Sourcing gunmetal for leadscrew nuts.

7/16" x 10 tpi square/acme thread is going to have a very small hole up the middle, necessitating a small and bendy boring bar for screwcutting. You might be best off using a tap, maybe rough out the thread form via screwcutting first. Or even screw cut a V thread to suitable dimension and then finish off with a tap. Tracy Tools does a lot of those types of tap for not too much loot. Be sure whether you want left or right hand thread before ordering though.

LG2 machines yes much like mild steel or even a bit easier thanks I suppose to the lead in it. Flat topped tool bit though. It's your tougher phosphor bronzes and the like that can be tough to machine.

Might pay to check the slide lock on your shaper too. If it is not clamping the tool slide solid while shaping is taking place, could be transferring too much load to the leadscrew which might account for your worn out nut.

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I’m guessing that he probably will, Hopper [*]

MichaelG.
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[*] Quote from previous page:

From what has been said, I might as well make a couple out of brass and be done with it! Much to my surprise I already have a 7/16" X 10tpi Acme tap in my collection, so all I need is a lump of brass.

Hello Hopper,

Yes indeed, I will be using a V tool to rough out and a tap to finish it. I doubt that my eyesight would be up to grinding an accurate HSS tool to ACME shape. Well fractionally narrower than a true ACME, so I can clean up the flanks if necessary.

You make an interesting point about the locking mechanism. I never thought of that. It could explain why there is so much radial play in the nut. There appears to be more radial wear than axial, something I have not seen before.

Thanks again,

Andrew.

You're welcome. Have fun with your old machine tool, and post some pics when you get the job done. Sounds interesting.

Hello Hopper,

You were bang on the money! The slide lock appeared to be working, but was in fact not clamping the slide. That explains the gross radial wear on the nut Thanks for pointing that out, otherwise the replacement nut will go the same way as the original.

Andrew.