Low spot on milled surface?

[digiex-chris]

So if you do an angled cut you'll generally be asking for trouble?

depends on the cut, the stresses in the material, the size of the material, and tolerances of the project

But generally, cut the bar to length, face the ends, leave the top bottom and sides alone except for some through holes, and it'll be fine. Anything else could be a crap shoot. I use a lot of cold rolled on my lathe because it's not a problem with cylindrical parts. Removing the same amount of material all the way around guaranteed.

For some stuff I can't tolerate any warp that I can measure. Like a scraping straight edge, I use well seasoned cast iron because I can't tolerate 0.0002" over 12" and want it to be as temperature stable as possible. But the fixture I just made to drill a bolt pattern in an RC motor mount, it can be off by 0.025 over 2" and not matter. I used cold rolled and didn't even inspect it for warp.

 

[zoltan]

Success! After taking several more shallow passes it's flat enough for my project. Thank goodness. Also, now I know better than to use cold rolled again.