# Jacob's Rubber Flex Collet Chuck-Lessons learned



## Janderso (May 19, 2020)

I traded for two Jacob's Rubber Flex Collet chucks a few months ago. Having no experience with them I had no expectation as to accuracy or total indicated reading of run-out.
The first time I mounted the better of the two, I placed a 1/2" to 9/16" (I think) put a piece of stock in and checked TIR. I was very disappointed to find it was in excess of .005".
I took them apart and cleaned-oiled them. I also used my precision stones (thanks Bob) to de-burr the outside of the collets. The set came with three boxes of collets including the square and hex I believe.
I checked TIR again, no better. Then I watched a Youtube video on a method of mounting the D1-6 chuck loosely and tapping like you would a 4 jaw chuck. That helped a little bit but still not very good.
Last weekend I decided to get to the bottom of this issue. I decided I would try clocking the way I mounted it and try to identify and mark the best clocked position true to accuracy. In the process, I found that when I really tightened the lugs, the TIR got much better.
Eureka! That's the trick? Tighten the lugs of the cam lock? Really tight? = YES.
I have less than .001" on every collet I tried. Each collet was cleaned and deburred.
If you have struggled with your Flex collet chuck, try it.
I hope it works for you.


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## Ed ke6bnl (May 19, 2020)

Janderso said:


> I traded for two Jacob's Rubber Flex Collet chucks a few months ago. Having no experience with them I had no expectation as to accuracy or total indicated reading of run-out.
> The first time I mounted the better of the two, I placed a 1/2" to 9/16" (I think) put a piece of stock in and checked TIR. I was very disappointed to find it was in excess of .005".
> I took them apart and cleaned-oiled them. I also used my precision stones (thanks Bob) to de-burr the outside of the collets. The set came with three boxes of collets including the square and hex I believe.
> I checked TIR again, no better. Then I watched a Youtube video on a method of mounting the D1-6 chuck loosely and tapping like you would a 4 jaw chuck. That helped a little bit but still not very good.
> ...


I have the set and seem to have extra run out BUT I have L00 mount. I do like the flex ability of the Collets. I got my chuck for $30 sold as not working parts. Helps if you pull the ring out to mount the Collets.


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## ErichKeane (May 19, 2020)

Ed ke6bnl said:


> I have the set and seem to have extra run out BUT I have L00 mount. I do like the flex ability of the Collets. I got my chuck for $30 sold as not working parts. Helps if you pull the ring out to mount the Collets.



I have an L1 mount and find that my TIR is measured in the low-end of tenths.  I would expect L-series mounts are much more repeatable due to the taper.

I DID find when I got mine that I had to adjust the backing plate connection to match my lathe, but my runout is basically non-existent.


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## Ed ke6bnl (May 19, 2020)

I will have to see if there is some adjustment in the back p look plate, thought it was inteagal to the chuck


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## Janderso (May 19, 2020)

Thinking about having to really pull the chuck into the tapered register makes me think the fit is tight, that's a good thing right?
I always make sure to run my hand through both mating surfaces to watch for chips/debris.


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## Shootymacshootface (May 19, 2020)

I got a Jacobs spindles nose collet chuck with my lathe, but it had no backplate. I bought a semi-finished backplate with an l00 mount and cut it to fit the chuck. I also have basically 0 runout. I think that cutting it on the lathe had a lot to do with that. I really that chuck.
The only bad thing that I have heard about the Jacobs sncc is that if you take very heavy cuts, the metal fingers in the collet can lay over. I don't think that I could ever push things that hard with my 1hp Clausing.


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## Janderso (May 19, 2020)

Yeah, I can see a potential problem with taking an aggressive cut. Unless the steel fingers were touching metal to metal (bottomed out) there has to be some lateral flex.
It's a quick way of holding cylindrical parts that should be able to repeat. I haven't tried yet.


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## Shootymacshootface (May 19, 2020)

Yes, extremely repeatable. I read somewhere that the reason that it was discontinued was because of the price point, around $6000 in todays dollhairs.


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## Ulma Doctor (May 19, 2020)

The manual mentions that multiple impacts from the tightening ring insures the grip on the part.
I have suspicions that the TIR is reduced as well when the collet is fully seated


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## Janderso (May 19, 2020)

Ulma Doctor said:


> The manual mentions that multiple impacts from the tightening ring insures the grip on the part.
> I have suspicions that the TIR is reduced as well when the collet is fully seated


I haven’t read any manual, good to know.
Thanks Mike.


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## mmcmdl (May 20, 2020)

I had a D1-8 mount , LOO and I now have an L0 mount Jacobs with a couple full sets of collets . I used them all with good success over the years . I unfortunately sold the L00 and D1-8 and am left with only the L0 . I need an L00 mount Jacobs for the Clausing lathe I own now . If anyone has an L00 and needs an LO mount , I'm definitely in for a trade . 

Yes , these chucks were very expensive back in the old days . 

Along these same lines , this past week we removed a metering pump for one of our extruders in at work and disassembled it for a major cleaning as it was packed with carbon . It very much reminded me of the Jacobs internals . This pump was $20 grand to replace so I could see why the Jacobs would be expensive . I'm going to install this pump back on the line today so hopefully we get some good results . #2 finishes and flat to 7 light band specs all over this thing .


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## Shootymacshootface (May 20, 2020)

Dave, you can get an 6 1/2" l00 back plate from CME for, I think they are $68. Then just cut to fit. I have bought 2 from them the tapers fit perfectly.


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## matthewsx (Feb 17, 2021)

I bought one of these chucks with a 2" 8 tpi backing plate.









						What Did You Buy Today?
					

Did you have to pay duty on the hobby metal aluminum coming into Canada?   I can't know because I paid duty for everything in a single box from parcel forwarder.




					www.hobby-machinist.com
				




Any chance they ever made a DIN 55027 spindle mount, or an A1-5 A5 backplate that I could look for? Is there such a thing as an A5 to A6 adapter? I have some backplates that I'm trying to make work once I get my gap back and installed









						Backplate Improvisation
					

So, my 13x40 Bolton lathe has an unusual DIN 55027 spindle mounting that took me a while to figure out what it was. They seem to be more common in Germany or maybe even Russia but pretty much rare as hen's teeth here in the states. I did get a quote on a Rohm part but it was over $600 for one...




					www.hobby-machinist.com
				




I actually drilled and tapped one for the lugs rather than the kludge in my post but It seems like I'll need to fill in the holes, then cut a 4" taper into the front of my backing plate.

Sounds like it would be worth the effort from what I read in this post but would be much easier with something closer to what I need.

John


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## matthewsx (Feb 17, 2021)

Or, would it make more sense to sell this one and buy a cheap ER collet chuck. We are talking about a Bolton lathe here after all....

John


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## Shootymacshootface (Feb 17, 2021)

The backplate on thoseis removable, it doesn't matter what model it is. Just get a backplate to fit your machine and cut to fit.
Awesome chucks!


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## Ed ke6bnl (Feb 17, 2021)

I had a Jacob flex with D1-4 non removable back plate (darn) I got a backplate for L00 and unscrewed the D1-4 mount studs and with adaptor used those mounting holes for the Loo back plate to the jacobs chuck. I do like that chuck and use it all the time.


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## matthewsx (Feb 17, 2021)

Shootymacshootface said:


> The backplate on thoseis removable, it doesn't matter what model it is. Just get a backplate to fit your machine and cut to fit.
> Awesome chucks!


I have some backplates that I'm making work for this machine (the real ones DIN 55027 are ~$600 and have to be special ordered from Europe). The challenge will be cutting the taper with the existing holes in the A5 backplates I have. Instinct tells me I should fill those holes in before cutting but how is the question.

John


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## Shootymacshootface (Feb 17, 2021)

Ouch, those are expensive backplates!


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## ErichKeane (Feb 17, 2021)

Yeah, what is up with that design that makes them so expensive?  I understand something like an L1 being expensive, but that looks like a pretty simple plate with a taper on it.


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## mmcmdl (Feb 17, 2021)

Never really looked to see if the back plates were removable before this . If they are , I could've saved myself $300 bucks on an L00 .


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## Shootymacshootface (Feb 17, 2021)

Yes, I seem to remember taking a giant retaining ring off of the front of mine to remove the hammer ring. The bolt heads are under there.


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## mmcmdl (Feb 17, 2021)

Too late now , I already bought an L00 chuck , but I'll take a look right now for future reference . Maybe someone on here needs one . 


Shootymacshootface said:


> Yes, I seem to remember taking a giant retaining ring off of the front of mine to remove the hammer ring. The bolt heads are under there.


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## Illinoyance (Feb 17, 2021)

Remember, if your work does not extend through the collet you need to support the back end of the collet.  Jacobs supplied a rubber plug for that purpose.  ER collets need support on the back end if the work does not go all the way through.


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## Illinoyance (Feb 17, 2021)

Be careful with that hammer ring.  You can squash thin walled parts.


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## mmcmdl (Feb 17, 2021)

Yes sir , retaining ring is located behind the nosepiece , maybe I'll split the L0 tomorrow during the snow storm .


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## matthewsx (Feb 18, 2021)

So, consensus is hold onto it and make it work with whatever lathe you have?


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## Shootymacshootface (Feb 18, 2021)

matthewsx said:


> So, consensus is hold onto it and make it work with whatever lathe you have?


I believe tbat is what Jacobs did, and then assign different model #'s to the same chucks with different backplates.


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## matthewsx (Feb 18, 2021)

Shootymacshootface said:


> I believe tbat is what Jacobs did, and then assign different model #'s to the same chucks with different backplates.


I think the A6 refers to the taper on the chuck body, if it were an A5 it might bolt right up to my spindle. As it stands I have these A1-5 A5 Rapidhold backplates that have the right taper and hole spacing for my DIN 55027 spindle.




Stock 3 jaw on the right, backing plate on the left.




Holes that I think I need to plug to avoid an interrupted cut.




I do have some time to figure it out since another member here @Cooter Brown  has the gap piece for my lathe (which he's kindly repairing for me) and I think I'll need it to get close enough to make a good cut on the backplate. 




I know it's really improvising but when I finally figured out what the spindle on this lathe is I contacted Rohm who referred me to a dealer here in the bay area and I got a quote on the right backplate. Yes, it was over $600 and had to be shipped from Europe. They do show up on eBay in Germany for some reason (maybe it's a Russian spec) but communicating with sellers and getting them to ship to California is pretty tough.

If I can get my 4 jaw mounted I might be able to modify the backing plate that came with it but I'm worried about stacking errors becoming a problem.




John


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## Shootymacshootface (Feb 18, 2021)

matthewsx said:


> I think the A6 refers to the taper on the chuck body, if it were an A5 it might bolt right up to my spindle. As it stands I have these A1-5 A5 Rapidhold backplates that have the right taper and hole spacing for my DIN 55027 spindle.
> 
> View attachment 356030
> 
> ...



I'm sure that you already searched Google and eBay,  right? I have mentioned before that my go to for chucks and backplates is CME.
What chuck or chucks do you have fitted to your lathe right now?


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## matthewsx (Feb 18, 2021)

Yep, I check pretty regular to see if anything pops up that I can use, I suppose I should set some kind of alert but I doubt there's anyone else looking for them or somebody in China would list them. I'm pretty sure a Chinese supplier could get their hands on one but that would make dealing with Germany look easy.

All I have right now is the stock 3 jaw chuck that came with the machine. I had one place in Georgia offer a stock 4 jaw but I had no way of making sure it was the right part and I was looking at freight for that and a bunch of other stuff I no longer need.

I checked out CME right after you posted it on this thread, good stuff there....


John


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## Choiliefan (Feb 19, 2021)

I have two A6 Jacobs collet chucks.  Both have integral mounts so no adjustments possible.
My smaller 500-series chuck (1") capacity has a removable backplate so it can be fine-tuned to a couple tenths TIR.


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## Shootymacshootface (Feb 19, 2021)

matthewsx said:


> Yep, I check pretty regular to see if anything pops up that I can use, I suppose I should set some kind of alert but I doubt there's anyone else looking for them or somebody in China would list them. I'm pretty sure a Chinese supplier could get their hands on one but that would make dealing with Germany look easy.
> 
> All I have right now is the stock 3 jaw chuck that came with the machine. I had one place in Georgia offer a stock 4 jaw but I had no way of making sure it was the right part and I was looking at freight for that and a bunch of other stuff I no longer need.
> 
> ...



If I were you I would use your 4 jaw independent chuck and put the back plate from the 3 jaw on it, then patiently search for 2 more backplates. 
I would consider a 4 jaw a necessity, and the collet chuck and 3 jaw niceties.


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## matthewsx (Feb 19, 2021)

I agree on the necessity of the 4 jaw, honestly I'm thrilled with the Bison I got yesterday, it looks like it's never been used.

Unfortunately my 3 jaw has an integral backplate, I figured out that a "C" mount size 5 is the same taper and bought 3 backplates for $100/ea a while back with the intention of modifying them to  work on my machine.

Here's one of them.



and here's another one mounted on the lathe.



I think Bison sells one specifically for my spindle and will check with a dealer to get pricing and availability but my hopes aren't high for it being less than twice what I paid for the 4 jaw and Jacobs chucks combined.








__





						Bison
					






					www.bison-america.com
				




John


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## Shootymacshootface (Feb 19, 2021)

Maybe you could just buy 1, and then duplicate it. Thats how China got where they are today!


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## matthewsx (Feb 19, 2021)

Shootymacshootface said:


> Maybe you could just buy 1, and then duplicate it. Thats how China got where they are today!


I have 3 of the ones pictured that fit the spindle, if I can use those rather than spend another $600 I'll do that.


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## Shootymacshootface (Feb 19, 2021)

matthewsx said:


> I have 3 of the ones pictured that fit the spindle, if I can use those rather than spend another $600 I'll do that.


Ah, lost track.


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## matthewsx (Feb 20, 2021)

I figured out how to cut my backplate. My dad left me this huge chunk of steel which should be more than rigid enough when bolted to my cross slide to bridge the gap and get me up close to the backplate. Just need to drill a few holes and attach the toolpost but if I can get the 4 jaw mounted I should be able to get the the Jacobs mounted too.




John


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## Shootymacshootface (Feb 20, 2021)

Here's what mine looks like. If you were to look up the model #, it is supposed to have a different backplate on it. Also, notice that it bolts on from the inside. It registers on a shoulder cut into the backplate.


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## matthewsx (Feb 20, 2021)

Mine is the same except the backplate has an internal 2" x 8 tpi thread. Same numbers on the actual chuck body.


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## Choiliefan (Feb 21, 2021)

^^ It appears an L-series backplate has been adapted to fit an integral body A6 chuck.
I may try this if/when I get my LOO Clausing project lathe going.


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