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Hi everyone, I hope you are all safe and well!  I recently got my hand on a small Boley 8mm lathe as I would like to try to broaden my skill set.  I’m looking into getting a 3 jaw chick for it but what I’m finding all seem to be fairly expensive, like in the 300-400 USD range for used.  I’m just wondering if anyone out there would have a suggestion of a brand or maybe has hands on experience with something that is more affordable?  I won’t be using it a whole lot therefore something more affordable would be great.  

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They are so expensive because they are very useful and not enough of them were made. That said, I’d be loath to pay more than £150 for one. Have a look for ones made by Burnerd - they were often included in Pultra sets and will work with Boley threads. Another option for a cheap range of larger chucks is to get an ER chuck with an 8mm fitting. 

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Hi  worth a try.     Thanks for the information jdm.    Some times its cheaper to purchase a lathe  and use the chuck, some lathes go for around  150 ....170, chucks on their own are around 230/250  Burnerd  chucks about the same NOT cheap.

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16 hours ago, vinn3 said:

a 4 jaw chuck would be a better investment.

This might sound like a dumb question, but what is the practical difference, other than there being an additional jaw?

A other much cheaper part which I would recommend is a jacob’s chuck. I have fantastic ones by Bergeon and Jacob’s USA and they are so quick and easy for drilling. 

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I have one of the cheap Chinese chucks and I actually find it quite good. I still use collets for precision work but for large diameters I find it ok. One thing I do find is that sometimes my lathe struggles a bit to spin the extra mass of the Chuck. 

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Just now, vinn3 said:

CHUCKS;  jacob's  with 1/2 " x 20  thread US  will fit on some  unimat lathes.    a 3 jaw  chuck ( like a jacob's)) is suposed to be "dead center" and fast,     the  4 jaw chuck,   you set it to dead center or  off center for special jobs.  very veritile !  better choice at twice the price.   vin

 

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On 5/21/2020 at 3:40 PM, rodabod said:

This might sound like a dumb question, but what is the practical difference, other than there being an additional jaw?

A 3-jaw chuck is self-centring. All 3 jaws tighten in unison, so you are at the mercy of the build quality or wear in terms of how centred your workpiece will be. On a 4-jaw chuck, the jaws adjust independently. It takes longer to set up, but by using an accurate measuring instrument e.g. a dial gauge, you can centre exactly. You can also hold non-round workpieces, or set up purposely off-centre.

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1 hour ago, Klassiker said:

All 3 jaws tighten in unison, so you are at the mercy of the build quality or wear in terms of how centred your workpiece will be.

Not just the build quality, but the intrinsic limits of geometry and tolerances. Since the driving element a spiral groove that is common to all jaws, which must also work reversed, some design compromise must be taken so keep it acceptably smooth.
For example, on my Unimat 3 copy I have less than 0.01mm runout at the spindle chuck spindle register, but about 0.12mm with a precision 7mm round bar in the 3 jaws - which is the same as the Ebay example above.
There are ways to improve concentricity on  self-centering chucks, but in the end if precisions is needed either use collets, independant jaws, or turn between centers. There can be more ways also, as machining is full of ingenious methods.
All that being said, here we are talking about hobbyist / non-precisions chucks only. I'm sure that watchmaker's and and professional machines chucks have a different precision class. 

1 hour ago, Klassiker said:

On a 4-jaw chuck, the jaws adjust independently.

Not all 4 jaws chucks are of the independant type, and not all sellers do specify. Look for square sockets on the body in line with the center of all jaws. Below an self-centering 4 jaws chuck, again for the Unimat 3. These are mostly used for woodwork where high precision is not important, but you need to grab square section parts often. SAN-OU-Lathe-Chuck-50Mm-Mini-4-Jaw-Rever

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I’m not sure that I could be bothered with setting up a 4-jaw every time I wanted to do something simple like mounting a drill bit. My 3-jaw chuck is not for extremely accurate work. I’d like to measure it though. 

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13 hours ago, rodabod said:

I’m not sure that I could be bothered with setting up a 4-jaw every time I wanted to do something simple like mounting a drill bit. 

Nobody said that you have to use independent jaws all the time. Each machining tool has a purpose, and similar tools can overlap with another for certain tasks.

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Agreed. But I don’t think a 4-jaw is something I happen to need for my watchmaking lathe. Vinn says “4 jaw is best” but not for my needs. I’m not drilling main plate holes or anything like that.... I can’t think when I would have benefited from one. 
 

That said, I have used a 4-jaw a few times when making some tools on the larger clockmakers lathe. 

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9 hours ago, rodabod said:

Agreed. But I don’t think a 4-jaw is something I happen to need for my watchmaking lathe.

The issue with this topic is that it was started about watchmaker's lathing, then quickly migrated to general (hobby) machining. Similar but different  subjects, it's good to know a it of both.  

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Perhaps it did migrate, but someone initially stated that 4-jaws would be better, without referencing hobby machining.

I think there is a reason why self-centring 3-jaw chucks are the usual choice for watchmaking. I rarely do any eccentric turning, but I do have a faceplate which I can use.

Back to the original post: I can recommend getting a Burnerd or similar quality 3-jaw (German, Swiss, English, American). The Sherline chuck which jdrichard describes sounds promising too.

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6 hours ago, rodabod said:

Perhaps it did migrate, but someone initially stated that 4-jaws would be better, without referencing hobby machining.

Right. But we know well that our long time member vinn3 here is more familiar with machining that watchmaking :-) 

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Wow, thanks everyone, there's a whole lot of awesome information happening here!  This went a whole lot deeper that I thought it would.  I think a 3 jaw is still the most fitting for what I'm looking to do.  jdrichard, great video!  What you have there is exactly what I would be looking for and after looking into it those pieces are way more affordable than what I have been finding on ebay. 

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I would like to try my hand at doing some different types of case finishes (circular brushing, radial lines of sunburst finishes etc.), and I,ve seen these finishes done on small lathes with the 3 jaw and the results looked quite good.   Would the extra steps in setting up the 4 jaw be evident in the results that I would get?

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8 hours ago, jdm said:

Right. But we know well that our long time member vinn3 here is more familiar with machining that watchmaking :-) 

     if you are new to running a lathe,  use a 3 jaw,  jacobs' and collets.  most nubies are afrade of a  4 jaw because it takes much more time to  get it "on center".  with some experience,  a 4 jaw can be put on center in15 seconds.

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