Making a replacement gear for thread dial indicator

I'm currently fixing a number of issues on my recently acquired Colchester Bantam 800 lathe; one of the problems I've found is that the gear on the
thread dial indicator has a tooth missing. I don't think that it's repairable as it's some form of white metal (Mazak perhaps?) so I need to make a new one. I've read of people using a tap as a hob for worm wheels and it occurred to me that this might work for this application but I'm wondering if it's going to be difficult to cut with an Acme form tap; the second problem would be where to get a 1 1/8" x 4 TPI Acme tap for a reasonable price. The gear is 16 teeth and circa 1 1/4" in diameter. Martin
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Those gears work okay even when badly worn or misshapen and I am not sure it would not work properly with a tooth missing. I have seen straight spur gears used which did not fit the leadscrew at all well. It does not take much contact to rotate the thread dial. I have not tried it but I suspect you could cut a new gear from soft material by gashing a short section of the leadscrew at the end and using it as a hob. Otherwise you might get any kind of 4TPI tap or bolt and use it as a hob.
Don Young (USA)
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In article <t4-dnYV9esmWO-PVnZ2dnUVZ snipped-for-privacy@posted.worldwebinternetservicesprovidei

Whilst I agree with Don, if it were me I would take the thought a step further and try a repair. I would cut a slot in the gear where the missing tooth isn't, so to speak, and insert (using Araldite) a sliver of brass (or similar) a bit bigger than the teeth, then file it down to approximately the shape of the teeth. As Don says, the power transmission is negligible, and any tiny deviation in angular positioning due to deviation in shape would not be noticeable in this application.
David
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David Littlewood

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Thanks David, that sound favourite so far. Martin.
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wrote:

Hi If you get stuck, contact me , I can probably make you a new gear. Peter
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Thanks Don but I don't fancy gashing the leadscrew and I can't think of a lashup that would enable me to use it to cut the gear anyway, the through bore of the headstock is too small to try getting in the lathe! I'll dig around for a 4 TPI tap but they are a bit thin on the ground in my workshop, maybe I'll find one on fleabay. Martin.
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wrote: would be where to get a 1 1/8" x 4 TPI Acme tap for a

Try Tracy tools
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wrote: would be where to get a 1 1/8" x 4 TPI Acme tap for a

Try Tracy tools
I've already checked the website and they don't have them that large; thanks anyway. Martin.
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