Lathe Chuck

Zebra13 said:
I could never figger out why they wouldn't have them at dead nuts 90's.
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With 3 pinions, 3 attachment bolts for the backplate and 4 adjustment screws there doesn't appear to be enough room. I'd like to take one of the older Buck's w/the 90° spacing apart and see how they did it. Maybe the older Buck's have only 1 pinion in them. I believe Jackie Schmidt has an older Buck w/the 90° adjustments. Maybe he could answer the question.

Edit: I looked at some pictures of the older Buck set-tru's. They appear to have only one pinion for jaw opening/closing. Probably why they had room for 90° adjustment screws. Some of the newer Bison and Buck set-tru's have 3 pinions in them although the latest Buck's appear to have gone back to one pinion and 90° adjustments. Bison still seems to have the 3 pinion and non 90° adjustment design.

Buck set-tru.jpg
 
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I use a Buck 6 inch with 6 jaws. Purchased about 20 years ago. The adjustments are at 90 deg and it wil hold something down
to around .135 dia. I love it
 
6 jaw chucks are trash magnets. They are made for thin wall work and tubing. If I did not have a specific need for a 6 jaw, I would not own one.

BTW that repeatability thing is only at a specific diameter, it is not modal. An adjust true chuck is no more accurate than any other chuck. That notion that a adjustable chuck is more accurate is just that it is misunderstood.

All chucks need to be throughly dissembled and cleaned and lubed when new, and periodically there after. 6 jaw chucks are high maintenance due to their design, and need to be serviced constantly.

If you have never performed service on a chuck, you will be shocked at the amount of chips they can accumulate.

Steel is the best, semi steel is OK, cast is junk.
 
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TRA, you are correct, We periodically have to take the big 3-jaw chucks apart on our lathes that we use a lot. Crap just accumulates in that scroll, and sooner or later, the thing will hardly turn.

I have an older Buck 3-jaw and 6-jaw Buck Set True chuck, and yes, the set true screws are 90 degrees apart.

I also agree that unless you are messing with thin stuff, a 6-jaw is more problems than they are worth. Mainly, if a piece is not perfectly round, not all of the jaws will hit anyway......jackie
 
4 jaws are pretty universal and in most shops, nearly maintanence free, absolutely a workhorse. 3 jaws are really good , but have
limited use. The 6 jaw set true is great for barrels, bolts etc. My 6 jaw will hold a firing pin well enough to turn down at .062
without chatter, Might do it in a collet, but not a 3 or 4 jaw. It serves me well, but it only does gun work.
 
Zebra13 said:
Gents,

I am looking at buying a new 6 jaw adjust thru chuck for my lathe. One thing that keeps popping up that I know nothing about is steel vs. semi-steel. The steel chucks are more expensive and advertise .0004 TIR repeatability. The semi-steel chucks are cheaper and offer .0005 TIR repeatability. The issue, as I understand it, is the semi-steel are more apt to wear quicker.

I am a hobbyist gun tinkerer, and my machines will never see production. I probably won't wear out a semi-steel chuck. But as I said, I don't know a whole lot about this, so I am deferring to those who do.

Any thoughts, experiences, advice, etc., would be appreciated.

Justin
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"semi steel" as it is called was first used in welded machine frames to kinda give the rigidity of cast iron and a lighter cost. It still flexes like steel, but seems to be fairly stable. I see no serious problem with using it in a chuck body (but I wouldn't). Most of the better chuck bodies start out as a cast steel blank or even a forging, and are completely machine out of it. The master jaws are usually made from cast steel or cast iron. The pins and such are also 4140. They all wear with general usage, and all need cleaning at least once a year. Some seem to have problems with that more than others do I might add.

The real difference in chuck brands and even styles is how well they hold up in a crash (gonna happen sooner or later). Buck is the best period, and easilly rebuildable by somebody that knows the craft. The Japanese chucks that some many OEM's are using today are a mechanical nightmare with a high failure rate (you probably won't use one of these!) If I were buying a cheaper grade of chuck, I'd simply buy the semi steel one. That extra one tenth won't mean a thing to the bearing pack in your lathe anyway. Just be sure to cut the jaws in after mounting, and make sure the adapter plate is running true with the spindle axis.
gary
 
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sbindy said:
I'm sure I am in the minority, but I prefer a 4 jaw chuck to anything else when I have to make something as perfect as possible.

Mike, I also use a copper ring between the jaws and work. I read about that on this forum a short while ago and it is definitely the way to go.
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I'm like you, I have yet to see an advantage with a six jaw chuck. A good Buck four jaw chuck that has the jaws cut in will handle anything we'd ever do in spades
gary
 
mike in co said:
ok, me thinks you guys are confusing chucks.
a tru set or clone is a scroll chuck BUT IT IS ADJUSTABLE. the entire chuck moves on its backing plate.
they are easier to set up than a four jaw, because holding force on the work pc is independent of the zero.
so one of the two of you that say your 4 jaw is easier to indicate , that has worked with a tru set, please explain how and why the std 4 jaw is easier ?? please

mike in co
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Mike, they make adjustable plates for three and four jaw chucks. The term scroll chuck is just a generic name determing the fact that the chuck body is adajustable. Some (actually the better ones) use a master jaw set that has tooling jaws bolted to them. You should do a skim cut with the jaws under a load to make them true. After doing this there is no reason you can't dial in a piece to a tenth and a half if needed.
gary
 
ok enlighten me..i have never seen a 4 jaw tru set or clone....
who makes one ??
mike in co
 
The best plan is to use soft jaws and forget all that adjusting. It's really a waste of energy chasing your chuck all over the place. If you want to machine true to your equipment you will use soft jaws. A scroll chuck is like a tire, they are wearing out every time you use it. You run a lathe long enough and you'll learn how to true up your work with a soft hammer, or a piece of brass or aluminum.

JFYI, the newer Bucks ain't what they used to be, jus sayin. If you have an old one send it out and pay the long dollar to have it reconditioned. You will be glad you did. The last 2 new ones I bought were a real disappointment.
 
so that is not the first comment by you that benchrest gunsmiths, hobby and pro...do not know what they are doing, that you know better.
so how about showing use what and how you do it and the results on paper.
for the record, using what i have learned here and my basic lathe skills i built my first 1000 yd br rifle...on paper....0.3 at 200 yds. i say these methods work.

mike in co
TRA said:
The best plan is to use soft jaws and forget all that adjusting. It's really a waste of energy chasing your chuck all over the place. If you want to machine true to your equipment you will use soft jaws. A scroll chuck is like a tire, they are wearing out every time you use it. You run a lathe long enough and you'll learn how to true up your work with a soft hammer, or a piece of brass or aluminum.

JFYI, the newer Bucks ain't what they used to be, jus sayin. If you have an old one send it out and pay the long dollar to have it reconditioned. You will be glad you did. The last 2 new ones I bought were a real disappointment.
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TRA said:
You run a lathe long enough and you'll learn how to true up your work with a soft hammer, or a piece of brass or aluminum.
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I regularly use nylon faced and small lead hammers to tap things in on all types of setups. Sometimes I use a lead hammer on the chuck body (set-tru) or a jaw on the 4 jaw to tap them in when I'm down to chasing the final little bit.
 
TRA said:
The best plan is to use soft jaws and forget all that adjusting.
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If the ID of the bore was consistently concentric to the OD then soft jaws would make sense but in this barrel chambering business adjusting an adjustable chuck of some sort seems worthwhile.
 
Way back when lathe chucks were mostly made in the US semi-steel generally meant cast steel as opposed to rolled or hammered and rolled steel. Most all larger chucks, say 24" or larger were generally machined from solid steel plate.

In todays import market semi-steel can be anything from pop bottles to cinder block.
 
TRA said:
The best plan is to use soft jaws and forget all that adjusting. It's really a waste of energy chasing your chuck all over the place. If you want to machine true to your equipment you will use soft jaws. A scroll chuck is like a tire, they are wearing out every time you use it. You run a lathe long enough and you'll learn how to true up your work with a soft hammer, or a piece of brass or aluminum.
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And you are chambering and threading rifle barrels with this method?
 
JerrySharrett said:
And you are chambering and threading rifle barrels with this method?
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I do. Even, and especially with a hydraulic chuck.

I gotta be honest, I never shop chucks... I had no idea there were 4 jaw combination chucks out there. Whoda guessed? Thanks WSnyder.
 
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I know of one prominent BR group shooter that believes as long as he can't SEE the wiggle, the barrel is lined up close enough. I also know about 1 in 20 of his barrels are keepers. But with enough oil wells.....
 
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