Newbie- Measuring in Collets

[JWB_Machining]

Hey,

My previous thread I was talking about how I had to machine cylinders that are as close to a 2:1 Length to Diameter Ratio as possible. I am holding these cylinders in a 5C collet so as not to ruin the finish on them. My one issue is how can I measure the length of this cylinder without losing my work offset? My current plan is to Face both ends, take it out of the collet measure it, then put it back in and reset my offset and face off the rest that I need to get the desired length. Resetting my offset though makes me think I won't be able to stay within .001 tolerance like I want to. Anybody have tips? To set my offset I plan on using a shim to press between my tool and my workpiece and setting the offset as the tolls position plus the shim thickness, this is how I set the tool offset off the chuck face but I figured I'd throw it out there if anybody had some common sense solution I'm not thinkg about.

[Geof]

Many 5C collets have an internal thread at the back end. This is to install a stop provided your workpiece is shorter that the collet. You can buy the stops or you could thread up your own as an exercise in thread cutting.

If your collets do not have the internal threads either buy new ones or simply make a plug and pin it in place.

In both cases of course the threaded or pinned stop insert has to be apped for a length of threaded rod to use as the actual adjustable stop.

[JWB_Machining]

Is there any particular brand of Collet Stops that people recommend or have had success with? I did one quick search on MSC for them and Found I can get an dividual stop for $35 or an entire Set, I'm using a TL-1 so if the difference is that certain stops can hold tighter tolerances I guess it doesn't make much sense to purchase a stop that's "tighter" then my lathe is.

[PixMan]

For a tight tolerance on length, you really should be looking at "dead length" collets.

Check with Hardinge, they'll be your best delivery.

[Andre' B]

Just to clairify things the "dead length" is normally a feature of the collet chuck, not the collet.

There are some special collets that will give you this feature in a normal spindle/chuck.
http://www.roviworkholding.com/shop/?cart=6306&cat=25&
http://www.roviworkholding.com/shop/...hp?prod_id=101