Which position to tighten the three jaw chuck?

[jwmay]

Anyone ever do an actual test to see if there is a measurable difference in run out depending on which pinion was tightened and 1 vs all 3 tightened?

Probably. But not because it was useful.

If a person wants a 1” round part, one should start with a larger than 1” sized part to begin with. That ensures your part is on size and perfectly concentric in a 3 jaw. There’s simply no need to chase perfection in chucking on a first operation. Which is the only operation when a 3 jaw should be used.

People avoiding changing chucks have lots of reasons. None of them hold water. Get more chucks and stop playing with indicators. They’re meant to be in a drawer most of the time.

I see that sort of seems snarky. That’s not my intent. So please don’t take it that way. I’m just trying not to encourage time wasting.

 

[durableoreo]

I suppose it depends on the work. For small work in a 4" chuck, I have never given it a thought. But i could see this becoming important when I the stock gets heavy.

 

[Flyinfool]

Some of us are old and changing bigger chucks is not an easy thing.

For 99% of what I do the 3 jaw is accurate enough. Except for the current project of course that is in the 1%.

 

[Smithdoor]

Some of us are old and changing bigger chucks is not an easy thing.

For 99% of what I do the 3 jaw is accurate enough. Except for the current project of course that is in the 1%.

Just get 4 jaw to fit in 3 jaw chuck.
I would look weight of 4 jaw .

In November I replaced my old larger lathe with mini lathe for retirement.
I had chose between 10 pounds smashing my fingers or 16 pounds smashing my fingers. I when with 10 pounds. I will not do a project needing a larger 4 jaw and there always a face plate too.

Dave

 

[RJSakowski]

Anyone ever do an actual test to see if there is a measurable difference in run out depending on which pinion was tightened and 1 vs all 3 tightened?

I did for the OEM chuck on my Grizzly G0602 yesterday. There was no significant difference either in amount or direction of runout for either 3/4" or 1" pins.

 

[jwmay]

Some of us are old and changing bigger chucks is not an easy thing.

Maybe a swing away chuck crane could help. Rabler made a great device for changing his chucks. Mr. Pete made something as well, to ease the burden for exactly the reason you stated.

My old reason was that it took so long to dial in a 4 jaw. I’d bet that’s the most common reason.

 

[RJSakowski]

I did for the OEM chuck on my Grizzly G0602 yesterday. There was no significant difference either in amount or direction of runout for either 3/4" or 1" pins.

This evening I decide to see if rotating the jaws made a difference. Yesterday, I was experiencing runout almost three times what I normally expect to see so I pulled the chuck, took it apart and cleaned it. While the chuck was off, I checked runout on the face and shoulder of the spindle as well as the MT4 socket and all were on the order of a tenth.

I remounted the chuck and checked runout with the 3/4" pin and the 1" pin. The TIR for both was .005" which was still about double what I had seen in the past. I moved Jaw 3 to #1 position, jaw 2 to #3 position, and jaw 1 to #2 position. The maximum runout moved with the jaws and was now about.003" for both pins. I then moved Jaw 3 to #2 position, jaw 2 to #1 position, and jaw 1 to #3 position. and the maximum runout moved to about the same position where it was with the OEM jaw configuration and the TIR was .005" again.

I moved Jaw 3 back to #1 position, jaw 2 back to #3 position, and jaw 1 back to #2 position and the TIR was now .0002" for the 3/4" pin. I checked with the 1" pin and it was also .0002". This is amazingly accurate for A Grizzly three jaw.

With the aforementioned runout rotating along with the jaws, it tell me that the observed TIR isn't from the backplate or the chuck body but rather due to the scroll or one or more of the jaws. Since the measured runout was the same for both the 3/4" pin and the 1" pin, it isn't likely that the scroll is at fault since the two pins occupy different positions on the scroll. Why the TIR dropped from .003" to .0002" is a mystery. Perhaps there was a small chip in one jaw that I missed when I was cleaning. I should run through it again but given the low TIR, I am very reluctant to rotate the jaws. Let sleeping dogs lie!

 

[SWIGIN]

Anyone ever do an actual test to see if there is a measurable difference in run out depending on which pinion was tightened and 1 vs all 3 tightened?

Abom79 did when he installed a new chuck on his Victor lathe.

He wasn't getting the results that the chuck should have given and for him, tightening all three brought it in spec.

 

[SouthernChap]

People avoiding changing chucks have lots of reasons. None of them hold water.

I think you'll find my relentless, self-obstructive laziness, holds a great deal of water...

...in which, I regularly 'drown'.

 

[GrifterGuru]

People avoiding changing chucks have lots of reasons. None of them hold water.

Only time I ever "Change" chucks is based on needs at the time, but that does not mean it is not a pain.

Others may have issues that restrict lifting/holding/moving larger chucks, so stick to one chuck for most work holding needs.