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Worn nuts for mill leadscrew

Saga continues... I made a bronze insert and bored out worn thread on original nut. BTW. I suspect that nut already has been replaced - see radial slots accuracy.

1754575838504.png


Here is first thing that I noticed. Chips from nut were stringy and long while my bronze chips are crumbly and not forming any swarf. Sound during cutting is also quite different - hissing noise while boring nut vs. "sandy"/"grinding" while turning insert.

Here is swarf from nut.

1754576185677.png


Secondly - I couldn't make nut to get "primed" with tin/silver solder. No matter what flux or temperature - it just not soldering ...
Finally i TIGed it with bronze welding rod - barely made few spot welds.

This allow is nightmare to solder/braze/weld. What it can be? Does it looks to you as aluminum bronze ?
 
I don't know if this will help you figure it out, but in this picture the piece on the left is C954 (aluminum bronze) and the piece on the right is Everdur (silicon bronze).

Screenshot_20250807-153658.png

Real aluminum bronze ought to have enough iron in it to be able to feel it with a magnet. The "backyard" version some people make is usually just 90Cu/10Al though. Hope that helps.

The cylinder ingot we poured is likely to have loads of oxides all through the metal. Maybe that's why it is crunchy to machine. We just poured the leftover metal into an open topped mold. That and the already oxidized copper in it. But a lot of splashing and turbulence goes on to generate oxide bifilm inclusions when the metal hits the bottom after free-falling into an open topped mold. For better metal quality a sprue and gating system can control and prevent this splashing.

Here is a very long video about how to properly ram up molds for casting machining billets according to the US Navy several decades ago. It's a little more involved than the quick and dirty open topped mold we used, but if we had proper bronze that wasn't already full of those copper oxides, a mold something like he describes might have helped the insert come out nicer to machine:


Jeff
 
BTW, I'm late to this thread so sorry about that.
I have a bar of 2" and 2.5" dia Ertalyte (PET-P) that I could lop a chunk off to be used for a leadscrew nut if your bronze efforts don't pan out.
Ertalyte is similar to acetal but "better".
 
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