R8 collet problem

[Kirkbregar]

I just recently bought a hvm728 jet mill at an auction, it's in really good shape. The problem is the r8 collet goes in so far and stops about 3/4 short from seating in the taper. Am I doing something wrong. I've read about a set screw on the side of the quill that can be backed out just wasn't sure if this is correct??

Any knowledge I'd appreciate it!!

Thanks

 

[MalR]

Yes, there’s a small screw that aligns with the keyway in the collet. It is only intended to stop the collet rotating while tightening and some people remove this screw (or shear it off by not tightening a collet properly). They sometime get burred through use and it may be this that’s stopping your collet seating correctly.


Mal

 

[rgray]

Some collets have a shallow groove. Do you have some that fit and some that don't?
Are you turning the collet to align the pin and the groove?
Flashlight and mirror to see what the pin looks like may be a good idea.

 

[RJSakowski]

We had this problem. I replaced the set screw with a socket head cap screw. I turned the screw length so it protruded enough to engage the keyway but not bottom out and the tip diameter to fit the R8 keyway, With a head on the screw, it now is impossible to have the tip protrude too far. The Grizzly mill that I worked on had sufficient clearance to clear the head of the screw but check to make sure on your machine. If clearance ius a problem, there are low profile screws and hex socket button head screws that may work.

To determine the length, I inserted a collet and tightened the screw until it contacted the collet and backed the screw off one full turn. Then I removed the collet and tightened the screw, counting the turns necessary to do that. By knowing the screw pitch and number of turns, you can calculate the the distance between the head of the screw and the shoulder. add about .060" for the protruding tip and .0155" should work for the diameter. The finished screw can then be tightened to contact the spindle which will prevent it from loosening in use.

 

[Kirkbregar]

Some collets have a shallow groove. Do you have some that fit and some that don't?
Are you turning the collet to align the pin and the groove?
Flashlight and mirror to see what the pin looks like may be a good idea.

Yes, there’s a small screw that aligns with the keyway in the collet. It is only intended to stop the collet rotating while tightening and some people remove this screw (or shear it off by not tightening a collet properly). They sometime get burred through use and it may be this that’s stopping your collet seating correctly.


Mal

thanks for the information but the only problem I see now is finding the setscrew if I lower the quill down there is no way of getting to it. I'm hoping I don't have to tear it all apart to access it

 

[Kirkbregar]

Some collets have a shallow groove. Do you have some that fit and some that don't?
Are you turning the collet to align the pin and the groove?
Flashlight and mirror to see what the pin looks like may be a good idea.

I only have 2 collets so far and neither fit they need to go up in another 3/4" I wish I knew how to get to the set screw.....

 

[Kirkbregar]

We had this problem. I replaced the set screw with a socket head cap screw. I turned the screw length so it protruded enough to engage the keyway but not bottom out and the tip diameter to fit the R8 keyway, With a head on the screw, it now is impossible to have the tip protrude too far. The Grizzly mill that I worked on had sufficient clearance to clear the head of the screw but check to make sure on your machine. If clearance ius a problem, there are low profile screws and hex socket button head screws that may work.

To determine the length, I inserted a collet and tightened the screw until it contacted the collet and backed the screw off one full turn. Then I removed the collet and tightened the screw, counting the turns necessary to do that. By knowing the screw pitch and number of turns, you can calculate the the distance between the head of the screw and the shoulder. add about .060" for the protruding tip and .0155" should work for the diameter. The finished screw can then be tightened to contact the spindle which will prevent it from loosening in use.

How do I get to the set screw??

 

[ddickey]

 

[petertha]

Maybe this will help
https://www.hobby-machinist.com/threads/935-spindle-nose-piece-removal.74301/

 

[kd4gij]

First you should be able to feel it sticking your finger up the spindle. Machine off of Corse. to get to it on most machines lower the quill all the way down. there should be an access hole to get to the screw.