Bill M's Pm1340gt Setup

Confused. Once you chuck a piece of material and cut/true it, it no longer matters how the chuck is holding the piece.

Unless you guys are talking about how repeatable a chuck can re-grasp the same piece over and over?
 
wrmiller said:
Unless you guys are talking about how repeatable a chuck can re-grasp the same piece over and over
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This is the repeatability if rechucked, rotated, or the chuck removed/remounted or changed. I use an index mark on the spindle and my chucks, so at least I mount them back up in the same position (I do notice a difference). Chucks/backing plates and collets can have a bit of skew when holding material, so alignment is for the most part relative to work holding system you are using and the piece that is chucked up. My 5C collet chuck has a TIR of about 0.0002" at the nose, but different collets can be out quite a bit at 4-6".

It would be interesting to do some test passes on the stock, with it chucked at different rotated positions and compare the results.
Mark
 
Ah, got it. This is the main reason I have this massive PBA set-tru chuck. I don't bother with this for normal stuff, but when necessary I can re-chuck a piece and near zero it every time if called for (like a barrel or something).
 
wrmiller said:
Ah, got it. This is the main reason I have this massive PBA set-tru chuck. I don't bother with this for normal stuff, but when necessary I can re-chuck a piece and near zero it every time if called for (like a barrel or something).
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I'm like you Bill. 90% of the time though I don't actually use a "basic" 3 jaw scroll chuck. (Unless I'm just doing some super quick turning of something and don't really care about accuracy)
But instead of a set-tru, I use a 4 jaw independent chuck. I actually find it quicker and easier to indicate something in the 4 jaw independent chuck than a set-tru. I can usually get it to under 4 tenths in less than 2 minutes. This way I'm able to get high repeatable accuracy if I'm taking the part in and out of the chuck. I learned this technique from many professional machinists over the years, though I definitely don't clam to be one. From what I've seen and been told, most professional machinists use 4 jaw chucks exclusively. Matter of fact if you go on YouTube you will find videos of machinists engaged in competitions of who can dial-In the 4 jaw independent the fastest.
 
As I said earlier, I'm just weird I guess. I can dial in a 3-jaw set-tru faster than I can a four-jaw. But in all honesty I've only used a four-jaw a handful of times. I've dialed in a set-tru tens if not hundreds of times.

I do my non-roundie stuff almost exclusively on the mill. :)

And I also am no where near a machinist. I just play with their toys. :D
 
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Other ruminations: I know some folks almost exclusively use a four-jaw, but I have no desire to dial in every piece I chuck up. To me that's time I can better spend doing other things. Besides, this PBA once dialed in to a diameter will repeat much more accurately than any other 3-jaw I've ever owned. Even if the next piece is of a different diameter but within .5-1" or so of the piece dialed in.

But having said that, this chuck is probably a whole lot more, cost-wise, than most hobby/home machinists want to spend on a chuck to just play around in the garage. :)
 
The PBA chucks are surprisingly accurate and well made, and my take on the Set-Tru is you set it once and leave it as such. It is not really made to be tweaked every time you chuck something up. I have this on my 5C and PBA chuck, and agree that they consistently maintain better than a 0.0004" TIR with different stock chucked up. Makes for quick work. My main gripe with 4J independent is if you are doing a lot of repeat work, getting the stock in/out is a pain, and then readjusting. So I mostly use my 8" combo which does both scroll and independent, switching out stock repeats to around 0.002"or better. A quick tweak on the independent scrolls and you are dialed in in about 30 seconds. Like Bills large PBA, these are expensive chucks but worth it in my book as I plan on using it the rest of my life.
 
I'm on the same page Bill. I use my 6 jaw set true almost exclusively on the lathe. Takes 30 seconds to get a piece running under 0.0005, a bit more if I want it as true as the chuck/piece will allow. The 4 jaw gets used for odd shapes or if I want an off center cut.

I'm looking to upscale my 6 inch 6 jaw to an 8 inch 6 jaw to take full advantage of the PM1340. The 6 inch I have resided on my little Southbend 9 inch lathe for the last 15 years. Too many toys on my list and to little $ to get all of them. decisions, decisions.....


wrmiller said:
As I said earlier, I'm just weird I guess. I can dial in a 3-jaw set-tru faster than I can a four-jaw. But in all honesty I've only used a four-jaw a handful of times. I've dialed in a set-tru tens if not hundreds of times.

I do my non-roundie stuff almost exclusively on the mill. :)

And I also am no where near a machinist. I just play with their toys. :D
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I like the idea of a 6-jaw, I just don't know if I can justify another $1500 to get it. :(
 
Way to rich for my wallet. I'm looking at the Gator 8" EA Series 6-Jaw Adjustable Chuck, these can be had for ~$540

wrmiller said:
I like the idea of a 6-jaw, I just don't know if I can justify another $1500 to get it. :(
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