Keep ACMEs on Bridgeport Retro?

[jime]

I'm retroing my Brigeport knee mill to cut some simple parts. I'm looking to do it on the cheap with steppers. Is it possible to keep the acmes in the short term to save the cost of the ball screws???? I hope to eventually update the screws, but don't initially have the funds. Thanks! Jim

[Zumba]

Yes it is possible. However, backlash can be a problem depending on how old your machine is.

Do you have a DRO installed? I would keep the DRO for referencing. When testing your G-code files, check the DROs and see how they compare to the values on your screen. Adjust the G-code accordingly.

[holbieone]

take the acme nut out ,cut it in half so you have two nuts

thread both half back onto the screw ,insert back into the yoke

adjust the back lash with the screw that holds the nut in

this is called splitting the nut

[jime]

Thanks for the help.

The machine is an old one w/o a dro. It is in very good shape with little back lash. It was owned by an 85 year old tool maker who bought it new in '63.

Anyway, I thought If I was careful with the direction of cut I might be okay with the backlash.

[holbieone]

with back lash in the nut climb milling is not a good idea as it will always be pulling the table in the direction of the back lash causing the table to bounce around

convention mill is your best choice but be careful because the tool can pull into the finished surface

[srmaietta]

well, ballscrews are much more efficient which would cut down on the size of motros neded to move the aixs. epsecially on the Z, trying to move the heavy knee+table, I think ballscrews are the way to go. ANd with new parts, backlash can be reduced greatly. Do it once, do it right. As the 85yr old machinist would probably want it done.

~Steve

[DennisCNC]

Here is my cheap setup that I did a while back still works fine and cutting parts.
1946 Bridgeport M Head Retro WriteUp