Jacobs Rubber Flex collet chuck help

I have a Jacobs #91 Rubber Flex collet chuck with D1-6 back plate. Works great Butt!! During use it works OK, work diameter is small and in current work being turned it's 5/8" so spindle speed is high though 1000 RPM is machine limit. Also does the same on other lathes. As I mention all works great until I stop the machine, lathes all have clutch/brake control so they are not motor switched on/off. Often when putting the clutch in neutral the locking wheel will reverse and unscrew the collet nose cup. If I do nothing the nose cup will fall off, collet and work then falls out too. Locking ring is in but when the hammer wheel reverses due to deceleration the pin (I assume) pushed the ring off the the lock grove and loosens the collet nose.
I removed the 2 piece snap ring, pin dropped in the chips so I'm cleaning the lathe to find it. Lock ring fits well, all detente buttons are in and springs feel strong, without the pin that in the chips the ring seems to fit snug in the locked position, lock groove edge is square with no sign of wear. All holes for the lock pin are round with no sign of wear and before the pin dropped it too looked in good shape.
Any Ideas as to why I'm having problems? To correct the problem?

Get a Rubberflex collet chuck #92.
There are a couple on the auction site which give you the general idea:
Jacobs model 92 Rubberflex lathe chuck | eBay
Jacobs Model 92 Lever Operated Rubberflex Lathe Chuck w/ Case | eBay
I have one in A6.

I prefer the #91 like I have. Is the problem I'm having typical of the #91?

I have no explanation. My #91 only messes up when I mess up, and forget to push in the lock ring. I use mine on a Monarch 10EE, and the acceleration and braking are strong. Are your lock ring detent springs weak?

Springs feel strong though I don't know what the pressure should be. I'll be sifting thru my chips to find the pin today. I did notice pin fits kinda loose on the locking ring. Holes look great, chuck hasn't been used much, might have been a year since I previously used it. It kinda an item that comes in handy from time to time so I have it for that purpose.

rklopp said:

I have no explanation. My #91 only messes up when I mess up, and forget to push in the lock ring. I use mine on a Monarch 10EE, and the acceleration and braking are strong.

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Same experience here- never an issue as long as the ring gets closed properly.
It's important that the full diameter of the lock ring seats flat against the face- easy to kind of "half cock" it closed- in which case it will open on braking.
Hopefully it's just something that simple, otherwise sounds like something is broken or missing.

Yes I admit a few times it was my fault, I failed to push in the locking ring. So when it happens the next start-up I make sure I push in the locking ring. Not every time does the cup unscrew, the ring will pop out but not all the way so that there is enough to stop the hammer wheel from rotating. But is is noticeably quite a bit out and very near completely out. I think it might be the pin is too small in diameter but when inspecting it prior to it falling into the chips it seemed to be completely black and not worn. I seen it drop, looked very carefully at the top of the chips without disturbing them but couldn't find it so I'm collecting all the chips and will as I always do check for non chip items.

Froneck said:

Yes I admit a few times it was my fault, I failed to push in the locking ring. So when it happens the next start-up I make sure I push in the locking ring. Not every time does the cup unscrew, the ring will pop out but not all the way so that there is enough to stop the hammer wheel from rotating. But is is noticeably quite a bit out and very near completely out. I think it might be the pin is too small in diameter but when inspecting it prior to it falling into the chips it seemed to be completely black and not worn. I seen it drop, looked very carefully at the top of the chips without disturbing them but couldn't find it so I'm collecting all the chips and will as I always do check for non chip items.

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Hem's sake, Frank? You are a bright guy. Drop a coupla bucks on one of these, brown Kraft paper, or white "butcher" paper for your place:

ULINE - Shipping Boxes, Shipping Supplies, Packaging Materials, Packing Supplies

Next time you got to take sumthin' apart? ANYWHERE.. not just overtop a freakin' pile of CHIPS...lay down a clean sheet of paper.

Next time you need to grind on a lathe? First sheet oil-shot. Top sheet water soaked. Grit cleanup is easier.

Some of the water leaks? BFD. Sort that at day's end and it won't really matter. Cast-Iron ain't sugar. Grit gets under the carriage or such? That WILL matter.

CLOTH or PLASTIC catches anything spinning? We gets f**ked. Sometimes rather badly.

Paper catches? It just tears.. BFD. There's more on the roll.

Cleaned my chip pan and sorted the chips found the pin and a Hex wrench that must have fallen quite a while ago. (that's why I always check the chips before dumping them in the scarp barrel) Noticed the pin's undercut is wider than the slot by about 3/32". Also noticed the aluminum hand wheel exceeded the steel portion by about 1/32". so I faced it flush with the steel portion. I made another pin so it fit snug in the lock ring and trimmed it so it would just clear the plate with the locking holes when the lock ring was in the unlock position. I gained over 3/16" of pin in the locking hole. Removing the aluminum also allowed the detente balls to fit better in the detente groove. Assembled the unit and it works Great!1 Stays locked even when braking for quick stop.
Thanks for the help, knowing others have the same unit that works as it supposed to pointed me in the right direction.

Froneck said:

Cleaned my chip pan and sorted the chips found the pin and a Hex wrench that must have fallen quite a while ago. (that's why I always check the chips before dumping them in the scarp barrel) Noticed the pin's undercut is wider than the slot by about 3/32". Also noticed the aluminum hand wheel exceeded the steel portion by about 1/32". so I faced it flush with the steel portion. I made another pin so it fit snug in the lock ring and trimmed it so it would just clear the plate with the locking holes when the lock ring was in the unlock position. I gained over 3/16" of pin in the locking hole. Removing the aluminum also allowed the detente balls to fit better in the detente groove. Assembled the unit and it works Great!1 Stays locked even when braking for quick stop.
Thanks for the help, knowing others have the same unit that works as it supposed to pointed me in the right direction.

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Hey, Frank? "It's PM, dammit!"

"One hand washes the other".

I have TWO of these 9XX buggers, one for the pair of D1-3 10EE, one on a Cazeneuve HBX-360 backplate. Both are OLD. One is still grubby as sin coming off a bad hangover after a weekend crawling bar loos and brothel floors!

So "guess what I am going to be doing with the information YOU just now shared?"

Got it in ONE, didn' yah?

I did say "PM"?

Thank YOU!... one and ALL.



Bill

I didn't know others were having problems with the Jacobs #91. I would have provided photos. When I found the pin I put it in the hole without the locking ring, It went approx .20 beyond where the ring would allow it to enter so the locking holes are deeper than needed. Before facing the Aluminum Hammer wheel I measured the dept of the far edge of the detente balls in the locking ring. I compared that to the distance the outer edge of the detente grove. I didn't want to exceed that and machined to slightly less so that the detente balls force the locking ring against the hammer wheel. I trimmer the aluminum and some of the steel to allow maximum locking pin length. I then made the pin (.3125 diameter)at least 1/4" longer. The locking ring has a .250 slot with full radius bottom with wider .3125 "counter slot" that the grove cut into the locking pin fits into. (Slot in the ring was probably made by 1/4" end mill then 5/16" end mill so 1/4" is about .200 long) I made the pin from 1/2 hard 4140 I just happen to have. I did have 3/8 and 1/4" dowel pins but no 5/16" so I used the next best thing.
I trimmed pin length with locking ring located by eye until near desired length then used 1/2 of the 2 piece snap ring (easier to remove and replace) until pin was ideal length. Assembled with both halves of the snap ring and it work's as I assume it should!

Froneck said:

I trimmed pin length with locking ring located by eye until near desired length then used 1/2 of the 2 piece snap ring (easier to remove and replace) until pin was ideal length. Assembled with both halves of the snap ring and it work's as I assume it should!

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Just a guess, but .. many of these are in the hands of second and subsequent owner's. maybe a lot more than just two!

Some have been allowed to corrode. Some earn attempted DIY repairs.

Guess which ones are most likely to have an "issue".. then end up on eBay.. and become the very ones we in-need first get our hands on?

Got it in one. The messed-up ones.

I don't think the lathe trimming was needed at all.

But the right fit to the pin?

Dambetcha!

when I disassembled my #91 I could not find any reason for it to self unlock. I have made sure it was locked many times after having to stop it from completely unscrewing from the cup. Pin was black in color probably from heat treatment. No sign of wear! Holes were round and not worn. Measuring the location of the detente balls and the grove it just went slightly past the ball center-line. Now that I trimmed the surface of the hammer wheel the balls provide a stronger force on the pin and require a bit more force to pull out the pin. One I have came with a Govt. Surplus lathe, if it was used it wasn't used much! There are no indications anyone attempted repair. Prior to my trimming pushing in the locking ring resulted in it just sliding toward the hammer wheel, now if it is about 1/32" away the detente balls pull it closed. I suppose making the pin longer helped too but there is a limited amount of movement of the ring so pin length is limited to the amount the ring can move so trimming added to the pin length limit.

Froneck said:

when I disassembled my #91 I could not find any reason for it to self unlock. I have made sure it was locked many times after having to stop it from completely unscrewing from the cup. Pin was black in color probably from heat treatment. No sign of wear! Holes were round and not worn. Measuring the location of the detente balls and the grove it just went slightly past the ball center-line. Now that I trimmed the surface of the hammer wheel the balls provide a stronger force on the pin and require a bit more force to pull out the pin. One I have came with a Govt. Surplus lathe, if it was used it wasn't used much! There are no indications anyone attempted repair. Prior to my trimming pushing in the locking ring resulted in it just sliding toward the hammer wheel, now if it is about 1/32" away the detente balls pull it closed. I suppose making the pin longer helped too but there is a limited amount of movement of the ring so pin length is limited to the amount the ring can move so trimming added to the pin length limit.

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You are "rationalizing" over something you missed. A flaw that was "masked", if you will. I know not WHAT, but ""missed" is not a mere guess.

Jacobs didn't SHIP as many as they did for as LONG as they did to LAST as long as they have ... with an inherent design flaw of that significant an effect.

Something you were NOT looking at could have simply been burred, bent, no longer in HT specs, or just badly worn but not obvious unless you had dimensioned drawing with specs... or a genuine brand-new to compare to, side-by-side.

Good on yah for fixing it.
Good on yah for sharing.

But a lathe skim cut is not likely to be "the school solution".

Not YET , anyway!

Which reminds me .... I think I'm clear out of Kroil?



And even getting low on.. be damned.. there it is..

Yes I'm sure it wasn't shipped working the way it was! Not much to see, a simple arrangement. BUT the possibility of the springs getting weak could have caused the issue. Not sure how to remove the balls to get at the springs. Weak springs can only be the cause of the problem unless someone made a pin. If there was anything I missed it would be spring strength and I have no way of knowing what they should have been nor how to replace them. However it's working great! I'll put the pin in a pill bottle label it and place it in a draw that has other similar parts.

Froneck said:

Yes I'm sure it wasn't shipped working the way it was! Not much to see, a simple arrangement. BUT the possibility of the springs getting weak could have caused the issue. Not sure how to remove the balls to get at the springs. Weak springs can only be the cause of the problem unless someone made a pin. If there was anything I missed it would be spring strength and I have no way of knowing what they should have been nor how to replace them. However it's working great! I'll put the pin in a pill bottle label it and place it in a draw that has other similar parts.

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LOL! I recall discovering (pre-internet days) a book on the construction of US Navy Torpedoes.

Having a background in extreme high pressure air, I jumped to the conclusion from the pressure spheres that they were air-powered and remarked on it to a house guest and relative by marriage.

He acidly looked at me as if I was ten flavours of a fool.

"It works better if you use the compressed air to combust the Alcohol fuel".

... said the retired War Two Full Commander, USN.. who had been involved in design and development of the very torpedo I was looking at.



Oddly, we can probably find nore information about that once-classified torpedo today than we can about the specs of the inner workings of an ignorant Jacobs rubberflex chuck!

Oh well.

At least the Jacobs doesn't f**k up the machinery as badly if we get the timing of it wrong ..