Buck Chuck Runout

[slughammer]

What would you consider acceptable runout for an Adjust True chuck when switching from one diameter to another?

I recently purchased a used 4" Buck Chuck and although it's clean and has a new set of jaws; I'm surprised at the amount of runout when switching from one diameter to another diameter.

Buck Chuck
(Checked with the carriage locked, about 1/8 from jaws with a dial test indicator. )
If I zero on 1/4" material, the runout on other sizes is
3/8 = .007
1/2 = .008
5/8 = .003
3/4 = .006
1 = .005
(If I zero on 3/8.... the runout on 1/4 and 1/2 are both .006)

I bought this to replace my old non adjustable 3 jaw Chuck. Checking with the same standards.
OLD CHUCK
1/4 = .0045
3/8 = .0040
1/2 = .0010
5/8 = .0035
3/4 = .0035
1" = .0050

I understand that a 4 jaw is the way to dial in critical parts. I was just thinking that the scroll of this Buck Chuck has been damaged if any of these readings are over .003.

Sent from my SM-G970U using Tapatalk

[M-Tecs]

Yes that amount of runout is high. I have 3 of the Buck 6 jaw Adjust True chucks. My worst one is about .0015" runout when changing sizes.

[HWooldridge]

Sounds like way too much. I have a Pratt Burnerd on an old Clausing that runs about a thou with CF material.

Does your Buck chuck have the Ajust-Tru screws? I have never owned one but those are supposed to help adjust runout quickly.

I would probably remove the chuck, pull the jaws and inspect the scroll under good light. It may have been wrecked in the past - perhaps you will see something.

[country gent]

One shop I worked for bought a new 6 jaw adjust true buck chuck the best we could get it was .0015 but it was consistent thru the various sizes. Is this a new chuck or used? On a new chuck I would consider your numbers unacceptable, on a used chuck all bets are off.
If this chuck has 3 handle sockets use the same one each time find the best and mark it X

1) pull the removable jaws and check on the "solid " jaws to see if they are the same. When ground in these are ground roughly .010 bigger so less wear or damage on them.
2) Disassemble and clean well regrease. grit dirt swarf can affect the scroll to jaw alignment..
3) While apart look for wear and damage on the scroll and jaws also the T slot bearing guides, lightly stone these to remove butts and smooth

If nothing helps you can try the old way and ring and grind it in but I doubt this will help with the varying run out
It takes very few times of a pipe or tapping in to spring the scroll or jaws or to damage the jaws

[bangerjim]

I took a 4" and an 8" standard 3 hardened-reversible-top-jaw chucks and made them into "adjust-true" style chucks several years ago.

Now, once dialed in on my SB toolroom lathe, I get 0.00035" runout on anything I put in them. What you are getting is NOT acceptable, at least for an adjust-true style chuck.

Have you checked the run-out of just your headstock spindle??????????????

Be sure what you are using to chuck in the jaws for the tests is perfectly ABSOLUTELY round and does not have any malformities in it. I use NEW drill rod and some tool room standards for largest sizes. Do not trust standard steel round stock!!!!!!!! OR drill bits! You need tool room standards when dealing with any small run-out measurement testing/verification like that.

That's why most handy-man home lathe owners are perfectly happy with ±0.003 or so run-out. They do not need or have the tools and techniques to measure anything more accurately.

Good luck!

[country gent]

I would think if the scroll is good then once zeroed it should be good thru its range

[Alasgun]

I would agree with most of what’s allready been stated; but would add to be sure the jaws are in the chuck in sequence. Especially one with replaceable top jaws.

[country gent]

There are to many out there that think a chuck has to be tightened with a length of 2-3 foot length of pope on the handle to hold. This added torque springs the scrolls where its applied,is hard on the bearing surfaces and the drive gear teeth. In the smaller chucks these are small and even more susceptible to damage.

Im still thinking a good cleaning inside fresh grease may help but it also may take a new scroll and some work rebuilding the mating surfaces. On a chuck this size that may be prohibitive.
In one shop the lathe chucks were "tuned" roughly every 5 years, taken apart cleaned relubed and ground in to their machines spindle, It is amazing how much crud gets up in there. How the thin film of grease holds all that. We would pull a chuck from a machine and the first thing was check that it was that machines chuck. Occasionally it wasnt they had gotten swapped when changing from collets or 4 jaws back. 7 monarch lathes all with the same spindle mount this is likely to happen. They were then checked, cleaned and if needed ground in then cleaned again and re lubed Normally the regrind was done to clean up the jaw surfaces as much as to bring it back to true. .003-.005 would normally do the job but occasionally there would be score lines that would take more.

When a short stub is chucked out at the ends of the jaws then over tightened sevveral things happem, the scroll is sprung, the jaws cock in the 5 slot putting the scroll and teeth in a bind and warping the T slot they ride in, the fronts of the jaws are distorted and the open section isnt. Want to see this blue a 2"-3" pin up and chuck it then remove it chances are the jaws will show ink in the center but not front or back. Ocasionaly this needs to be ground out making the jaws straight again

[HWooldridge]

Another thing you see in a production environment is a wear pattern in a particular range. The chucking system might be used to run .750 material over a long period of time so the movement is small. Same thing happens with the bed - you'll often see 12" of wear immediately in front of the chuck on a 60" bed. The saddle will have the gibs tightened so the carriage can't move toward the tail without binding.

We had a 16"x54" Monarch at a place where I worked in the 80's. The machinist would run the carriage under power all the way back and forth once a day to balance the wear near the chuck.

[Jeff Michel]

I have found with my "adjust-tru" chucks is that if I chuck stock that is significantly different in diameter than what I dialed it in for originally, there will be run out, sometimes quite a bit. I just use mine for production runs when the stock is all the same diameter. I just make sure it hasn't changed with the different sized stock when I'm setting up. Country Gent has given very good insight regarding scroll chucks in general. In my experience, second hand scroll chucks are seldom a bargain, if they are sprung/need jaws, etc. you will have close to the cost of a new chuck in the rebuild. I have a friend in Cleveland who rebuilds chucks of all sorts, after he priced a rebuild on a cute little 5" Pratt Burnerd 6 jaw I had acquired second hand. I dropped it in the scrap barrel by his bench.

[sparky45]

Here's a quick tip on truing a 3 Jaw. Go to about the 2:30 mark if you already have the correct alignment of the Jaws.
https://www.youtube.com/watch?v=gnd_g65qiMQ

[gishooter]

Slughammer: I agree that is more than acceptable. Are the new jaws you purchased Buck brand or after market? And as already mentioned the jaws (regardless of brand) might need to be in different slots.


I would not recommend beating on the chuck jaws (adjustable or standard) as shown in the video.
That 3 jaw chuck in the video would probably benefit from having the jaws reground.
I do not like using rings to load the jaws when grinding. Preferred technique to preload the jaws shown in video link below. But they are using a boring bar. I use a tool post grinder.
https://www.youtube.com/watch?v=2_GAPDtvhzs

I have three Buck adjustable 3 jaw chucks in my shop. At tech school we had the Bison version.

[W.R.Buchanan]

OK let me interject some pertinent information in this conversation. The whole reason why these chucks have the runout adjustment is so that you can zero them out for a particular job. It is not a one size fits all type of thing. it is adjusted for one diameter and then if you require some other super accurate low runout for a completely different job you put and indicator on it and tweak it for that diameter.

Since the Scroll is nothing more that a flat plate of Cast Iron with a circular thread cut in it, and since the jaw carriers are all machined in separate operations there is no way that the chuck can have nearly zero runout for all the diameters you might want to turn. There will be variations in the scroll and the chuck maybe have been used for one diameter part and the scroll and jaw carriers worn in that place. that is different form the sizes you used.

That said I have my 6" Buck Chuck for my Hardinge Chucker. Since all my machines have the same threaded spindle nose I can run it on my Chucker, DSM, My Omniturn GT Slant and even on my Hardinge Head indexing fixture. If I have something that absolutely has to be dead nutz, I will indicate the chuck in, however I haven't done that in the last 2-3 years and the chuck has been on and off the machine a hundred times since the last time. For the stuff I do it is close enough. Its a chucker with 8 stations on the turret, so all the operations I do on any given part will be done in one chucking and then parted off or just left alone.

Also if you think you can "Remove" a part from a chuck and then put it back in and have it run true, you are mistaken. It never happens. That is why they invented Turret Lathes in the first place.

What you need to do is chuck up a 3/4-1" dia. Dowel Pin (Dowel Pins are actually round) and indicate the chuck in using that. Sweep the pin at about 1/4" from the chuck jaws and zero the chuck out. Then sweep it again about 1" out from the jaws or father out if you have a longer pin and see if the zero repeats. if it doesn't, then Either the jaws on your chuck need to be bored (Like Soft Jaws) or the headstock of your lathe is cockeyed and needs to be indicated in parallel to the bed.

It is not unusual for a headstock to be knocked out of alignment, and it doesn't take much of an Idiot to do it.

Once you have eliminated all the other variables you can have a closer look at your chuck. And after 40 years I have NEVER heard a bad word about any Buck Chuck!.

If you need things to run truer than what you are getting with your chuck you need to be running collets anyway.

Randy

[M-Tecs]

The current owner of the Buck line is Hardinge. Depending on the model they guaranteed repeatability of .0005" or .001" TIR. The older US made were awesome and would hold the claimed tolerances when new and not abused. When they switched to Poland not so much. I sent two of them back. Currently I believe Bucks's Chucks are made in Taiwan and I have not purchased or used them.

The three I own are US made. All three were purchased as NOS at a business auction.

[Scrounge]

What would you consider acceptable runout for an Adjust True chuck when switching from one diameter to another?

I recently purchased a used 4" Buck Chuck and although it's clean and has a new set of jaws; I'm surprised at the amount of runout when switching from one diameter to another diameter.

Buck Chuck
(Checked with the carriage locked, about 1/8 from jaws with a dial test indicator. )
If I zero on 1/4" material, the runout on other sizes is
3/8 = .007
1/2 = .008
5/8 = .003
3/4 = .006
1 = .005
(If I zero on 3/8.... the runout on 1/4 and 1/2 are both .006)

I bought this to replace my old non adjustable 3 jaw Chuck. Checking with the same standards.
OLD CHUCK
1/4 = .0045
3/8 = .0040
1/2 = .0010
5/8 = .0035
3/4 = .0035
1" = .0050

I understand that a 4 jaw is the way to dial in critical parts. I was just thinking that the scroll of this Buck Chuck has been damaged if any of these readings are over .003.

Sent from my SM-G970U using Tapatalk

Not used one myself, but have been told by guys that have, that to get any adjustable chuck accurately centered, you need to adjust it at a specific diameter. Change diameters, and it won't be as accurate because the jaws are not gripping at the same location on the stock. Really high quality chucks it may not be far off, but it will almost always be off some. If the accuracy is necessary for what you're doing, take the time to do it right. Adjust at the diameter you need the accuracy at.

I've just faked what I call a "whack true" collet holder. I've got an ER32 collet chuck mounted on an import faceplate for my Atlas TH42. I flubbed the register diameter, and found that the holes in the backplate didn't match those in the chuck. Could have faced it back a bit, and tried again, but just cut the register a bit smaller, and whacked it into .001" runout before tightening the screws. The collet chuck is a cheap import, as are the collets, and for them .001" is fine for now. Once I have a mill running well, so I can drill the edges of the collet chuck mounting, I'll make it a real adjustable. But I expect to have to whack it into better alignment if I change collets, for now, too.

And someday, when I win the lottery, I'll buy a real chuck.

Bill

[country gent]

Several things have a affect when you change sizes and they are all hard to check or verify. The scrolls mount or bearing in the chuck body, the scrolls consistency at the time wear and damage all affect this, the mating scroll in the jaws, fir of the jaws in the slots chuck jaws can and will cant under pressure. then is the radius on the jaws where they grip on small its on the center line between the edges on bigger it changes to the edges with the center open. Even the stock softer stock may compress different than harder allowing the stock to shift. An interesting test is to put a long Jaws become bellied or flared thru use pin in the chuck check it at the jaws then 4-6" out. It should be very close to the same but seldom is do to jaw cant and not holding true. Jaws get bellied or flared over time not allowing them to grip true.

[kenton]

I agree with what W.R. Buchanan says. I work in a shop that has a bunch of Buck chucks that are going on 30 years of use and getting worn out. One thing no one seems to want to acknowledge, especially when it comes to machining, is that everything is a consumable. Nothing lasts for ever. In a home shop where a given machine might run an average of 2 hours a week stuff should last a while. In a for profit machine shop time is money, stuff gets run hard until it is worn out and replaced. Most people check for wear when buying a mill or a lathe but it gets forgotten about when it comes to accessories.

That said I would zero your chuck near the center of your expected range, 5/8 maybe and check from there. Weird things happen when you start near the extremes of travel.

What you are seeing is similar to what I see at work. If I need it to be more concentric then I know I will have to dial it in before I start. As was stated before the bigger issue is if the chuck is bell-mouthed, or if it is worn enough so the chuck is only clamping on the back of the jaws while the fronts are splayed out. I just retired a chuck at work for this. Yes, they can be ID ground but if the wear is uneven then you have a chuck that only holds well at the diameter you ground it at.

[bangerjim]

And someday, when I win the lottery, I'll buy a real chuck.

Bill

Why not do as I did and MAKE ONE from a decent quality standard chuck?


banger

[ulav8r]

Another source of error, if you are trying to hold tight tolerance is the stock you are working with. If you true the chuck with a gage pin and you then use t&g(turned and ground) rod of the same diameter, you should get decent results. If you true with the gage pin and then you use a different size of cold rolled, there is less chance of good results. If you use anything other than a gage pin to adjust the chuck, rots of ruck.

[Willbird]

One thing I have seen in the past is that marking and using one pinion all the time can sometimes make any self centering chuck more consistent. This if for the chucks that offer multiple pinions to tighten the chuck.

Bill