Looking to get a 6-jaw for my PM1236

coolidge said:
YES I did 20 minutes ago, from NEBT.
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ok, that is a new one to me. I thought I had all the machinery suppliers scoped out.

website? (Google sends me to the Nebraska Transport Company, which I am betting is not who you bought the chuck from!)
 
darkzero said:
Yes & more likely no. The jaws are much narrower than a 3-jaw chuck. Occasional use with 3-jaws may be fine but I never do this. Overtime you may get uneven wear vs the used & unused jaws.

IIRC .312" is listed as the min range on both the 6" & 8". When I need to work on diameters smaller & don't want to swap out chucks, I use collets in the chuck (if I can).


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This is exactly the same method I use if I just need to machine something smaller the the minimum closing diameter of my 6-jaw which is .312". I generally use my Gator 6-jaw because a lot of tubing that I machine. I do use the 3 and 4-jaws quite a lot as well but the 6-jaw usually resides on th lathe.

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mredburn said:
Are the collets pictured straight walled rather than tapered?
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DA collets are not tapered, they have straight sides but are stepped as they are designed for tool holding to be used in a collet chuck. They're similar to ER collets where the entire length of the collet grips the tool so they're not designed for holding something short.

I do use the collet holder on the mill but very rarely now. I have always used DA collets mostly for holding small work.

On the left is a DA180 collet, the smaller one is DA200 (3/8" max capacity).

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RCW said:
Probably a really dumb question that only a newbie would ask, but what is the advantage (or disadvantage?) to buying a chuck with an adapter plate rather than an integral D1-4 chuck?
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Well if you wanted to mount this chuck on another lathe that had a different mounting, D1-4 or D1-6 say you would only have to purchase the appropriate back plate. Lets say you upgraded to a bigger lathe and wanted to keep this chuck for it. I 'think' that when you machine the back plate on the lathe to fit that specific lathe its also more accurate. Where is darkzero?
 
RCW said:
Probably a really dumb question that only a newbie would ask, but what is the advantage (or disadvantage?) to buying a chuck with an adapter plate rather than an integral D1-4 chuck?
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"Set Tru" adaptor plate has 4 allen headed screws that allow you to adjust the precise position of the chuck to completely eliminate any runout.

A good three jaw chuck will have 0.0015" of runout. An average three jaw chuck will have 0.003". A lousy three jaw chuck will have 0.005-0.010". Doesn't sound like much, but if you flip the part you have held in a three piece chuck, and turn it down, you will end up with two ends that are not concentric.... and 0.003" is noticeable. Typically, when you turn something down in a three jaw, you don't flip it. You turn it to a diameter that will fit in a collet, and than use a 5C or 3J collet chuck to finish it off (which typically is a lot more accurate). Or you completely finish and part the piece without ever removing it from the three jaw.

The "set tru" concept gives you another alternative.
 
RCW said:
what is the advantage (or disadvantage?) to buying a chuck with an adapter plate rather than an integral D1-4 chuck?
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The way I see it is the only advantage an integral spindle mount chuck is less weight. Maybe there's other advantages but I can't think of any right now other than they would cost less. When you have an integral chuck you have to rely on the quality of the chuck for runout. Quality chucks aren't normally guaranteed by the manufacture to have less that .002" run out, on a cheap import chuck expect more but you can get lucky. You can play around with it clocking the pins but it may or may not be better & will vary from lathe to lathe.

Like tmarks stated, adjustable chucks (Set-Tru, Adjust-Tru, Setrite, etc) have set screws to allow you to dial in the chuck. The set screw mates on a boss on the backplate & is why one is usually needed for adjustable chucks. These chucks are usually guaranteed to have .0005"-.0002" TIR (there are limitations).

I prefer to have a chuck with a backplate. Even on plain back chucks, like with what I did with the China 3-jaw that cam with my lathe, I turned down the register on the backplate so there would be just a bit undersize than the chuck & I use it as a "tap-tru" to dial in the run out. Usually not recommended but for light & moderate use it would be fine. I don't use that chuck much anyway. And like coolidge stated, you could always use it on another lathe simply by changing the back plate.

Now my 4-jaw, I chose to buy an integral D1-4. Since it's bigger & heavier, this cuts down on the weight. Also gives you an area to better grip the chuck when moving it because of the way it's casted. It's an independent chuck so dialing in gets done at the jaws anyway.
 
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