Drawbar question

[sundown57]

i have a Bridgeport knock-off mill. ( machinist Unipower ) the drawbar is one piece and the threads are getting worn its 7/16-20 threads but the hex is like 9 inches long and just turned flat where it reduces size. the replacements ones i see all have like a groove in them just about where it seats like the one in the pic. Anyone know what that groove is for?

 

[derf]

It may look like a groove, but it's just a bushing. It acts as a sort of washer and it can be removed when the threads of the drawbar get worn to gain more length.

 

[sundown57]

oh ok . i thought it was machined in

 

[machPete99]

Consider making your own drawbar, if you have a lathe, and single point the threads. That way its dead on concentric and you can spin it easily with the palm of your hand. Really makes a difference on collet changes.