Advice Please

[jbolt]

A little more info I should have stated at the beginning, I sometimes have gaps from my brain to the outside world.

I have run a dial indicator on the 3 jaw chuck and on stock in the chuck, the chuck run true, it when I indicate the stock that I am getting the run out. The conclusion I drew from that was that the chuck body is running fine, it's the jaws and the scroll plate that are out. ( I was going to say out of tolerance but I don't know what the manufactures tolerances are).

Thoughts please

I would start by disassembling each chuck, give it a good cleaning and check for wear, burrs, damage etc. Address any burrs with a stone and then lube and reassemble. Check the run-out over a large range, i.e. 1/2" to 3" or more. Depending on condition, wear etc, it may give you different readings over the full range. While it is apart I would also check the run-out of the back plate when mounted to the spindle.

 

[eric.grulke.79]

I would start by disassembling each chuck, give it a good cleaning and check for wear, burrs, damage etc. Address any burrs with a stone and then lube and reassemble. Check the run-out over a large range, i.e. 1/2" to 3" or more. Depending on condition, wear etc, it may give you different readings over the full range. While it is apart I would also check the run-out of the back plate when mounted to the spindle.

I have had it apart and it is clean, no burrs, and there is no run out on the backplate, that is what is making me think the scroll plate and or jaw "threads" are/were poorly machined, this isn't a new phenomenon with this chuck, I'm simply fed up with it.

 

[jbolt]

I've found that that is critical if you are doing larger and longer stock which you want to fit through the spindle.

No reason to limit the full potential of the machine. Most of the 1660 class machines I have seen with D1-6 spindles have 2" or slightly over 2" bore so an 8" chuck would be fine. There some out there that have larger spindle bores.

However, having smaller than spindle bore is helpful when needing to hold small parts, as at least on my 4jaw the larger hole means the jaws don't close as small.

I've chucked a smaller chuck inside the larger and/or held a 5c collet block and run very slow rpm. Slow rpm required that that the job takes longer. And I don't know that a chuck inside a chuck is best practice.

Over time I think most of us end up with a range of chucks over time depending on the need.

I have a 4" 4-jaw that I regularly hold with my larger 8" 4-jaw when working on smaller parts. I never felt the the need to limit the speed.

On my previous lathe, a 13x24, the C5 chuck was my go-to chuck. On my current 1440 my 8" adjustable 3-jaw is the most used. I know a lot of guys that prefer to use the 4-jaw but it is hard to beat a good quality adjustable 3-jaw for repeatability when doing multiple parts. One of these days I will add an adjustable 6-jaw.

 

[eric.grulke.79]

No reason to limit the full potential of the machine. Most of the 1660 class machines I have seen with D1-6 spindles have 2" or slightly over 2" bore so an 8" chuck would be fine. There some out there that have larger spindle bores.



Over time I think most of us end up with a range of chucks over time depending on the need.

I have a 4" 4-jaw that I regularly hold with my larger 8" 4-jaw when working on smaller parts. I never felt the the need to limit the speed.

On my previous lathe, a 13x24, the C5 chuck was my go-to chuck. On my current 1440 my 8" adjustable 3-jaw is the most used. I know a lot of guys that prefer to use the 4-jaw but it is hard to beat a good quality adjustable 3-jaw for repeatability when doing multiple parts. One of these days I will add an adjustable 6-jaw.

I don't have an issue indicating stock in the 4 jaw, I just like the convenience of the 3 jaw and my current 4 jaw is limited to 700 rpm, as per the manufacturers instructions.

 

[jbolt]

I have had it apart and it is clean, no burrs, and there is no run out on the backplate, that is what is making me think the scroll plate and or jaw "threads" are/were poorly machined, this isn't a new phenomenon with this chuck, I'm simply fed up with it.

If the run-out is fairly consistent over a range then it could be a poorly machined or worn jaw/teeth. If the run-out is not consistent or moves around the chunk, occurs at different locations then the scroll could be suspect.

I put Gator chucks on my PM-1440GT. I know there has been some mixed reviews in the past but in the year plus I have used mine I have nothing but good things to say about them.

I have a friend who started with a Buck adjustable that had trouble holding parts. Parts would spin or move in the jaws. If I recall it was something to do with how the jaws were ground. He moved to Pratt Burnerd chucks. Very nice chucks but pricey.

I also have a Bison 5C that is very well made.

 

[eric.grulke.79]

If the run-out is fairly consistent over a range then it could be a poorly machined or worn jaw/teeth. If the run-out is not consistent or moves around the chunk, occurs at different locations then the scroll could be suspect.

I put Gator chucks on my PM-1440GT. I know there has been some mixed reviews in the past but in the year plus I have used mine I have nothing but good things to say about them.

I have a friend who started with a Buck adjustable that had trouble holding parts. Parts would spin or move in the jaws. If I recall it was something to do with how the jaws were ground. He moved to Pratt Burnerd chucks. Very nice chucks but pricey.

I also have a Bison 5C that is very well made.

We had the Bison chucks in school and never an issue with run out. If it is the scroll plate and/or jaw teeth, I suspect that there is little to do to fix that.

 

[joshua43214]

A little more info I should have stated at the beginning, I sometimes have gaps from my brain to the outside world.

I have run a dial indicator on the 3 jaw chuck and on stock in the chuck, the chuck run true, it when I indicate the stock that I am getting the run out. The conclusion I drew from that was that the chuck body is running fine, it's the jaws and the scroll plate that are out. ( I was going to say out of tolerance but I don't know what the manufactures tolerances are).

Thoughts please

You can still center the chuck, having the outside running true only effects the balance - mainly an issue at high speed, unless it is bad enough to hurt the bearings (has to be pretty bad to be more stressful than cutting steel).
I get the idea that you do not want to be limited to 700RPM, it is a good bet that you would see harmonic vibrations in the work if you had to set an 8" chuck 0.020" off center. So sounds like a replacement is in your future

Mounting a small chuck in a big chuck is an old pro trick (I'm not a pro). I've seen pics of multiple chucks mounted in huge chucks.
I do it with my little 4" 4jaw from time to time. I was going to make a D1-4 adapter for my rotary table, but it turned out to just be easier to toss the little chuck in my big chuck, then bolt the little chuck to the rotary table for 2nd ops.

 

[eric.grulke.79]

You can still center the chuck, having the outside running true only effects the balance - mainly an issue at high speed, unless it is bad enough to hurt the bearings (has to be pretty bad to be more stressful than cutting steel).
I get the idea that you do not want to be limited to 700RPM, it is a good bet that you would see harmonic vibrations in the work if you had to set an 8" chuck 0.020" off center. So sounds like a replacement is in your future

Mounting a small chuck in a big chuck is an old pro trick (I'm not a pro). I've seen pics of multiple chucks mounted in huge chucks.
I do it with my little 4" 4jaw from time to time. I was going to make a D1-4 adapter for my rotary table, but it turned out to just be easier to toss the little chuck in my big chuck, then bolt the little chuck to the rotary table for 2nd ops.

For the short time that I apprenticed, I had to turn down some 1 1/2" sq SS to run bearings on the each side, I had to mount a 10" 4jaw scroll onto the 3 jaw on the lathe, the 4 jaw was a plain back that the shop made a backing plate for mounting into the 3 jaw.


Sent from my iPhone using Tapatalk

 

[eric.grulke.79]

So I chucked up some different round stock, what I had really and here are the results,

2 1/2" round CRS
1" from chuck +.012" - .002"
12"from chuck +.043" - .000"

1 1/4" 4140
1" from chuck +.017" -.003"
12" from chuck +.031" -.000

1" TGP
1" from chuck +.018 -.002
12" from chuck +.031 -.005

Thoughts?

 

[Bob Korves]

That looks like jaw problems to me, Eric. If not that, then chuck to spindle issues. It might be worth grinding the jaws. Is it possible to turn the jaws around and test it?