[How-To] Jacobs Rubber Flex Collet Chuck Service 91-C6

[FliesLikeABrick]

I recently had an opportunity at an auction to pick up two Jacobs rubber flex collet chucks. After finding a great, brief Youtube video on the first few steps of disassembly as well as the attached manual, I went ahead and broke one of them down for a full clean/lube service. I went a few steps further than the author of the video, because I was keen to get the bearing race cleaned out and lubed

They both started out looking kinda like this. Everything seemed to move and work right, lock worked, etc... but the bearings were dry and I couldn't in good faith put this on the lathe and just go to work.




Disassembled


Put the parts through the ultrasonic cleaner, then the steel parts in evaporust for a few hours. Rinsed with hot water, blown dry with shop air, then hit everything with a bit of paste wax to prevent flash rusting.



Reassembled quickly and easily, the manual says a light machine oil for the ball bearings (33x 1/4" balls inserted through a small port), as well as on the threads of the nose.

Cleaned up real nice, ready for its next decade or two of service.





Before and after more or less. The second one to clean up is the dirtier one, and is the one that should fit my D1-3 spindle on the Chipmaster


The one on the left should be D1-3, but it had been screwed to an adapter plate for the previous owners' usage -- so I have some camlock studs on order for it.



Need to take some measurements and identify what spindle the clean one is meant for, and help find it a new home.



I also have a few sets of collets that appear to be complete, those cleaned up pretty easily. Ultrasonic, evaporust for a bit of surface rust, then a light oiling to help them store well.

 

[FliesLikeABrick]

I think based on the measurements, the one I cleaned up is a D1-6 -- but only with 3 camlock studs on it? The studs are 7/8 diameter which seems to only be used on the D1-6; and the widest part of the taper measures around ~4.18 wide and .718 deep which seems about right.

 

[Martin W]

Thing of beauty! Nice job!
Martin

 

[keeena]

Nice job on the refurb; looks great. I've been looking for 2yrs for a 91-C5; rare bird.

And yes - that 91-C6 is for a D1-6 spindle. They made them with only half the camlock studs.

 

[mmcmdl]

Spindle Type and Size Guide

It’s essential to know your machine spindle type and size when replacing or upsizing a lathe chuck on your machine. Use this guide to accurately measure.

www.toolmex.com

 

[pontiac428]

I think based on the measurements, the one I cleaned up is a D1-6 -- but only with 3 camlock studs on it? The studs are 7/8 diameter which seems to only be used on the D1-6; and the widest part of the taper measures around ~4.18 wide and .718 deep which seems about right.

I spotted that, but figured you knew what you were doing. Many low-load cam pin chucks have 3 pins, including the Jacobs and drive plates, etc.

I absolutely love my flex collet chuck! The extra diameter and solid, concentric holding make them better than any other collet system- they still haven't come up with Rego-fix collets for 1-1/4"-1-1/2" like Jacobs! So much self-centering. Such work holding contact. I don't think a better system exists, especially if your spindle bore is greater than the largest collet.

It looks to me like a bolt-on backplate on the second chuck you haven't cleaned yet would work for your Chipmaster.

It's funny to me that the 33 ball bearings are the easy part compared to the teeny tiny little internal circlip that holds the plug for loading the balls- that is one of the smallest internal circlips I've ever had the pleasure of modifying tools to remove. I ended up using a dental instrument that they use for isolating teeth with a dental dam for drilling root canals!

 

[FliesLikeABrick]

I spotted that, but figured you knew what you were doing. Many low-load cam pin chucks have 3 pins, including the Jacobs and drive plates, etc.

I absolutely love my flex collet chuck! The extra diameter and solid, concentric holding make them better than any other collet system- they still haven't come up with Rego-fix collets for 1-1/4"-1-1/2" like Jacobs! So much self-centering. Such work holding contact. I don't think a better system exists, especially if your spindle bore is greater than the largest collet.

It looks to me like a bolt-on backplate on the second chuck you haven't cleaned yet would work for your Chipmaster.

The second chuck actually is natively D1-3 (!) -- the previous owners had taken the camlock studs out and used those holes to bolt it to a back plate of their own for a larger lathe. I have some studs coming, hopefully this week - then I can put it to use

 

[pontiac428]

The second chuck actually is natively D1-3 (!) -- the previous owners had taken the camlock studs out and used those holes to bolt it to a back plate of their own for a larger lathe. I have some studs coming, hopefully this week - then I can put it to use

Best possible outcome!

 

[FliesLikeABrick]

I ended up making my own video to go a bit further than the one I referenced above. This post was written after I cleaned the first chuck up, then I decided to take a shot at recording and talking through the second one a bit.

 

[FliesLikeABrick]

Couldn't help myself and tested - borrowed the camlock studs from another chuck. Works great, appears to give me between .001 and .002 TIR measured approximately 2" from the collet face. Likely will be pretty reliable .001" or better as long as the workpiece, chuck, and taper is clean (and notwithstanding any damaged or worn collects).