4 Jaw Stand offs and the quest for concentric lathe work

[Janderso]

Hi all,
I am learning, all the time. I really thought I made these stand offs well. They are made out of tool steel and getto hardened.
I can adjust the depth simply by turning the tapered allen screws in or out based on the indicator reading. They lock with a brass set screw.
I failed to put the screws in a collet and face the mating surface. I was not successful in machining two perfectly concentric faces. I bored a piece of round stock, slid the part on the shaft and I could see lateral movement.
If I want to work on a hub, collar, pulley, etc. I need to have a way of holding the piece with something like a lathe mandrel.
I had in my mind these stand offs would allow me to surface/feature a part without a hole concentrically (is that a word?). I guess I could do the same on the mill.
Anyway, I'll try an end mandrel. The way the screw expands the mandrel to hold the part seems like it would not be consistent. I guess if the expansion is uniform? it will hold the part without worrying about lateral movement.

What are your thoughts on this method vs. turning between centers using an arbor?

learning every day.

 

[Grinderman]

Could you remove the chuck jaws and take a skim cut off of the 4 faces of the adjustment screws?

 

[pontiac428]

Don't you have a surface grinder, Jeff?

 

[Janderso]

Could you remove the chuck jaws and take a skim cut off of the 4 faces of the adjustment screws?

I’m thinking they would need to be screwed into an arbor of sorts? I don’t think they would be supported enough for a skim as is. Maybe, with light cuts?

 

[Janderso]

Don't you have a surface grinder, Jeff?

I sure do! Now your thinking!
Maybe screw them into a block that has been set up in the mill, drilled and tapped with care.
Good idea. I’m always looking for a Good excuse to fire up the B&S.

 

[Grinderman]

Joe Pi had a good video on making standoffs for a chuck. Not easily adjustable but simple.

 

[mickri]

I am trying to understand how these standoffs are supposed to work. As best as I can tell is that each screw is screwed in or out until they are all in the same plane when you check them with a DI. If that is the case then why can't you just face off the top of each screw in a 3 jaw chuck to make it flat? What am I missing?
And how much time will it take to dial these in each time you want to use them? Having several different heights of Joe Pi's standoffs seems like a better and quicker solution.

 

[davidpbest]

Adjustable Chuck Stops

Making adjustable chuck stops for 3-jaw and 4-jaw chucks. Click photos for descriptions

www.flickr.com

More info here: https://www.hobby-machinist.com/thr...stops-for-3-and-4-jaw-chucks-long-post.61766/

 

[C-Bag]

Joe Pi had a good video on making standoffs for a chuck. Not easily adjustable but simple.

Joe Pie to the rescue, thanks for posting that link Grinderman. I don’t have slot in either my 3jaw or 4jaw and this fixes the whole problem. Simple fixes for a simple guy.

 

[Janderso]

Having several different heights of Joe Pi's standoffs seems like a better and quicker solution.

I have several different length screws but yes, this is the best idea. I will acquire or fabricate a series of standoffs that are identical. No need to adjust.
Sometimes I can't see what's in front of my face. I think i got side tracked. Oxtools, Robin Renzetti and Joe Pi all made a version of this. They were adjustable so I assumed I could pull it off.
I'm also thinking the delrin is expanding at the chuck jaw position, therefore cutting deeper at those points.
I have a plan now. Thanks guys.