Expanding Collets

"I have a part that requires internal gripping. What are my options?"

"There are two options--the "Master Expanding Collet" and the "Sure-Grip Collet-Style Expanding Collet". Both of these can be used in a 5C or 16C spindle. The Master Expanding Collet uses interchangeable pads which can be removed and stored. This unit is opened with a draw plug that actuates the collet in the front. It is mainly for light duty machining.

The Sure-Grip Collet-Style Expanding Collet system will also work. The collets are parallel opening and have a range of .125" to 4". This system, in larger sizes, can handle heavy duty machining operations." What is the operating range of a Quick-Change collet? The operating range is ± 1/64" (.393mm) when used on multi-spindle automatics for bar stock work. The operating range of the collets when used on CNC lathes is -1/64" (.393) to +.008" (.20 mm). Note that the best grip is with a full bearing, which is at the rated size of the collet. As the stock gets larger, the collet will grip at the edges of the slots; as the stock gets smaller, gripping will be at the center of the gripping surface.
"Can I machine a workpiece without using a work stop?"

"Yes and No. The collet draws back as it grips the bore of the workpiece. Any variation in the gripping diameter will cause the part to pull back farther or less than the setup piece. If you are only machining the OD of the part, then a work stop is not necessary. Unfortunately, 99% of the time this is not the case. Typically you will be machining a face or shoulder which has a length dimension that has to be held to a locating surface. This requires a work stop.

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