loose collets

[blockmanjohn]

I have a Uni-Vertical bench top milling machine which probably dates from the 40's. It has a Bridgeport head, serial number H345. It has Hardinge 2VB collets. My problem is that there is no way to adequately tighten the collets so the end mills don't slide up, even when taking very small cuts.

I cleaned the inside of the collets, and the end mill to no avail. To give you an idea of how loose they are, I can place the work up tight to the end mill and still crank the z-axis upwards with very little resistance. The tool just slides up into the collet. I also pulled out the closer and cleaned the threads. No luck.

I have no idea how to proceed. If any one has some idea of how to fix this I would really like to hear from you. Thanks, John.

 

[mcostello]

Does it have the right draw bar? Are the threads bottoming out?

 

[Blogwitch]

I would suggest the same as M above.

Check that your drawbar is not bottoming out in the bottom of the collet thread.

To check whether the collet is being pulled up enough to clamp, look underneath the collet after it has been drawn up into the spindle. If the slots are closed tight together, then it means that the cutter is too small for the collet, if there are still gaps, that points to the drawbar problem not being able to pull the collet up far enough to clamp tight.

John

 

[blockmanjohn]

You guys nailed it. The drawbar was indeed bottoming out in the collet threads. A fter removing 3 threads all is well.

This machine is new to me and I don't know the history of any repairs or modifications that were done to it. I'm just glad the experts on this forum could set me straight. Thanks, John.