Re: [CAD_CAM_EDM_DRO] 5C collet closer drawbar threading problem

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>On Tuesday 08 July 2003 02:39 pm, Kim Lux spake:
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>>The drawbar we are making is machined from a piece of seamless
>>mechanical tubing. We've got it adjusted for zero runout.
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>>We are cutting a 1.044" OD x 24 TPI thread on the outside of a 1.250"
>>piece of tubing turned down to 1.030" This will pull on the internal
>>thread of the collet to close it in the chuck.
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>>We've threaded two of these drawbars now and both times the collet has
>>significant runout when threaded to the drawbar. Why ? The thread
>>seems to be high quality.
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Are you sure the ID thread on the collet is concentric? A lot of cheaper
collets have a steel plug that is welded or pinned into the collet body,
such that the OD threads may be concentric, but the ID ones aren't.
The ID threads are usually used to hold a collet stop in the 5C, and so
a modest runout won't cause a problem. You may have to make an
ID to OD adaptor so the same drawtube can be made to pull on the
OD of the collet. I have a strong suspicion my 5C collets would
act just like this.

Jon