[CATCH22]

I don't know if this is the right place to post this or not, if not let me know.
I have a cnc knee mill and the z axis ball screw connection to the quill was really loose so I took it apart and the block that fits into the keyway on the quill is loose, the block is made of bronze is there a reason I can't make a new one out of 4140. Is there a reason why they used bronze? Also is there an easier way to just fix the worn bronze?
Any help would be greatly appreciated.
Thanks Mike

[Jim Dawson]

If your machine is a BP clone, then I don't see a problem with 4140, just keep it oiled. The original quill stop was made of steel of some kind, and when I added the Z feed to my CNC I built the new block out of 4150. They probably thought bronze would be a better bearing on the edges of the keyway, but steel on cast iron is a pretty good bearing.

[CATCH22]

If your machine is a BP clone, then I don't see a problem with 4140, just keep it oiled. The original quill stop was made of steel of some kind, and when I added the Z feed to my CNC I built the new block out of 4150. They probably thought bronze would be a better bearing on the edges of the keyway, but steel on cast iron is a pretty good bearing.

OK thanks Jim.

[machinehop5]

Oilite bronze is what it may be.. Its replaceable, the machine casting is not is my two cents of thinking.
https://en.wikipedia.org/wiki/Oilite

[CATCH22]

If your machine is a BP clone, then I don't see a problem with 4140, just keep it oiled. The original quill stop was made of steel of some kind, and when I added the Z feed to my CNC I built the new block out of 4150. They probably thought bronze would be a better bearing on the edges of the keyway, but steel on cast iron is a pretty good bearing.

Hey Jim, is there any reason why I can't move the quill up and down with everything unhooked. I had to put a bottle jack on it just to get it to move upwards a bit.

[Jim Dawson]

I don't think so. The quill should be free to slide. With everything disconnected, I would expect it to just fall out of the housing. They do fit pretty tight, but when well lubed they move freely.