How do they do this?

[deeferdog]

I have two small DC motors that appear identical physically but differ in output power. I would like to change the the small spur gear with the brass spiral gear. For the life of me I cannot see how they are attached to the shafts. Both motors are designed to operate in both directions so I assume that they would not be threaded onto the shaft. Would a press fit have sufficient holding power over the life of the motor? The one with the spur gear is from an electric screwdriver and drives through a double planetary gear set, I imagine that it would be subjected to fairly high loads. Normally I would have expected a key or at least a grub screw but they don't appear to have these. Could they have been glued on? All this leads to the question, "How to get them off without destroying anything".
I would really appreciate any suggestions as to how to go about this before I reach for the large ballpein hammer and cold chisel. Cheers, Peter.

 

[gld]

Probably pressed on with some kind of glue.
Use one of these to remove
https://www.micromark.com/Miniature...MI58Del___3wIVhrjACh24KQT4EAQYAyABEgKtjfD_BwE

 

[e.picler]

Peter, try to heat it up, if it is glued or pressed fit, you will get it loose.

Edi

 

[bazmak]

Make a simple puller and use heat

 

[aka9950202]

I have found that they are pressed on. I have removed many of the gears with a slotted metal plate to support the gear held in the vice and a drift/pin punch to drive the shaft out.

Cheers,

Andrew in Melbourne

 

[BaronJ]

Hi Guys,

The Chinese and others, like to put a dab of super glue on the shaft before fitting the gear. Often if you look at the shaft behind the gear you can see what looks like a water stain ! If so that's the glue. Standard practice twenty or thirty seconds with a cooks torch. The plastic gears and pulleys will just pull off.

 

[larryg]

Probably pressed on with some kind of glue.
Use one of these to remove
https://www.micromark.com/Miniature...MI58Del___3wIVhrjACh24KQT4EAQYAyABEgKtjfD_BwE

I made one of those from a shaft collar that had a setscrew in it. Mill off the material opposite the set screw and modify the screw by reducing the end to shaft diameter minus.

lg
no neat sig line

 

[deeferdog]

Yep, just pressed on. I made a setup for my bench press and they came off easy. If an adhesive was used it was not evident. I confess that I am surprised that this method works, I would have thought that the back and forth load applied in opposite directions would have caused the gear to rotate on the shaft over time. I have difficulty in viewing this as good engineering, more like just another modern day shortcut. Any time I've tried anything like this its always come a gutser even with Loctite. Thanks to everyone who took the time to comment. Cheers, Peter.

 

[Wizard69]

Most likely they are heat shrunk on. The shafts are awfully small to get the press fit required with cold parts. With the right fit those gears will not go anywhere. In fact I've found many of them extremely difficult to remove without damaging any thing . In the end a heat shrunk gear or pulley can be more reliable than the standard approach of a set screw and a key.

Yep, just pressed on. I made a setup for my bench press and they came off easy. If an adhesive was used it was not evident. I confess that I am surprised that this method works, I would have thought that the back and forth load applied in opposite directions would have caused the gear to rotate on the shaft over time. I have difficulty in viewing this as good engineering, more like just another modern day shortcut. Any time I've tried anything like this its always come a gutser even with Loctite. Thanks to everyone who took the time to comment. Cheers, Peter.

 

[davidyat]

Just as a side note for the reverse. If you want to put two close fitting parts together and you don't want them to come off, use Loctite 609. I had an R8 shaft with a Jacobs Taper to fit my Albrecht keyless chuck as a dedicated unit. Didn't ever want to take it apart. For some reason, during some drilling, it kept coming apart. Put some 609 primer and the Loctite on and I don't think it will ever come apart.

 

[crec]

Press fit. We use motors all the time like that in FIRST Robotics Competitions. The pics look like what we would call a 775 motor. Just note that the 775 is a motor size spec and not a power/speed rating. We have 775s that range from around 5500 rpm all the way up to 18500 rpm. Power ratings vary as well. Usually the slower speed motors are lower power.

No heat should be required to get the gears off. Just a small puller. Did a bunch of them last year with the kids I teach for their robot intake system

You can cobble together a method to press them on (we have in the past) , but Andymark has a pressing block to put the gears on (part #am-3826a).

 

[deeferdog]

Hi Crec, thanks for the information on the motors. The one with the spur gear is from an old 12v battery drill. I use these to power the X axis of my mill. Recently I needed to power a new compound table. I had a right angle geared drive but the motor was not powerful enough, so it was just a matter of pulling off the spur gear from the drill motor and replacing it with the worm gear from the original motor and re-assembling the geared drive. The pics explain it better. Once again, thanks to you and all the others for the help. Much appreciated. Cheers, Peter.