1/16" Undersize hole How to "drill" (Bull Gear repair)

Kevinb71

Kevinb71

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I want to install some 1/16th x 1/4" pins in my lathe bull gear to support the new teeth. My question is what would be the right way to "drill; these holes. I would like the holes to be a light press fit, but the next size smaller bit that I can find is .0595, a #53 drill bit. .030 smaller than the pins. I intend to bronze over these to fill in the four tooth gap in my lathe bull gear and then remachine the teeth. Maybe with bronzing over the top I don't need to worry about a press fit. What are the options?
 
I assume you mean to braze over the surface? If so, everything should be just fine without a press fit. At least that is the way I would do it.;)
 
Redirish said:
I assume you mean to braze over the surface? If so, everything should be just fine without a press fit. At least that is the way I would do it.;)
Click to expand...

I agree with the above but if you want a light sliding fit, drill undersize and use a chucking reamer or a hand reamer. Never turn a reamer backwards even a little. they will dull and pack up right away. You can also buy reamers -.001 or more undersize for press fits.
 
I have not seen a reamer that small. Where do you get them?
 
Unfortunately I dont have any pics, and the situation is a bit different, but I had 4 or 5 missing teeth on the quill of my drill press. I machined out a section of the quill that just penetrated through the wall thickness at the deepest part of the cut, that was enough to completely remove the full width of the teeth, and over the length of the damaged area.
I then got a nice piece of steel that I fitted neatly in to the machined area, and I cut new teeth into that. I marked out and cut the new teeth whilst I could still hold the piece of steel in the vise. Once it was finished I loctited it into place and also drilled and pinned it to the quill.
This way you have new teeth cut into good steel and not just built up over strengthening pins and welded metal.
Would it be possible for you to just completely remove area of the 4 broken teeth, fit a new piece in, (probably would need to be welded/brazed), grind it to suit the profile of the gear and then cut your new teeth in that. Then you are not just relying on a little dab of brazing to carry the load but you are transferring it to a much larger surface area.

Cheers Phil

Edit, Was only 3 teeth, but I was able to get a couple of shots of the repair in place.
IMG_5246.jpg and IMG_5250.jpg

The little black dot in the middle tooth is where I pinned it.

IMG_5246.jpg IMG_5250.jpg
 
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I like Phil's idea much better than pins or screws because it spreads the load over a larger area and it uses steel for the repair rather than brass. You could even get fancy and dovetail the block in place with a light press fit so it wouldn't need to be welded or brazed.

Tom
 
There are just so many different ways to kill the same cat! Thanks for all the ideas.:)
 
Kevin,
Let us know how you go with the repair and what method you eventually use please.

Cheers Phil
 
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