CONJ COPOS 8 PÇS SORT IMP

2025-08-31

The chuck needs an adapter backplate anyway, so how about a new backplate which is is slightly off center (by as much as the the back surface is on the current one), so the error there is canceled out. the taper in the front would have to be reground this way, but the collet would sit perfectly straight in the chuck. alternatively a new backplate, but the back surface is machined on the chuck (ie. the regrinding you mentioned, but as it would only be on a new back plate, it is on a disposable part and even on a failure a comparison with the current back plate should give better measurements how it should have been (to machine a third one with that off center error measured before). and if it goes well....

2025-08-31

Rotate around.... come on James, youre beginning to sound like Keith Rucker. Lift up, lower down, part off...

2025-08-31

My rule of thumb was always .0005 tir on all 5c collets even using Hardinge collets

2025-08-31

I liked your trouble shooting steps very thorough. Thanks for the video keep on keeping on.

2025-08-31

Others have mentioned the need for a known-good collet, now that you are down in the range of where the import collet errors may be dominant. If the taper measures concentrically, then theres nothing else to do with the chuck for now. Of particular concern is that the collets are only contacting the chuck at their split points. That tells me that the collets are slightly oval in a way that tightening is not taking up.

2025-08-31

Its worth noting here that gage pins are not always perfectly round. Some pin classes are intentionally tri-lobed. I would suggest that you get a dowel pin and test the runout to see if you get the same results. I do think you taught a very important lesson with this video. Always take notes when you are disassembling something so that you can put it back together in the exact same way. Its especially easy to do these days since everybody has a smart phone with a camera in their pocket.

2025-08-31

spin up a solid bar between centers that otherwise is identical to a collet but without splits that wedge it in the chuck. then since it wont collapse and shrink into the chuck any error in the chuck mounting surfaces will be directly visible in solid collet once its pulled up/in and mounted. the solid collet will act like a gauge pin or other such things, but be instead of parallel or triangle shaped the end of it mounts as a 5c collet.

2025-08-31

yea grit!!!!! :D

2025-08-31

Смысл был вообще? Пол сотки вывел всего лишь.

2025-08-31

personally i dont see much benefit to taking it further unless you invest in more precise collets first

2025-08-31

Surprised that he didnt use his tool post grinder that he made 7 yrs ago.

2025-08-31

You could mount just the back portion of the chuck, and test the rear collet support area for concentricity. I would really look over that split in the chuck for anything out of the ordinary. Some 300 pound gorilla might have tightened the bolts enough to lift those areas. I have seen that on surface grinding jobs that have threaded holes.

2025-08-31

Nice job. More work but for accurate common sizes possible to internally grind few collets in situ? Even more work.....but if lathe spindle bore big enough make a drawbar collet chuck? Could register in spindle bore and thread on outside to hold in place perhaps. Got drawbar collets mounted directly in spindle on 80+ year old leinen lathe and run perfect and zero overhang from spindle bearing so nice and rigid, much better than Crawford d1-6 collet chuck on other lather (but obv larger lathe so likely to be worse I guess)

2025-08-31

You can build up material inside the taper by getting it chromed up to 1mm thick if you want. That how spindles are repaired and reground.

2025-08-31

Several comments - nice effort. I would suggest getting a reference 5C collet. Hardinge makes special super accuracy collets, they have 4 slots and the best TIR they offer. Not cheap and often used on tool grinders (I have a set for a Cuttermaster). Then a straight and round pin is needed to check TIR at the nose and as far out as the pin length permits. Ive found that drill rod and drill blanks are neither round or straight enough when in the tenths world. Dowel pins Ive bought from McM are straight, round, and are relatively cheap. (it kinda makes sense - bent dowel pins dont work). A set of these then can be used to measure 5C and R8 collets. A set by 1/8" steps to 3/4" wont break the bank, I bought the longest offered. Subsequently, I threw out a lot of R8 collets and some 5C. An R8 MSC brand set won, but I dont have any of the best brand name R8s. Then with your surface grinder you can tune up v-blocks to match and have the V bottom parallel with a dowel pin. Its fun to

2025-08-31

Impressive, axial runout could be futzed with in the backing plate, but then it would be back to the grind. Much better than truing a 3 jaw chuck.

2025-08-31

Very methodical and logical measurement process. I learned something, thats for sure. Thanks James!

2025-08-31

collets were riding on split points. Y might want to lighten those points on your cheap collets. So that the load point is divided more evenly through collet chuck. Your collets just going to grind and scrape your chuck again.

2025-08-31

What runout does the O.D. body look like?

2025-08-31

Nice job on the chuck. As others have said a high quality collet would make a big difference in what you are seeing for run out. Also why dont you drill a hole in the outer dia. of the adapter to fit a .500 dia. bar to tighten and loosen the chuck on the spindle instead of the strap clamp?

2025-08-31

*_Just cant trust chinesium. All my chucks are set tru made in USA or Europe. Same with collets. I always use the tenth indicator to zer everything out. So far no issues!!! Knock on Mahagony wood._*

2025-08-31

I have tried to drop a part on a finger. It only fell 10-20mm, and the part was not long and only about 50mm in diameter, but on the underside of my finger was the sled on the lathe, which didnt didnt budge... could feel that for a week

2025-08-31

I would never have guessed that a little pencil grinder would be rigid enough to give such a good finish. Well done

2025-08-31

Didn’t you make a grinder for your lathe a while back?!

2025-08-31

Cant tell you how many times ive had my knuckes smashed into the ways when knocking a chuck loose with rubber mallet. You always try to be ready but somehow we never are.

2025-08-31

Nice...

2025-08-31

Now this is quality content! But, sir, please, oh please next time use tens indicstor, its helluva eyesore trying to look in to those 0-3 thou idscrepancies..

2025-08-31

James, please get a lever DTI, the use of a dial gauge in this case is painful!

2025-08-31

You could go the swiss way, and get a morse taper reduction sleeve with a set of w12 or W20 collets to fit directly into the spindle and toss the 5c collet chuck...

2025-08-31

I would fabricate a solid piece of the collet and the other end to fit the tailstock. Center it. Lather it with grinding compound. Run the lathe on maximum speed and sliding the solid collet in. You will get it down to under a tenth

2025-08-31

You need to dress your wheel where you grind on the lead edge of the wheel, then redress the wheel and make a final skim cut.

2025-08-31

I use to use a cutter grinder spindle to grind in tapers never did i ever get runout less than .002 with a import 5c collet i purchased a set of hardinge high precision 5c collets i thinkyou got it better than you should have with import collets how many times are you going to need it any better but i understand why you do because but is it worth 2500 dollars for a set of hardened and ground precision collets i think you got a great collet chuck now i would bet the bearings in the spindle of the lathe will not hold 0008 for long unless you have already replaced them too you do great work always a pleasure to watch your videos from a 50 year retired machinist

2025-08-31

Had the same exact problem with the same chuck. Sold it, priced accordingly, to somone with the patience to bring it back to life. Ended up just going with a collet handwheel and spindle bore adapter. Great video!

2025-08-31

Talk about total neglect!!! So much of that could have been avoided. That rear end definitely needs to come out, the bearings have to be destroyed!

2025-08-31

Late to the party BUT Ive struggled with a similar issue and resorted to mounting an air die grinder. I got closer but never did get it perfect. Lots of time in it. Maybe Ill go back to it later.

2025-08-31

cant you make a reamer for that

2025-08-31

I just got one of those today and will be trying to bring it back to life. Thank you for the videos!

2025-08-31

Getting an old worn out chuck back to less than 1 thou of runout is extremely impressive. You should feel proud.

2025-08-31

Could it be the grease on the mating surfaces that creates the runout?

2025-08-31

Great job with the pencil grinder. I have been using them in a V block for years, mostly to true the face of diamond and borazon wheels. A shop i worked for used a pencil grinder on a cnc grinder for a very high speed head. Collet on pencil grinder not running true was the biggest problem.

2025-08-31

Well done James... Takes a lot of patience for that detailed analyzing...definitely paid off. Enjoyed....now its ready for action... ATB.....

2025-08-31

Like always great video. But in another hand I was wondering why you dont make hole in that adapter for removing it(as you can just put inside pin/screwdriver and rotate it), so you would not need to use strap clamp. Or that would mess balance of adapter too much?

2025-08-31

It may not be perfect but its a hell of a lot better than it was, great job James!

2025-08-31

I believe MrCrispin (@MrCrispinEnterprises) did this same grind in one of his videos. Worth a look.

2025-08-31

Hi James as a former machine tool maintenance guy , nice work! as others have suggested perhaps a know good quaility 5c collet is the next step. A 3/4" hardinge collet from their online store is $75 lyndex is also high quality and about half that. at the end of the day you do get what you pay for. the ultimate test for a spindle (runout and alignment) is a solid test bar . there is obviously a limit to how good an old collet closer and a low cost hobby lathe can be There is such a thing as " close enough"

2025-08-31

Try deburring the corners of slots in the import collet! the way it marked up the blue suggests high spots around the slotting. Other than that I think you have already got a huge improvement! A good watch!! Phil, UK

2025-08-31

I would assume there to be a ding in some of the mating parts of the chuck itself if theres runout. Its unlikely that the whole chuck would be bent in an accident. Another option is that someone just reground it to run true in their out of whack spindle. Did the body of the chuck run true?

2025-08-31

Vary nice job! I would call that good . I’ve been a machinist all my life and I build pool cues for a living. I have ground many chucks and you can only go so far before you start backpedaling.

2025-08-31

At this point, grinding the collet in might be the better option. Great work!

2025-08-31

I came across this phenomena many years ago with the run out in a 3 jaw chuck on a dividing head and the guy trying to get a mandrel to run true by resorting to hitting the back end of the chuck jaw with a copper punch in the vain attempt to get it to move a couple of thou..........without asking permission I re-machined the backplate register to give it a .005" clear and the rest is simple to get the part to run true.......this trick will work for any 3 jaw chuck when you just must have the part its holding to run true.