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

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. :oops: 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.
 
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.
 
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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.
Click to expand...

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.
 
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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