4-jaw scroll chuck

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SteveM
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4-jaw scroll chuck

Post by SteveM »

I'm a sucker for a good deal, and I'm a sucker for lathe chucks (I now own 10), so when a good deal on a chuck comes along, well, let's say the space between me and that chuck is as dangerous as between, as they say in Washington, Chuck Schumer and a microphone.

I got a good deal on a Bison 4-jaw scroll chuck. The jaws on this chuck move in unison as on a typical 3-jaw.

The chuck came with soft jaws which were cut to fit a specific job.

A set of four hard jaws came up on ebay for a reasonable price (like 1/4 of the original retail price), so I grabbed those.

Took the chuck apart, cleaned it all out, greased the gears and oiled the scroll with Vactra.
4JaawScroll.jpg
Now I need to make a backplate.

This is something I will rarely use, but when I do, it will be useful. My dad had one on a straight shank he would hold in the set-tru 6-jaw for when he had to make a bunch of parts with square stock.

Oh, and the 10 chucks?

I have 3 4-jaw chucks, one with the jaws facing in, one facing out and one with two in and two out - almost never have to swap jaws.

I have a 3-jaw that I picked up cheap because it only had outside jaws, but now I don't have to swap jaws, just swap chucks.

I picked up a 3-jaw that has 2-piece jaws. Got it cheap because it was missing the jaw tops and hard jaw tops generally cost a bloody fortune. I made soft jaws for it. You can also get soft jaws cheap from US Shop Tools.

Steve
John Hasler
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Re: 4-jaw scroll chuck

Post by John Hasler »

Even I, stingy as I am, have five lathe chucks (counting the two Jacobs headstock chucks) as well as three faceplates. I often find it useful to be able to remove a chuck with a part in it so that I can use the lathe for something else without losing my setup.

The small three-jaw needs its jaws ground, though. It's bellmouthed.
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NP317
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Re: 4-jaw scroll chuck

Post by NP317 »

'Makes me feel minimal, with just 3 chucks for my lathe:
3-jaw, 4-jaw, collet chuck.

Yesterday, while turning 4" diameter rings, I had to reverse the 3-jaws 4 times!
But that's about the same amount of work as swapping out chucks...

And those 2-piece jaws are mightly clean, because I brass-wire-brush those mounting surfaces clean, every time the jaws get swapped!
RussN
SteveM
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Re: 4-jaw scroll chuck

Post by SteveM »

NP317 wrote: Fri Apr 17, 2020 10:57 am Yesterday, while turning 4" diameter rings, I had to reverse the 3-jaws 4 times!
But that's about the same amount of work as swapping out chucks...
Don't know about you, but swapping chucks for me is a lot faster than unscrolling and rescrolling to swap jaws (and I remove and replace the chuck to do it, so the swap only adds to it).

I was polishing the back of that little 3-jaw and needed the outside jaws. 15 seconds to swap chucks.

If I had to swap jaws four times, I would have pulled my hair out, which is good since I'm not getting a haircut anytime soon.

As an aside, I am machining some parts for a barber, and I think we are going to work out a trade.

Chucks with only the outside jaw sell for cheap on ebay, because the demand for inside jaws (or preferably both sets) is greater. It's worth the investment.

The chuck I use for soft jaws is a 6" brand name chuck, like Union or Cushman, that I got for $60 from Plaza Machinery. I made my own aluminum jaws but then found that US shop tools sells them for so cheap, it's not worth the time to make them.

Steve
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Bill Shields
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Re: 4-jaw scroll chuck

Post by Bill Shields »

i miss him (Joe @plaza)
Too many things going on to bother listing them.
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BadDog
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Re: 4-jaw scroll chuck

Post by BadDog »

I don't blame you. I wouldn't mind at all having a 4 jaw scroll chuck, but it would have to be a good deal since I don't NEED it. It's not just for square (or divisible by 4) sided material. The opposed jaws provide more rigid support when working on larger pieces.

But the one I really want is the 4 jaw independent scroll chuck. On those you can adjust the 4 jaws to hold the part as required. Then the scroll can release/grab repeatedly without having to repeatedly dial the part. As long as you don't need a really high degree of accuracy, with a quality chuck, that could be the best of both worlds. Alas, I've never found one with D1-6 for a good deal.
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SteveM
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Re: 4-jaw scroll chuck

Post by SteveM »

BadDog wrote: Fri Apr 17, 2020 5:04 pm But the one I really want is the 4 jaw independent scroll chuck. On those you can adjust the 4 jaws to hold the part as required. Then the scroll can release/grab repeatedly without having to repeatedly dial the part. As long as you don't need a really high degree of accuracy, with a quality chuck, that could be the best of both worlds. Alas, I've never found one with D1-6 for a good deal.
I actually have a Pratt & Whitney chuck that is a 3-jaw scroll chuck that has independent adjustments on each of the jaws. I suppose it's an early method of making a set-tru chuck. This chuck is for a Pratt & Whitney #3 lathe, which probably dates to the 1910's-1920's.

Steve
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NP317
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Re: 4-jaw scroll chuck

Post by NP317 »

Note: A careful read of my comments on reversing jaws referred to them as "2-piece jaws."
Two allen-head bolts hold each jaw in place on their base. No scrolling.
And the D-5 chuck mount is about the same amount of time and effort to change chucks due to the requirement to carefully clean all mating surfaces.
Not counting the damage to my back.
I can more easily lift those small removable jaws...
RussN
shootnride
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Re: 4-jaw scroll chuck

Post by shootnride »

BadDog wrote: Fri Apr 17, 2020 5:04 pmBut the one I really want is the 4 jaw independent scroll chuck. On those you can adjust the 4 jaws to hold the part as required. Then the scroll can release/grab repeatedly without having to repeatedly dial the part. As long as you don't need a really high degree of accuracy, with a quality chuck, that could be the best of both worlds. Alas, I've never found one with D1-6 for a good deal.
I have an 8" 4 jaw independent scroll chuck that I bought used a few years ago. I find that the repeatability when removing and re-chucking a part using the scroll isn't that good. Seems that I usually have to dial the part in again and make a little adjustment. It's generally not too far out so the adjusting is fairly fast.

Ted
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BadDog
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Re: 4-jaw scroll chuck

Post by BadDog »

Thanks for the feedback.

Yeah, that would make it less useful. But still, depending on how bad, for a lot of "not round/concentric) things it might be good enough. And, I guess it also depends on how much is paid. For what I've seen priced (and passed on), it better be pretty darn close or I'm going to be pretty unhappy. For the price I have acquired chucks at, as long as I knew what to suspect, I could live with it. Like a dividing head, it's not something I have a pressing need for, but if I find a good deal like I did on my dividing head, I'll be bringing it home. ;)
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SteveM
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Re: 4-jaw scroll chuck

Post by SteveM »

BadDog wrote: Mon Apr 20, 2020 12:55 am... it's not something I have a pressing need for, but if I find a good deal ... I'll be bringing it home. ;)
My philosophy too.

I balance "what are the odds I will use this and how much" with "how much can I get it for".

Steve
shootnride
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Re: 4-jaw scroll chuck

Post by shootnride »

I just wanted to do a follow-up on the post I wrote above about the 4-jaw scroll/independent chuck. As I said, I purchased this chuck used on e-Bay several years ago and have never been really satisfied with it's performance but never took the time to really look into why it's accuracy wasn't up to par. The chuck is a quality piece made by Rohm in Germany and I have two other Rohm chucks that I have been very satisfied with so I thought it was unusual that it's performance was so poor. So, after making the post above, and getting kind of bored with this Chinese flu lockdown, I decided to get serious about looking into the chuck. I have used it for chucking irregular work pieces and it seemed to work fine, but any time I attempted to dial-in something round, it was terrible. So, I took a piece of 3/4" ground HSS round stock and chucked it up. I could see daylight between the work piece and the outer ends of the jaws (obvious bell mouthing) I could slide a .004 or .005 feeler gauge in about half the depth of the jaws. I removed the jaws from the chuck body and tried to determine if there was any significant obvious wear in the T-slots that the jaws ride in and to see if I could detect any significant movement of the jaws in the T-slots that would give the effect of bell mouthed jaws. I was not able to detect any wear, so I decided it was time to try my hand at grinding chuck jaws.

Well, I don't have a tool post grinder and didn't want to invest in one for this one job, so I decided to see if I could set up my pneumatic die grinder to do the job (I know, not exactly the ideal tool for the job). I made a mount out of some scrap I had on hand, got everything dialed in concentric with the lathe spindle and proceeded to grind the jaws. It was a very slow process but I am very satisfied with the outcome. I can now chuck up that same piece of 3/4" HSS ground stock, dial it in to within .0005", remove it using the scroll and replace it multiple times and it will consistently dial in at .001 or less.

So I suppose that chuck won't just be sitting on the work bench collecting dust in the future.

Ted
Some people raise the IQ of the room when they enter.........others when they leave.
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