A story about Bison & Fuerda (Gator) chucks ...

My 8" Bison forged steel Set-Tru chuck has had a weak grip since day 1 (bought almost 3 years ago). Slippage in the jaws has messed up a part or three but it finally scarred a customers barrel & that meant polishing, bead blasting & blueing - about a $100 net loss on that job. I talked with Bison customer service right after purchasing the chuck & they indicated that the very smooth grind necessary for small T.I.R. was causing the problem - like a dummy I believed that story until this week.

I spoke with a number of chuck manufacturers & importers & all said the same thing ... the top jaws are not correctly ground. Phoned Bison CS again & explained the situation, they said after 12 months they would do nothing except sell me another set of top jaws for $237.80 + shipping & wouldn't guarantee that those would be any better. That seemed wrong so another call was placed, this time to the manager of CS. She said exactly the same thing & added that the next time I had a problem it needed to be addressed during the 12 month warranty. I told her that I'd never have a problem again with anything Bison since I'll never buy that brand again. Her reply is classic ...

Sorry about that.

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I told her a few things that cannot be printed on a family forum, questioned her skills & abilities & suggested that she change her job title to Customer Service Avoidance Manager ... & hung up disappointed.

Seemed like there are four options, all somewhat expensive.

1) Sell the Bison on eBay for half of what it cost & buy a Kalamazoo Micro-Set or similar. About $700 difference.

2) Buy the Bison top jaws & hope they are better. $250 there & iffy.

3) Find a chuck grinding shop, ship off the entire chuck with jaws, wait a month & be guaranteed a good result for $800 (Worldwide Chuck Services does this & probably others)

4) Bore the jaws myself ...

The issue on in-shop boring is that the jaws must be pre-loaded & that means purchasing some type of boring ring. Dorian makes a really nice one for $899 & Ajax Tools sells an almost identical copy for $350 + $15 shipping. Called my old buddy Rocky at Ajax & managed to get the boring ring for $299 + $15 shipping. He said not to tell anyone except my friends on PM (Call Toll Free (800)-543-5998. Monday - Friday 8-5 & be sure to speak only with Rocky).

The fixture is made by Taiki Industrial in Taichung City, Taiwan. Jaw Boring Fixtures (3 - Jaws)(TL-125) - Taiki Industrial Co., Ltd.

Nicely done (should be for three Franklins) and works well. Can't imagine that the Dorian version is any nicer. BUT ... all rings are made to fit flat soft jaw & won't work on step jaws unless the step jaws are modified. First step was to plunge bore the jaw bolt hole opening to .750". The jaws are over 65 HRc & the speed was set to 150 rpm to produce a surface speed of 29 sfpm. First tool was a radius edge solid carbide 4-flute mill followed by a square edge solid carbide 4-flute mill.



The factory bore (on the bottom) is rough but the new bore came out really smooth.

Then turn down the bolt heads to .500" to fit the .500" hole in the adapter, press the head into the adapter & silver braze.



The adapters come out even with the face of the jaw & allow the fixture to grip:







Chucked up the 1.5" Thomson shaft & immediately noticed that the wrench went tight. Before it would go sort of tight, then the next pinion would tighten a bit more, then the next pinion, etc. Now any pinion brings the jaws closed & that's it. TIR after boring read .0004" without any adjustment of the Set-Tru screws. After grinding the TIR should be .0002" or less.

Time spent cleaning & greasing the chuck - 3 hours. Time to plunge mill the jaws & machine the adapters - 7 hours. Value of a chuck that grips as it should ... priceless

Ordering the small 1" diameter with 1/4" bore Norton stones from Sopko tomorrow & should have this done soon.

Here's the interesting part of all this & why the title mentions Fuerda-Gator. Andrew Latawiec (previously in charge at Bison) is now VP at Global Tooling Solutions, maker of Gator (the new name for Fuerda) chucks. I'd spoken with Andrew some years ago, easy to remember his heavy Polish accent & he's really happy to be away from Bison because of "a number of changes that were taking place". Related my lack of customer service story & he assured me that will not happen with Gator & GTS as long as he's in charge.

The Gator chucks are 100% dimensionally identical to Bison (wonder where Andrew got those prints ???) so a Gator chuck will fit a Bison backplate, etc. Global Tooling Solutions has these made in China & has in the factory QC by GTS employees. Probably the only shop in China full of Eastern Europeans with a heavy Polish accent. Chucks are checked again when they reach the USA & all carry a 2 year warranty.

Will I ever again buy anything Bison - right after Hell freezes over. The closest competitor is Kalamazoo (KCM) still made in the USA. Nice folks on the phone & I've not heard anything negative about them. The Fuerda-Gator gets good reviews from people I trust - nothing wrong with a Polish designed product, made in China & back by USA sales & service.

I'm confused

Just what is the form error these "defective" top jaws exibit? And what remediation have you performed in these modifications?

I do know that when the jaw contact surfaces closely match the workpiece, drive and security is at it's highest. That's why machinable top jaws are so useful! (to me at least). I have a set of "Jaw stops" that look like three lobe nija throwing stars ;-) 'Seems to work for me.

Unless there is taper or bell mouth in the jaws "out to in" such as so often seen with years worn jaw chucks . In that case, I like the "close down lightly on a stationary lapping bar" touch up method.



At times, I've been seen putting the smallest dab of clover compound in the jaw contact pad when preparing a delicate workpiece that won't be spinning too fast. (alu. rings in example) Purist will real back in horror, but these machines are gonna out live me anyway ;-)

Cheers

Cal

I have a 6" Gator set true that has been excellent for about a year so far, I'm very happy with it.

CalG said:

Just what is the form error these "defective" top jaws exibit?

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I don't know.

And what remediation have you performed in these modifications?

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They grip as they should have the entire time.

Seems quite subjective.

An unknown quality that when changed in an unknown way results in performance that meets your expectations?
I can imagine that the jaws of a chuck could be formed in a defective manner, but I would also think that such a defect could be noticed. (and remedied by the usual methods, of which there are many that could be less costly than $300)

I sympathise with your anguish however.

The chuck would hold a 1" OD 6061-T6 rod when being drilled with a 3/4" twist drill. It wouldn't hold a 1" OD 4140HT rod when drilling with the same sized drill or smaller, even a 1/4" twist drill pushed the stock back into the chuck.

Using the tailstock to support work was always a gamble. Almost any roughing cut would move the work into the chuck an off the center in the tailstock.

Seems quite subjective.

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Totally.

An unknown quality that when changed in an unknown way results in performance that meets your expectations?

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I spoke with both manufacturers & chuck repair shops & all said the same thing - the jaw contact isn't correct. All suggested grinding out the jaws to correct the problem. Didn't have a 1" wheel for the Dumore (will order that today) but the 1-1/4" boring bar restored enough contact that the chuck can be used until the jaws are ground, which may be a week away.

... there are many that could be less costly than $300

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Seems like all the boring rings ran $200-$300. The traditional set with 40-50 rings ($300), the plate style ($200), etc. Could have made a single diameter ring on the mill but the step jaws had to be modified no matter what type or style of ring was used.

The $300 for the adjustable ring is a fraction of the total repair cost. Here's a break down:

Half a day (4 hours) on the phone with manufacturers & repair shops $300
Almost a full day (7 hours) milling out the jaw pockets, machining the adapters & boring the jaws $525
An hour on the web looking for a 1" wheel with a .250" bore & 1/4" thickness $75 + around $20 for the wheel
About $900 in billable shop time without counting the $300 for the adjustable ring

I'd like to think that Andrew Latawiec would have handled this differently had he still been at Bison - he was always very helpful in the past. And my "go to" customer service rep (also named Andy) always fixed problems but he left a year ago, cannot imagine why. But I learned more about chuck jaws than I ever wanted to know, corrected a problem that's bothered me for almost 3 years, and have a good idea that if this chuck is ever replaced it will be with either a Kalamazoo (about $1400) or a Gator (about $850).

thermite said:

Puzzles me that THEY could make that determination based on a conversation, chuck not even in their eyesight, while YOU who did have hands-on could not only have proved/disproved it as cause, but actually measured 'by how much' and in which direction.

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OK, I admit I slept through Chuck Jaw Measuring 101 & haven't a clue how to measure 'by how much' or in which direction. I'm eagerly awaiting detailed instructions on this procedure.

Six jaw chucks are primarily made for gripping tubing and other materials where deformation from a three jaw chuck might be problematical. They do not provide as much clamping power as a three jaw. For most purposes, they are OK to use, but cannot be depended on for heavy cuts. I would not recommend using one for a critical job where slippage might be a problem, ie threading a barrel tenon.

precision tools said:

Six jaw chucks are primarily made for gripping tubing and other materials where deformation from a three jaw chuck might be problematical. They do not provide as much clamping power as a three jaw.

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That's the reason the chuck in question is a 3-jaw.

When I think of a scroll chuck that won't hold the work, I first think of the condition called "bell Mouth". That is, the clamping surface away from the chuck body( the top jaw tip or toe) is "open" compared to that portion of the jaw nearest the chuck body. This condition is frequently encountered on old and used chucks, chucks that have seen "abusive" tightening of discs or rings at the very outer most portions of the jaws, or MOST likely chuck jaws that have had work pieces Snatched out of thier grasp and flung about the shop due to too great an overhanging length, tool but hogging under, or other "crashes", i.e. just about any other failure to support the work.

The first situatioin results in WEAR, and can be seen as a broadening of the jaw contact surface and can easily be witnessed by clamping up a true round bar snugly but not over tight. (over 25 mm diameter helps) Looking for light between the jaw and the work tells all. If there is only good contact at the heel of the jaw, you haven't got much going for you.

The second and third situations result in DISTORTION< bending the jaws. Either at the bolting on surface or just in the jaw projections themselves. Testing for the "Bent body" follows the same test as for wear, and can also be as simple as placing two jaws back to back or face to face while being referenced to a flat surface (surface plates are good) The jaws should form a perfect right angle with any light showing at the tips suggesting trouble. (Think of testing squares)

A black out fit is expected when new, crowding at the tips, loose at the heels might be even better!

Now since your results have ended to your satisfaction, we can assume that the part of your two piece jaws that reside in the chuck body and come into action with the scroll are in good shape. Me, I would back them out (even though you just throughly cleaned your chuck) and test them on a surface plate as well. Any "gaps" between the two jaw parts under light clamping is a problem shown.

Now reworking jaws will correct a host of ills, but it can not restore true flat or square. These are things to be evaluated and considered. I have known of times where it was good practice to slightly UNDERCUT the jaw contact surfaces to accomodate wear in the jaw guide surfaces and assure that the jaw TIPS came to bear "just" prior to the jaw heel.

A carefull inspection of the chuck body guide ways usually will detect the distortion due to a bad crash. With one of the channels showing a ding where the jaw had been wreched mercilessly. That is a CAREFULL examination. Slide the free master jaws in and out while the chuck face is separated from the scroll. (look to that scroll too!)

On work where surfaces matter, I like to interpose a slip of brass or aluminum stock between each top jaw contact land and the work piece. The soft metal acts as a compliant element both conforming to and prtecting the important workpiece that is being restrained. (DONT USE PLASTIC, too slippery!) Same methode for fitting up "imperfect" stock to bring it into acceptable run out. (It certainly can't be MY chuck showing .020 out ;-))

Getting careful work set in a jaw chuck securely without damage or distortion is something gained by throwing a few work pieces around the shop, and leaving jaw marks on others. I prefer any sort of collet, even if only a split sleeve to place between the jaws and the work.

I hope this helps.

I hate it when things are going bad, and I don't have a clue why.

Facts! We need Facts ;-)
\

Cheers

Cal

Possibly compare the parallelism between the jaw's ID faces and the groove that rides in the chuck body?

Looks to me like the jaws were bored on a fairly small diameter from the factory. Now the clamping surface area at the business end is larger post-re-boring. BUT!- unless the OP is doing all his work at the diameter at which he bored or smaller, only the edges are making contact, and are freshly 'sharpened' and are biting in. Perhaps having the biting surface along the spindle axis spread out radially is what has cured the problem.

Cal,

I really appreciate the detailed explanation. You discuss points never mentioned by any of the chuck makers & rebuilders I spoke with.

The 3-jaw forged Set-Tru has seen not much use because of the weak grip. Normally ran either the 10" 4-jaw or the Set-Tru 5C collet chuck. The 3-jaw is like new because it's hardly ever been used, never been crashed by a tool holder or boring bar, etc. The backs of the master jaws, jaw ways & scroll plate look like new. When it was apart the insides were pretty clean but I scrubbed out all the original grease & repacked with fresh Fuchs (Bison) chuck grease. No mechanical defects were noted. Before the jaws were bored they looked perfect.

I have known of times where it was good practice to slightly UNDERCUT the jaw contact surfaces to accommodate wear in the jaw guide surfaces and assure that the jaw TIPS came to bear "just" prior to the jaw heel.

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The person at Kalamazoo said much the same thing, that jaws are factory ground on a very slight taper so the outside tips touched first. Couldn't figure out what angle to set the taper attachment to, have to think it's pretty small as in a few minutes of angle.

precisionworks said:

Cal,
The person at Kalamazoo said much the same thing, that jaws are factory ground on a very slight taper so the outside tips touched first. Couldn't figure out what angle to set the taper attachment to, have to think it's pretty small as in a few minutes of angle.

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It could probably be determined after measuring the running clearances of the chuck and using some trig, if one were interested.

Screwmachine said:

Looks to me like the jaws were bored on a fairly small diameter from the factory. Now the clamping surface area at the business end is larger post-re-boring. BUT!- unless the OP is doing all his work at the diameter at which he bored or smaller, only the edges are making contact, and are freshly 'sharpened' and are biting in. Perhaps having the biting surface along the spindle axis spread out radially is what has cured the problem.

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One of the many people I spoke with suggested boring/grinding at a fairly small diameter, something an inch or so. That way any diameter larger than that has 6-point grip (the two outer edges of each jaw). My boring bar is 1.25" & the jaws were set to just clear the BB, probably 1.35" or so. The grinding stone on order is 1" so I plan to grind around 1.25" diameter.

Glad to hear that you have solved the problem but although I have used some dog rough old bell mouthed chucks in my time , I have not had the workpiece pushing back as you describe or is it that you were having to keep the tightening relatively low to avoid marking the work?

I had a chuck that I had written off because it ran out about .010 inch a few years back and a friend/customer that rebuilds machines offered to show me how they did it with the idea that I could do them myself in the future. Of course it would cost me with gun work down the road. Admittedly it was pretty simple. He had some hardened steel, knife edged rings and he selected one of the most common size of material that I used which was 1.5 inch. He clamped it into the chuck at the second groove in the jaws from the front and closed it to about what he called half operating pressure to preload it. He then removed the tool post and installed a tool post grinder and set the compound over to about 5 degrees and cleaned up the back of the jaws. He then measured the jaws with a star micrometer and moved the ring down a couple grooves and cut the front of jaws to the same diameter. It worked quite well and I have done a couple since with no complications.
It sounds much like the same procedure but just a different problem.

sable said:

... is it that you were having to keep the tightening relatively low to avoid marking the work?

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I tightened the handle til my eyes bugged out, going around all three pinions at least twice (6 times & could always get a bit of handle movement). Never did put the 18" tommy bar on the handle as Bison cautioned against that. It was physically impossible to tighten the jaws enough to prevent slipping. The steel handles hurt my wimpy hands so I finally added wooden covers (image below).

He had some hardened steel, knife edged rings and he selected one of the most common size of material that I used which was 1.5 inch. He clamped it into the chuck at the second groove in the jaws from the front and closed it to about what he called half operating pressure to preload it. He then removed the tool post and installed a tool post grinder and set the compound over to about 5 degrees and cleaned up the back of the jaws.

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That is a neat idea

Boring out "normal" flat or pie jaws is easy enough. The fact that even the steel ones are soft is a benefit. These top jaws run around 65 Rockwell (according to my hardness file set) so plunge milling the holes was slow & boring at 150 rpm was endless (at .003" per rev). Planning to grind at 50 rpm with the same feed. Start the machine at breakfast & it should have the jaws ground by lunch.

Finally found one photo of the jaws before boring. Looks like the contact was primarily at the tips. The factory grind had very little contact area & hopefully the much wider area after boring & grinding will be better.

Take some brown paper bag paper. Wrap it around your metal bar so that only 1 thickness of paper is between the jaw faces and the work. Make sure there is NO OIL on the jaws or paper.

Paper holds like crazy. I would NOT use brass shim as brass is a very slippery metal. So is aluminum. Try the brown,or other CLAY LESS paper. I use it all the time in my milling vise,under my tool holder,or any place I don't want slippage. It should make a great difference,PLUS,it will help protect your gun barrels.

DO THIS,no shit. This is valuable advice. Post your findings after you try it.

It would make sense. Paper is semi compressible and would dry grip where the jaws close tight and give a certain measure of traction in areas where the jaws don't make 100% contact to the workpiece. I use paper for protection on precision ground material and blued surfaces all the time to prevent the jaws from leaving footy prints.