Thread: Tight collett

Originally Posted by Anorak Bob

I've got a small machine.

Maybe, but I'm not sure I'd call them "readily available"

There is always the R8. Though not much use for larger drills I guess?

Stuart

I regularly have the same problem with my Cash horizontla milling machine. It has a 4MT spindle and enough torque that it WILL spin the spindle after the tool has stopped, occasionally. So it needs me to tighten the drawbar properly..... The I have to hit the drawbar with a BIG hammer to get it to release - and give the taper roller bearing a BIG surprise.
I've been thinking about a hyraulic drawbar pusher I can drop on the rear end of the sprindle for a long time, but not come up with any good designs yet.
I did thread the inside of the spindle bore a couple for years ago with a fine thread and tried using a suitable 3/4" bolt to push on a special too-short 'drawbar' substitue used as a 'pushbar'. But the forces required were beyond the thread.... and I stripped the high tensile bolt's thread without budging the tool. So I had to go to back to the big hammer. One hit shifted it on that occasion....
Any solution you find will help me too!

Originally Posted by bigphill

........ I have a 30 year old Taiwanese mill/drill with a 3MT spindle. My problem is releasing the tool after use. Nothing short of a club hammer will shift the collet's grip. .......
........Phill

Phil, so you have problems releasing the TOOL. That is because you use direct mount Morse collets, inserted directly into your mill spindle.

Most folks with an MT3 spindle mill would use either an ER collet holder or a Clarkson collet holder with an MT shaft. Such collets have self releasing tapers, and it is very easy to change tools.

You still have the problem when removing the whole collet chuck, but you do that much less often than just replacing a tool. Do not use a club hammer, you risk damage the spindle bearings - use something like a dead blow nylon hammer instead. You can also make a drawbar that pushes the MT out of the spindle as you loosen it, this may mean a small modification to the top of your spindle.

Yes, an R8 spindle avoids the problem - but you may find that R8 tooling is more expensive and harder to find, unless you were living in North America where R8 is very popular. And where a mill can be ordered with either MT or R8, you will find that the R8 model has slightly less clearance between table and spindle. If you already own much MT tooling, it makes no sense choosing R8 for your next mill. Chris