ROHM Supra 1/32-1/2" keyless chuck "auto-loosens"

[schemer]

My seldom used as a hobbyist ROHM keyless chuck, that has spent most of it's life using a #3 drill in it in my mill, always worked great until a few days ago. I put in the #3 drill and turned on the mill at the same speed it always runs at and the drill bit fell out. So I stopped the machine and stuck it in again and it fell out again after I switch the power on. Eventually it stayed in there long enough to do the job (drilling into delrin) that it always does. I thought maybe my mill was vibrating a bit as I pushed my thumb on the draw bar and made it less noisy but that really didn't solve anything. What would cause my keyless drill chuck to all of a sudden loosen up when I power up my mill? Is that how they normally fail?
Thanks,
schemer

 

[Cadillac]

One thing to watch for is not to bottom the bit in the chuck. When loading chuck I bottom the bit out then pull down a 1/16-1/8. Giving the chuck room to pull the bit in once tightened. Just a thought.

 

[Latinrascalrg1]

Also its possible that you got some foreign material inside the jaw area that may be keeping the jaws from fully closing like normal so i would start with blowing it out as you open and close the jaws to see if that helps then maybe a full disassembly and cleaning is the ticket!

 

[Ken from ontario]

One thing to watch for is not to bottom the bit in the chuck. When loading chuck I bottom the bit out then pull down a 1/16-1/8. Giving the chuck room to pull the bit in once tightened. Just a thought.

I didn't know you had to do that with ROHM chucks, with Albrecht chuck I bottom the bit all the way then tighten, and it releases very easily, the most common problem (based on what I've learned here) is lubrication inside the chuck that causes the bit to keep dropping out .

 

[schemer]

One thing to watch for is not to bottom the bit in the chuck. When loading chuck I bottom the bit out then pull down a 1/16-1/8. Giving the chuck room to pull the bit in once tightened. Just a thought.

I tired both ways with the same results. I have used this setup for a few years and never had a problem until a few days ago. I tried it again today and 2 out of 3 tries it falls out with a few seconds and the 3 try it gradually loosens over time if left spinning under no load.

 

[schemer]

Also its possible that you got some foreign material inside the jaw area that may be keeping the jaws from fully closing like normal so i would start with blowing it out as you open and close the jaws to see if that helps then maybe a full disassembly and cleaning is the ticket!

I looked inside and dind't see any. When I pull it from the machine it norally goes into a tool box drawer but I did leave it out on top of the toolbox for a few weeks. Maybe a bug crawled into it.

 

[schemer]

I didn't know you had to do that with ROHM chucks, with Albrecht chuck I bottom the bit all the way then tighten, and it releases very easily, the most common problem (based on what I've learned here) is lubrication inside the chuck that causes the bit to keep dropping out .

Do you mean too much lubrication as in some oil got in there? Or not enough and it needs some? I have never oiled it. It is attached to an R8 adapter.

 

[schemer]

Anybody have instructions for tear down for one of these??

 

[Ken from ontario]

Do you mean too much lubrication as in some oil got in there?

That's what I'm thinking, check inside the chuck make sure the jaws are clean and dry, that's the first thing I would do. there are a few Rohm owners here who will hopefully chime in and share their thoughts.

 

[Bob Korves]

I took my Rohm apart and it was similar to a Albrecht. It was straightforward to disassemble, reassemble, and now works fine. The biggest problem with keyless chucks is too much oil/grease in them. You might try washing it out with solvent assembled, then make sure the bearings are very lightly lubed and probably nothing else. There will be enough in there to lubricate them. The shell to the jaws should be a dry fit, no or extremely little lubrication. I put oil on those parts, wipe them off completely with a clean and dry rag, and then assemble. Inertia at startup is the issue, loosening the shell under acceleration.