# 3-jaw self-centering chuck: standard or precision?



## wquiles (Mar 7, 2008)

I am getting closer and closer to getting my 1HP variable-speed HF 8x12 running (I will be wiring the 220V controller soon), and I am considering a nice quality, 6" dia, plain back, 3-jaw self-centering scroll chuck for the HF12 (of course I will have to make a mounting plate for it). I have seen several options:

1) Cheap/no brand chuck from Internet/Ebay - about $60-100 or so (varies greatly in price)

2) Looking at the Enco catalog, I can buy a Bison "normal" chuck for $241 (on special currently for $173.95)

3) Looking at the Enco catalog/special, I can buy a Bison "precision" chuck for $428.83 (on special currently for $295.95)


Questions: 
1) Bison - good brand, right? Others I should consider?
2) What makes the "precision" version more expensive? Would it improve repeatability and such?
3) I plan on making an adapter plate with some adjustability as shown here:
http://warhammer.mcc.virginia.edu/ty/7x10/vault/Lathes/7x10-7x12-Projects/SetTruBackplate/
Does this sound good, or are there 6" chuck adapters already available for the HF8x12?


Will


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## Torque1st (Mar 8, 2008)

For real precision work get a 4-jaw chuck and indicate your part in as close as you need. I consider a 3-jaw just good enuf for "quickie" work where precise centering is not needed. Collets are good for some production work.


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## wquiles (Mar 8, 2008)

Good point on the collets. I already have ER-40 collets, so I am set for precision work for "small" parts (1.023" or less in my case). I just want to get a "good" 6" 3-jaw for larger parts, working on Mag bodies, Mag heads, and projects in the 3-5" range (larger than my current 4" 4-jaw in my 7x12 can handle).

Will


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## TranquillityBase (Mar 8, 2008)

Hi Will,

I have a Bison scroll chuck, and I have been very satified with the performance, and the quality of the chuck.


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## Anglepoise (Mar 8, 2008)

wquiles said:


> Questions:
> 
> 2) What makes the "precision" version more expensive? Would it improve repeatability and such?
> 3) I plan on making an adapter plate with some adjustability as shown here:
> ...



Precision chucks will definitely improve on run out and repeatability. 
Get the best you can afford. To get this quality, the scrolls are hardened and ground as are all the sliding surfaces. Also hand fitted and matched.

Having a small amount of adjustment on the backing plate will allow you to 'adjust' for Zero run out, but at only one diameter. Still a very useful trick
if you are doing allot of work at a constant diameter.


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## wquiles (Mar 8, 2008)

Thanks guys - 6" Bison precision it is !!!

Will


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## Torque1st (Mar 8, 2008)

For a very small price difference over the regular price for the standard chuck that is a good deal.


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## modamag (Mar 9, 2008)

Will, personally I WOULD NOT put $300 down on a 3-jaw chuck. At that price range I would get a 6-jaw chuck or 4-jaw chuck.

I recently picked up a Buck Ajust True 6" 6-Jaw chuck and have been using that thing just as much as my 5C collets.

Regardless on which chuck you get, you will need to grind your jaws to get the last thous IDR out.


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## will (Mar 9, 2008)

I use a regular 3 jaw chuck for all my work. I did grind the jaws when I first started to use it. Collets will give you the greatest repeatability, good for production work. 

If you work on Maglites you will find out that some of the machined surfaces are not concentric with others. The knurled areas may or may not be. 

If you want dead on - get independant jaws, If I have something that needs better centering, I put a piece of cellophane or a paper shim under one or two of the jaws.

Another option - see if the chuck can take soft jaws. 

what is the max opening of the chuck?


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## wquiles (Mar 9, 2008)

will said:


> I use a regular 3 jaw chuck for all my work. I did grind the jaws when I first started to use it. Collets will give you the greatest repeatability, good for production work.
> 
> If you work on Maglites you will find out that some of the machined surfaces are not concentric with others. The knurled areas may or may not be.
> 
> ...


Thanks on the tips!. Opening? I am not sure, but the Thru Hole is 1.65" which should hold a D mag body inside the chuck body, with max. grip with the jaws for a little better grip/stability. I need to investigate the soft jaws - where is using these useful?





modamag said:


> Will, personally I WOULD NOT put $300 down on a 3-jaw chuck. At that price range I would get a 6-jaw chuck or 4-jaw chuck.
> 
> I recently picked up a Buck Ajust True 6" 6-Jaw chuck and have been using that thing just as much as my 5C collets.
> 
> Regardless on which chuck you get, you will need to grind your jaws to get the last thous IDR out.



You mean something like this?
http://cgi.ebay.com/Buck-Lathe-Chuck-6-Jaw-Ajust-Tru-6-Self-Centering_W0QQitemZ290109923346QQcmdZViewItem

Also, how one goes to "grind your jaws"? The only thing I can imagine is to insert a ring on the outside of the jaws, open the jaws until it grabs the ring on the outside, and then use "something" for the grinding - right? Any more details on how to do this?

Will


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## Mirage_Man (Mar 9, 2008)

modamag said:


> Will, personally I WOULD NOT put $300 down on a 3-jaw chuck. At that price range I would get a 6-jaw chuck or 4-jaw chuck.
> 
> I recently picked up a Buck Ajust True 6" 6-Jaw chuck and have been using that thing just as much as my 5C collets.




Jonathon, If you have any idea where one can find a Buck or Bison 6-Jaw for close $300 please let me know. I've been lusting for one for quite some time.


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## modamag (Mar 9, 2008)

*wquiles: *Exactomodo! Those are the ones! Another one to consider is the Pratt & Burned (PBA) SERITE chucks. One of my friend have this and absolutely love them.
Keep in mind these chuck cost more than our lathe so don't bundle this in you sale when you upgrade to a larger lathe 

When I got my first lathe Seig (C6B) I went through all sorts of means in attempt to get <0.001" TIR. I took the route of Lathemaster adjust true collet chuck. It works great if you only do small parts (<1.125"). Switching between 3-jaw and collet chuck was a major PITA. It normally take me 2-3 hours to do it. Most of this time was to fight against the POC backplate. If I had known I would have just true my 3-Jaws and called it a good day.

You asked how to grind the jaws. There are two methods that I know of.

1) Inside Jaws
a) Make a set of jaw lock shims. I like this method the most because you can grind the entire length of the jaw at one time. A guy from the Houston club documented it here.
http://www.homemetalshopclub.org/news/aug04/aug04.html#truing

b) As an alternative is to make a 1/8" thick ring, so your grinding wheel can clear this ring to grind the back end of the jaw. First you mount the ring near the back, grind the middle and front. Then move your ring to the front to grind the back.

2) Outside jaws 
Make two rings. Mount the ring and grind the alternate jaws

As for the grinder, your Dremel would work fine instead of spending hundreds for a Dumore. The trick is the fixture to keep it tight on your compound.

Remember, in machining we deal with thous, while grinding it's more like tenth and hundredth of thous.


*Mirage_Man :* eBay and local auction would be your best bet. At one time I had three different Buck Ajust True 6-jaws chucks. I bought one from ebay for $330+shipping but didn't have the mounting plate for my lathe. I didn't have the time nor taper attachment to make my own so I snagged two more ajust true from a local shop that closed out for $700. Now I'm a very camper. Being able to go from collet to chuck in less than 10s.

I still have one chuck left if you want.






Note that the collet & collet lever are still installed when the Buck 6-jaws are mounted.


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## Mirage_Man (Mar 9, 2008)

Modamag,

I check ebay every once in awhile but I have never seen one that has a 2+1/4" x 8 threaded back plate for my lathe. They are almost always D1-4. Not to mention they are usually beat to death anyway. I really would prefer the hardened reversible jaws as well.

I just can't justify spending $1000+ on a new chuck and back plate when I only paid $675 for my lathe. Granted I got a good deal on the lathe but still... Now If my plans work out and I end up with a new/er lathe in the near future I would then seriously consider dropping the cash on a new chuck.


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## will (Mar 9, 2008)

soft jaws are usually made of aluminum and screw on to the standard jaws. The advantage to them - you bore them out to the outside diameter of the part you are going to work on. Boring them out on the lathe makes them true, and gives the greatest surface area to grab the part, 

I remember that Brian had a set on his lathe. 

I used a dremel to grind the jaws on my lathe. be careful with the dremel stones, some wear away very quickly.


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## Mirage_Man (Mar 9, 2008)

will said:


> soft jaws are usually made of aluminum and screw on to the standard jaws. The advantage to them - you bore them out to the outside diameter of the part you are going to work on. Boring them out on the lathe makes them true, and gives the greatest surface area to grab the part,
> 
> I remember that Brian had a set on his lathe.



I still do but like you said they are really only good for one diameter.


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## wquiles (Mar 9, 2008)

4 of these Bison 6" 6 Jaw Set-Tru Lathe Chucks for sale now on Ebay - currently $400 each ...
http://cgi.ebay.com/Bison-6-6-Jaw-Set-Tru-Lathe-Chucks_W0QQitemZ150223001426QQihZ005QQcategoryZ25292QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Will


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## Mirage_Man (Mar 10, 2008)

wquiles said:


> 4 of these Bison 6" 6 Jaw Set-Tru Lathe Chucks for sale now on Ebay - currently $400 each ...
> http://cgi.ebay.com/Bison-6-6-Jaw-S...ryZ25292QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
> 
> Will



Yup, saw those. The seller has "(0)" feedback. I don't know about you but I'm not about to make a $450+ gamble.


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## wquiles (Mar 10, 2008)

Mirage_Man said:


> Yup, saw those. The seller has "(0)" feedback. I don't know about you but I'm not about to make a $450+ gamble.



Same here. For now, I am sticking with the new Bison high precision (I need something "now" to get the 8x12 running), but from now on I will be on the lookout for one of those 6-jaw units - I can always sell the Bison later and keep the "good" one!

Will


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## Mirage_Man (Mar 11, 2008)

Well thanks to J&L having a 25% off sale I bit the bullet and ordered the Bison 6-jaw chuck along with a few other things I've been needing but holding off on . The discount just pushed me over the edge :laughing:. I've been saving for a new lathe but I figure like you Will I can always use the new chuck on any lathe by changing the back plate.

Edit: I just happened to check Enco's site and they had the same 6-Jaw chuck for almost $200 less even with J&L's promotion! So I canceled the chcuk order from J&L and ordered it from Enco instead. Funny thing is the back plate was cheaper at J&L so I just left that alone.


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## modamag (Mar 11, 2008)

Great snag Brian, you won't regret the 6 jaws.


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## Mirage_Man (Mar 11, 2008)

modamag said:


> Great snag Brian, you won't regret the 6 jaws.



I sure hope so. This sets me back a little from getting the new lathe.


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## jayb79 (Mar 12, 2008)

Will,

You really will want an adjustable chuck, be it a 3 or 6 jaw. The adjustable part allows you to indicate anything you put in the chuck so it will run true.
Here is another link
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1785724&PMT4NO=0


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## precisionworks (Mar 12, 2008)

An old time machinist showed me this trick, which involves boring a small recess in the end of the jaws on a 3 or 6 jaw chuck. Handy as pockets on jeans when you need to surface or thickness a spacer, and much faster than using the surface grinder. You cannot be real aggressive on the cuts, as there are only six tiny contact points on the work, except at the diameter at which the jaws were bored. Still very capable and something we used daily when I worked as a machinist.


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## wquiles (Mar 13, 2008)

Mirage_Man said:


> Well thanks to J&L having a 25% off sale I bit the bullet and ordered the Bison 6-jaw chuck along with a few other things I've been needing but holding off on . The discount just pushed me over the edge :laughing:. I've been saving for a new lathe but I figure like you Will I can always use the new chuck on any lathe by changing the back plate.
> 
> Edit: I just happened to check Enco's site and they had the same 6-Jaw chuck for almost $200 less even with J&L's promotion! So I canceled the chcuk order from J&L and ordered it from Enco instead. Funny thing is the back plate was cheaper at J&L so I just left that alone.



Brian, which part # did you end up buying?

Will


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## wquiles (Mar 13, 2008)

precisionworks said:


> An old time machinist showed me this trick, which involves boring a small recess in the end of the jaws on a 3 or 6 jaw chuck. Handy as pockets on jeans when you need to surface or thickness a spacer, and much faster than using the surface grinder. You cannot be real aggressive on the cuts, as there are only six tiny contact points on the work, except at the diameter at which the jaws were bored. Still very capable and something we used daily when I worked as a machinist.



Cool tip on the boring at the end of the jaws. Now, on the picture above, am I seeing right? You have tape on the tip of the jaws?

Will


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## Mirage_Man (Mar 13, 2008)

wquiles said:


> Brian, which part # did you end up buying?
> 
> Will



This is the chuck from Enco and this adapter plate from J & L. But the only reason I got the adapter from J & L was because of the sale.


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## precisionworks (Mar 13, 2008)

> am I seeing right? You have tape on the tip of the jaws?


No tape, probably the reflection of the light in the photo.

I posted this on a machine shop bbs some time ago & caught hell for modifying a chuck with solid jaws (versus boring out soft jaws). But my chuck doesn't have a soft jaw option, and being able to grip consistently at the very tip of the jaws is really useful. If you work 8 hours a day in a production machine shop, running a lathe or a mill or a big drill, you tend to find shortcuts that help maximize your time.

Here's an article about a fixture that the same guy designed:

http://www.mmsonline.com/articles/0207rt3.html


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## Torque1st (Mar 14, 2008)

precisionworks said:


> An old time machinist showed me this trick, which involves boring a small recess in the end of the jaws on a 3 or 6 jaw chuck. Handy as pockets on jeans when you need to surface or thickness a spacer, and much faster than using the surface grinder. You cannot be real aggressive on the cuts, as there are only six tiny contact points on the work, except at the diameter at which the jaws were bored. Still very capable and something we used daily when I worked as a machinist.


Nice trick, we usually used a spud under the work to space the work out but we were limited on the thickness of the plate by the chamfer on the jaws. The size of the center hole also put a lower limit on the diameter we could handle with that method also.

I just may set up a set of soft jaws on my chucks that way for quick work. Although it will take a few minutes to change the jaws.


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## wquiles (Apr 1, 2008)

By the way, for anyone following this thread, I ended up returning the new Bison precision 3-jaw chuck and ordering a 6-jaw set-tru chuck instead 

Will


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