Need Help!- Straightening Acme lead screw?

[sylvester1073]

Hi all,
I have just about finished my first CNC machine and received the Acme screws from the USA today. Both screws (36") have bends in them of about 1/4"- 1/2" over their span. What is the best method i should use to straighten them evenly, and will their accuracy be affected? Or am i just worrying too much?

Thanks kindly in advance,
Julian.
Ps. I will post some photos soon of my machine

[ger21]

If they don't whip, then you don't need to worry about it.
Mine were whipping, so I layed them on a flat surface, and rolled them back and forth to find the bends. Then I carefully bent them by hand. They ended up having more smaller bends, but getting rid of the major bends reduced the whipping considerably.

[arizonavideo]

I had to straighten mine and I had good luck putting them on the mill with two v blocks and an indicator in a drill chuck with the 3/8 shaft going through the indicator mount so I could use it as a press.

I used the quill and the shaft to bend the rod straight after I found the high spots.

I set the v blocks about 6" apart and turned the rod to find the highest spot and then pressed it a bit with the 3/8 shaft in the drill chuck.

I was able to get a 1/2" bend down to about .010

A drill press would also work for this.

They bend easy so be careful.