Metal really moved...

[Ron LaDow]

I drilled and bolted two 10" sections of 1 X 2 CRS together on the 1" edge, then drilled and bored a hole centered on the joint to make a very accurate press tool.
After boring, with one bolt tight, the other ends of the stock separated by 3/8"!
I know there are internal stresses in CR, but I wonder if this is out of the ordinary?
Thanks,
Ron LaDow
Added by edit: the hole is 2.180" D.

[This message has been edited by Ron LaDow (edited 08-05-2001).]

[C. Tate]

Ron, I have had very similar results when using 1018 crs. I built a fixture that is suspended between my rotary table and a tailstock so that I could rotate castings on the mill and retain accuracy between planes. I used a piece of 1 x 6 1018 flat bar, milled the top and then tapped 1/2-13 holes for threaded studs. When I removed the bolts holding the tail stock the fixture which is 20 inches long picked entire tailstock up off of the mill table about 125 thou. My solution was to use ductile iron for the next one. I believe you can stress releive 1018

[halfnut]

Ornery stuff sometimes, won't stay still, if you told an average person that they wouldn't believe you.

Sometimes if I think that it will give me lots of grief on the part I am making I will let it take a trip through the heat treat oven before I go home, bout 1200 deg. turn off the oven and work on it the next day.

Rosebud on torch works also, heat to good full dull red, let cool slowly.

[SGW]

It will do that.... Your experience is certainly nothing out of the ordinary. I made a gib strip out of a piece of 1/16" x 1/2" CRS a few years ago, and milling the dovetail angle along one edge made it warp about half an inch over its length.
If you asymmetrically mill a piece of CRS, it's virtually guaranteed to warp on you. Stress relieving it first (as per Halfnut's suggestions) helps a lot.

If you have a critical job, it may be worth the extra money to buy a piece of stress-relieved low-carbon ground stock. Aside from not warping, it will almost certainly machine to a better finish than the typical commercial CRS.

[This message has been edited by SGW (edited 08-06-2001).]

[Ron LaDow]

Thanks, guys.
SGW; appreciate the info on stress-relieved. Didn't need it here, but good to keep in mind.
CT; good story. I can see the eyes when the tail stock comes off the table.
Half-nut; you're right. Most people think metal is rigid. I knew is wasn't but I was surprised to measure the the distortion with a yard stick instead of a mic.