How to best Chuck a narrow gear

Hedghog · May 28, 2020

I bought myself some gears that were missing for my lathe. They are too wide so i have faced them down to correct width, 10mm a little bit less than 1/2 inch. They come machined with a fixing "grip" approx 25mm or 1 inch on one side so this was not any problem. Now i have to turn the gear arround and part off this "fixing grip part" and i do not get it how to fix the now narrow 10mm gear in my 3jaw chuck to get it true...?
Any ideas for this would be appriciated.

PeteM · May 28, 2020

Machinable collet is one solution. If your lathe takes 5C collets, I like and use the "JFK" type with a steel 5C portion and a replaceable / machinable aluminum bit in sizes up to 4" or so. If all you have is a 3 jaw chuck, you could machine up your own sort of collet out of a bit of aluminum round stock to hold around the gear teeth while you face off the nub. Mill, of course, another option. The gear wouldn't care if you cleaned up the face with something like an abrasive belt or disk.

MrStretch · May 28, 2020

MDF faceplate?
Mount a piece of thick MDF to a faceplate and turn a recess that the gear fits into snugly. Take light cuts.
I do this when making new clock wheels. After cutting the teeth, cut a fresh recess, snap in wheel and rebore the center. A trick for making sure yer new wheel is concentric.

Rickyb · May 28, 2020

Hedghog said:
I bought myself some gears that were missing for my lathe. They are too wide so i have faced them down to correct width, 10mm a little bit less than 1/2 inch. They come machined with a fixing "grip" approx 25mm or 1 inch on one side so this was not any problem. Now i have to turn the gear arround and part off this "fixing grip part" and i do not get it how to fix the now narrow 10mm gear in my 3jaw chuck to get it true...?
Any ideas for this would be appriciated.

This is essentially a facing operation. Concentricity is not important but parallism is. Make a split ring to fit the od, and use parallels to set the back side then go at it. Facing rather than parting ma be a safer option. Yah, take the parallels out before you flick the switch.

johnoder · May 28, 2020

Make yourself a an expanding mandrel on the end of a piece of stock in the lathe - have it fit the bore, and have a shoulder for the back face of the gear to sit against. Hack saw lots after tapping with small taper pipe type = expanding mandrel once you screw in a pipe plug

ratbldr427 · May 28, 2020

I have to do a lot of that kind of stuff.Sometimes as Johnoder says.But nothing is as simple as turning up a press fit arbor.A -.0005" to -.001" fit is all you need to face that.Heat to drop on and to remove with no stress.

dian · May 29, 2020

if you have several then mandrel as above. you can thread it straight and modify a screw to expand it.

the press fit arbor might give him problems if not hardened for a larger number of parts.

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How to best Chuck a narrow gear

Hedghog

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johnoder

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ratbldr427

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dian

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