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



## schemer (Jun 25, 2019)

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


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## Cadillac (Jun 25, 2019)

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.


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## Latinrascalrg1 (Jun 25, 2019)

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!


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## Ken from ontario (Jun 25, 2019)

Cadillac said:


> 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 .


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## schemer (Jun 25, 2019)

Cadillac said:


> 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.


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## schemer (Jun 25, 2019)

Latinrascalrg1 said:


> 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.


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## schemer (Jun 25, 2019)

Ken from ontario said:


> 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.


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## schemer (Jun 25, 2019)

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


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## Ken from ontario (Jun 25, 2019)

schemer said:


> 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.


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## Bob Korves (Jun 25, 2019)

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.


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## schemer (Jun 26, 2019)

Bob Korves said:


> 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.



Thanks Bob. I stuck a Q-tip down in the center and a little grease or oil showed up on it. I will try what you said and clean it without disassemby first and then if I have to, will disassemble it. Now that you mention the inertia at the start being the issue, I remember I tightened up the belt a few weeks back and maybe that changed something just enough to show up this issue.


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## rgray (Jun 26, 2019)

I had a new china keyless chuck do that. I just blew it out with an air hose and wiped the inside out and it never did it again.
None of my Albrecht chucks have ever done it.


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## Iceberg86300 (Jun 26, 2019)

schemer said:


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


After reading your first post I searched & searched for a service manual.

Seems that one exists, but not "freely" on the net. If you search "rohm Supra Chuck (service, repair & disassembly were 3 terms I tried here)" you'll find a few threads. 

There are a couple users that emailed it around, and one link to a personal website which is now defunct. Tried the internet archive but it was down for maintenance. 

However, you might find that one of the users that offered or received the manual through email is still active on the forums & still has the manual.

Probably worth PMing said users to see if they're still around as it seems like proper preload & proper lubrication are important.

If parts are worn however, you will be out of luck. Parts seem to be non existent & rohm replied to someone stating that the jaws are ground after assembly, and w/o this factory process the chuck loses its accuracy when new parts are installed. 

Regards,

Steve


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## schemer (Jun 27, 2019)

rgray said:


> I had a new china keyless chuck do that. I just blew it out with an air hose and wiped the inside out and it never did it again.
> None of my Albrecht chucks have ever done it.


Good to know as I just bought a Chinese Keyless chuck for a spare along with a new Rohm like the one that is giving me grief. I haven't messed with it for a few days as I got tied up with auto and lawn lower repairs, but at least I have a plan B.


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## schemer (Jun 27, 2019)

Iceberg86300 said:


> After reading your first post I searched & searched for a service manual.
> 
> Seems that one exists, but not "freely" on the net. If you search "rohm Supra Chuck (service, repair & disassembly were 3 terms I tried here)" you'll find a few threads.
> 
> ...



Thanks Steve. I had researched what you said and ran into the missing manual threads too. I think i can handle it if need be using the Albrecht instructions. I know to mark the jaws for proper assembly into the slots they came from etc... I was just surprised as I never had a keyless chuck fail like that before and from one week fine to the next week acting up.


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## Iceberg86300 (Jun 27, 2019)

schemer said:


> Thanks Steve. I had researched what you said and ran into the missing manual threads too. I think i can handle it if need be using the Albrecht instructions. I know to mark the jaws for proper assembly into the slots they came from etc... I was just surprised as I never had a keyless chuck fail like that before and from one week fine to the next week acting up.


Yeah, pretty weird to get a sudden & repeatable failure. I'd expect it to be intermittent first.

Points towards dirt/oil finding it's way into somewhere it shouldn't be, or possibly a cracked/broken part. 

But I don't have experience with these so it's just a guess.

Although it could have worn something in a single spot by always using the same drill. Maybe try a larger/smaller drill to see if it still releases on startup. 

Regards,

Steve


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## RJSakowski (Jun 27, 2019)

Just a wild shot but you didn't have the mill in reverse, did you?


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## rgray (Jun 27, 2019)

Edited...I was confused for a second. Happens from time to time.
Maybe no one saw that....I can only hope.
What's below applies.

I'm remembering more of when it happened to me. I was using a new cross slide drilling attachment I built.
Using a cordless drill chucked on the end of the shaft for power.
The cordless drill had a lot of acceleration making things worse than they should have been.


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## mikey (Jun 27, 2019)

Ken from ontario said:


> 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 .



I'm with Ken. The most likely cause is oil on the screw threads of the spindle. You need to take it apart and clean it.


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## schemer (Jun 28, 2019)

Ok, thanks guys. It makes perfect sense to me that oil or grease found its way into the threads. That said, the only way I can think that it got there is sometimes after oiling the machine and then using it, I would see small droplets of oil spinning off of the spindle (I guess) and that would be the most likely way of any oil getting near the drill chuck. I appreciate all the responses to my question. I will report back once I have it resolved (or not).
Thanks


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## schemer (Jun 28, 2019)

RJSakowski said:


> Just a wild shot but you didn't have the mill in reverse, did you?



No.


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## chips&more (Jun 28, 2019)

You could use a keyed drill chuck and be done with it!


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## schemer (Jul 2, 2019)

chips&more said:


> You could use a keyed drill chuck and be done with it!


 I could but once you go keyless, you never go back!


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## schemer (Jul 2, 2019)

Ok, so I put on a new Chinese keyless chuck and it works perfectly fine. That was after cleaning the old ROHM chuck without taking it apart and hoping for the best. But today I said I am going to take that chuck apart and if I tear it up, who cares it doesn't work anyway.  So I see there is no screw on a split collar so I figure its a press fit. I make a clamp with a piece of 2x4 and clamp it in the vise and knock out the rest of the chuck and remove the cover. Underneath the cover is a 2 sided bolt (I assume) so I clamp the other part of the vise (mower cover) and get out my 24" crescent wrench to expose the jaws. I prepare for bearings to fly all over the place but there were none. Then I marked and removed the 3 jaws. All I could see was a threaded rod with a spring, a thin spacer-washer, and a flat cap where the bottom of the drill bit would touch. I figured I had to remove that 2 sided plug but they must use special tools to clamp the body and I did try to chuck it in my lathe and use that bug crescent wrench, but it didn't work. So I reassembled it and may test it another day, but it feels like it did before I started and there wasn't any grease or oil inside. I think maybe from using the same size drill bit most of the time, I may have wore the threads on the threaded rod. I guess I could see about making an emergency collet for a #3 drill for the future but I really don't think my seldom used ROHM chuch should have failed with such minimal usage.
  I did buy another same model ROHM for a spare but I am thinking of returning it and looking for an Albrecht.


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## Bob Korves (Jul 2, 2019)

The outer shell is in two pieces, which separate next to the knurling.  Look closely to find the joint there.  You will need to make a split plate to clamp on the smooth cylinder between the two knurling sections to stop it from turning in a vise.  Then you need another clamp to grip on the wider shell knurling.  Right hand thread, but often/usually/always takes a lot of torque to break it free.  With luck, you might be able to loosen it with two strap wrenches, but I wish you better luck than I have had.  Watch our for losing the bearings when it comes apart!  The Rohm chuck is similar to an Albrecht chuck to work on.  Here is an EXCELLENT step by step disassemble, clean, lube, reassemble tutorial article written by 'Mikey' here on Hobby Machinist on rebuilding an Albrecht chuck, though posted on another site many years ago.  It is better than the instructions from Albrecht and others.


			Rebuilding an Albrecht Drill Chuck – MachinistBlog.com


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## schemer (Jul 3, 2019)

Bob Korves said:


> The outer shell is in two pieces, which separate next to the knurling.  Look closely to find the joint there.  You will need to make a split plate to clamp on the smooth cylinder between the two knurling sections to stop it from turning in a vise.  Then you need another clamp to grip on the wider shell knurling.  Right hand thread, but often/usually/always takes a lot of torque to break it free.  With luck, you might be able to loosen it with two strap wrenches, but I wish you better luck than I have had.  Watch our for losing the bearings when it comes apart!  The Rohm chuck is similar to an Albrecht chuck to work on.  Here is an EXCELLENT step by step disassemble, clean, lube, reassemble tutorial article written by 'Mikey' here on Hobby Machinist on rebuilding an Albrecht chuck, though posted on another site many years ago.  It is better than the instructions from Albrecht and others.
> 
> 
> Rebuilding an Albrecht Drill Chuck – MachinistBlog.com



Thanks Bob. I had made some split plates from a 2x4 and was able to disassemble it all except the 2 final parts that expose the bearings. Rohm uses a thin 2 sided part that is easily ruined as the piece you need to put a special wrench on. When I feel like trying again I will take pics. Thanks for the link to the article.


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## schemer (Jul 5, 2019)

Ok, so I gave it another go and used my same "special tools" I made from a 2x4. The problem I had last time was they use a thin 2-sided head for you to put a wrench on. I used my large crescent wrench as I didn't have (or didn't think I had) an opened end wrench wide enough to fit. The crescent wrench slipped of and messed up the flat on one side of the part. So I gave up. This time however, I put the 2-sided flats in the vise and used a channel locks to successfully get it unscrewed. There are 23 small ball bearings in there and they are oily. I will clean it all up and dress up any scars I made and see if it works. If it does, great. It will be my spare chuck. I purchased a Techniks 82153 | 13S JT6 Keyless Jacobs Taper Drill Chuck (made in Taiwan) for my replacement. TIR @ 0.0008 so that is good enough for me. I may take a few pics and post them later...


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