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CR 12L14 internal stresses causing bowing after machining shaftHelpful Member!(2) 

dfoxengr (Automotive) (OP)
29 Mar 12 16:02
I am having some issues with keeping a machined 12L14 shaft straight after machining. The shafe is about 3/8" and a flat of over half the diameter is machined out of a section of the shaft in order to create a spot for a plate to rest on. While not being the best idea to cut over half the mat'l thickness out, that is what I have to work with and it can't be changed.

After these are machined there is a bow in the shaft (always away from the cut) and each shaft has to be straightened which is time consuming.

I am wondering if there is another material I can use that will have less internal stress but still be machinable. These are also moly or teflon coated afterwards.

Thank you.
dgallup (Automotive)
30 Mar 12 8:48
I would stress relieve before machining.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

metengr (Materials)
30 Mar 12 9:05
Agree with the above recommendation.
Helpful Member!  TVP (Materials)
30 Mar 12 9:34

You are almost certainly using cold-drawn bars as the starting material.  When you make the large cut, it relieves the stresses that have been induced by the cold drawing operation.  Options to pursue include the following:

1. Stress relieve prior to machining as suggested previously, or purchase the bars already stress relieved.
2. Use hot rolled bars instead of cold-drawn.
3. Use cold-finished bars that do not involve drawing, ie turned/peeled or turned and polished if you need improved surface.  Other options exist (use link below for more info):

Helpful Member!  dfoxengr (Automotive) (OP)
30 Mar 12 11:45
Yes they are cold drawn bars. Thank you all for the suggestions.

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