Help with gears

[Mem10]

Hello, I’m trying to use stock gears in my engine project but find that they need machining to work. Can anyone explain a good way of holding a gear so the interior can be machined out without destroying the teeth. It also needs to be threaded. I’m thinking a split mandrel with a clamp that reduces it size may work. Any ideas would be appreciated

 

[ChazzC]

Hello, I’m trying to use stock gears in my engine project but find that they need machining to work. Can anyone explain a good way of holding a gear so the interior can be machined out without destroying the teeth. It also needs to be threaded. I’m thinking a split mandrel with a clamp that reduces it size may work. Any ideas would be appreciated

Clamp to faceplate or clamp to a rectangular fixture plate and hold the fixture plate in the 4-Jaw (makes it easier to dial in the bore. Use spacers between the gear & faceplate/fixture plate.

 

[gbritnell]

Take a piece of round aluminum a little larger than the OD of the gear and half as long as the jaws on your chuck. Put the stock in the chuck and mark the number 1 jaw location with a marker. Now bore the stock out. The first diameter smaller than the OD of the gear and the second diameter so the gear will just slip in. Now remove the stock and saw through 60 degrees away from your mark. Now place the gear in the sacrificial collet and remount in the chuck lining up the mark with the #1jaw. Most chucks will repeat very closely to the same diameter stock. You can run an indicator on the face to get it dead square, if required. Now do you machining.

 

[michael-au]

This is how I have held gears to be machined, The recess was just under size but aloud for a nice push in fit, and with light cuts the gear did not move
You could drill and tap a hole for a grub screw in to the side so a pointed grub screw could be very lightly screwed down so the gear will not spin when tapping it
Or as above post says cut a slot to pinch the gear

 

[Richard Hed]

I had two bevel gears that I had to bore out the center. It was easy to do, but I don't remember how it was done!

 

[a41capt]

For the lathe, I use a 4 jaw chuck and dial in the bore with a dti. On the mill. I center using a coaxial indicator and either a boring head or an expanding reamer if the bore is already close, and if threading, using the appropriate tap with tap starter in an R8 collet.

Good luck, and accurate setup is the key!

John W

 

[danallen]

gbritnell has the right way. A shoulder on the od and a counter bore for the gear and a saw cut.

 

[Mem10]

This is how I have held gears to be machined, The recess was just under size but aloud for a nice push in fit, and with light cuts the gear did not move
You could drill and tap a hole for a grub screw in to the side so a pointed grub screw could be very lightly screwed down so the gear will not spin when tapping it
Or as above post says cut a slot to pinch the gear


View attachment 160502

This looks like an excellent way to try. The gear is stainless steel 32 tooth, 48 pitch. If I machine out the center of the sacrificial collet first it should clear the tap. Great idea. Thank you. My Dad was a master machinist but sadly he passed in 2009. Nice to have someone to ask. Thanks again

 

[djc]

Should we highlight the potential problems with the OP's stated "needs to be threaded"?

It is not clear from the post whether the threads are intended as the sole means of both securing and locating the gear.

If that is so, there is a good chance that it will not run concentric to the shaft on which is mounted. A small register on the gear, to locate on a similar register on the shaft would be a better-engineered solution.

Is it too obvious to mention that the rotation direction of the gear could have adverse effects on a threaded connection?