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Brazing teeth

Teeth missing from bull and back gear

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Grant Allen 125/03/2019 18:12:28
48 forum posts
5 photos

Hi all does anyone know if there is any instructions on here for how to braze teeth if possible as my gears are missing a few, I also want to know if the half nut can be replaced etc as worn where I could find one or someone to send to?

Grant

Bazyle25/03/2019 18:47:13
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4489 forum posts
184 photos

Grant, The best method for you is as advised on the Drummond group to drill a couple of small holes in the gap, fit mild steel rod in the hole and braze it in with extra braze to fill in the gaps a bit. then file to shape. When brazing make sure to heat up most of the gear not a point where you are working so as to avoid stress.
It is better to use soft mild steel rather than screws which will be hard and might get chilled harder in the brazing so that it is easier to file. You could even use brass screws and silver solder, though it might be more difficult to get ss to take on cast iron.

If the half nut is not jumping out of gear it is not yet worn too much to use so you have some time to learn how to make a new one.

Dave Halford25/03/2019 19:20:24
373 forum posts
3 photos

When you get broken teeth on a gear it's best to source another gear, turn the old teeth off, chain drill out the centre from the replacement gear and bore to the same size then loctite the two together - worked on my old Rockwell.

Don't be tempted to use weld to make up the teeth unless you can get almost pure nickel rods (the expensive ones) some have a fair bit of iron in them and the teeth end up very hard

Edited By Dave Halford on 25/03/2019 19:21:12

Hopper26/03/2019 08:59:45
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3529 forum posts
68 photos

Half nut repair on M-types is common. ISTR Geoff Walker did an article in MEW in the last couple years on doing his. Basically, you clamp the halfnut on the cross slide table and bore out the old thread - boring "half a hole" in effect.

Then you turn up a piece of brass shaped like a cotton reel or "bobbin", ie cylinder with a small locating flange each end, which fits the "half a hole" you bored in the old halfnut. This is then screw cut internally with a 1/8" pitch square thread to fit your leadscrew and then cut in half lengthways with a hacksaw. One half is then soft soldered into the halfnut. Good as new.

I'm sure there are pics and details on the Yahoo group, somewhere.

The rub is you need a lathe to screwcut the new bobbin. But if there is enough left of the old half-nut to be going on with, you can make the bobbin first, then machine the halfnut to fit it.

Good used gears are available via the group or on eBay too. Better than trying to fake up new teeth with brazing and a file. Which gears do you need? Back gears or change gears?

CuP Alloys 126/03/2019 09:21:48
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186 forum posts

Hi Grant.

Silver soldering cast iron to itself or stainless or copper alloy is no problem. You simply need to make a slight adjustment to your technique to ensure that you stick to the basic principle of brazing - capillary flow.

For more information see the book or give us a call.

Regards

Keith.

Grant Allen 126/03/2019 09:23:41
48 forum posts
5 photos

Hello hopper I've managed to source a bull gear as 4 teeth have gone , but still looking for the back gear that runs on an offset bar that engages and disengages ( sorry dont know what it's called). This one is missing 2 teeth but together. I've checked everything else and it just needs a thorough clean, rust removal and repainting. The last person who owned it had it for 40yrs and used it to turn metal and wood, so lots of oil soaked dust and shavings.

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