve sacrificed a twist drill smaller in diameter than the motor shaft (usually a number-series drill), cut a piece off the end and used it to with an arbour press. Good idea to hold the piece of drill with a pair of thin-nosed pliers.

I’ve never tried this method, but using a flame to heat the pinion works for pulling one off or putting one on in this video: