5 C COLLET BLOCK CHUCKS

The one I have is simply a holder for the collets that fits a Jarno taper [0.60"/ft]. I am machining an adaptor to fit my 1-1/2" 8 TPI headstock. Bugs

Are they called block chucks on a lathe?? On lathes, I hear them referred to as "noses" or "closers" (snap handle or spin). At least in my semi-exhaustive hunt for a used lathe w/collet closer!

after you machine the adaptor and fit it to the 5c collet block, would you have an effective poor mans 5C collet chuck?

The collet blocks are typically used with milling machines or grinders. The workpiece is held in them in the collet, and the entire block (square or hex) can then be clamped or held for machining, and rotated for subsequent steps.

Collet chucks are another animal.

John Martin

There are several different styles, but for the lathe you would want the round type. They are normally held in a 4jaw chuck or in a 3jaw with soft jaws that you would bore to fit. Some have a screw on the front side to release the collet or a nut on the back that has to be accessed from the back of the lathe throught the spindle, or taken out of the chuck to get at. I have seen set-ups where the part is held in the collet chuck off center and then put in the lathe to machine an eccentric. We used them to hold small parts or round bar that would be a pain in a larger chuck and allowed us to dial them in perfect in the 4jaw.

So once the round type is centered in the 4-jaw chuck, can the block be used as a collet chuck?

Sort of. The ones I've seen have a nut on the back to draw the collet up, which means you would have to remove it from the chuck to change parts. If you are being fussy, this could require re-centering in the chuck every time you change parts. Also, depending on how accurate your chuck is, it may not be parallel to the spindle bore. That means you can center a part only at one distance from the chuck. All in all, it's not a very good replacement for a true collet system. A collet chuck or draw bar setup with a collet sleeve in the headstock will be far more useful.

Doug White

Dont forget the collet blocks that slip into the KDK/Aloris etc quick change holders. With such a block, you can mill, drill, cross drill, slit, drill hole patterns and offset holes, while on the lathe

I made one just to fit my lathe. Its been invaluable.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

======================== What I call collet block chucks are also called tumble blocks or tumble fixtures. See

?PMAKA=891-6015&PMPXNO=3905656&PARTPG=INLMK3 Enco frequently has these on sale as a set.

You can use these on a lathe with a faceplate to machine squares and hexes, although more generally used with a mill. You can also use as a cheap collet closer, but see below for better solution.

For lathe use an item that can provide a cheap collet closer is a vertical collet vise. You can bolt this onto a face plate. See

These also go on sale from time to time with a set of collets [X

16ths]

Many other suppliers have the same items.

Tip on setting this up is to chuck up a 1/2 inch dowel pin about

4 inches long in the tail stock and chuck up the other end of the dowel with the vertical collet vise to locate it on the face plate. Close enough for most work, and it will be close enough to use your limited range (+/1 15 thou) test indicator when you need the best accuracy possible.

Drawbacks are chuck overhang and inability to feed stock through the collet/spindle because the fixture is closed on the bottom. Collet chuck is an alternative but costs 4 or 5 X.

Hope this helps.