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cuemaker
03-10-2011, 01:55 PM
I am trying to sell a Southbend I have to help finance a new mill...So a older gentleman and his son come over to look... They dont know anything about lathes except they dont know anything about lathes.. But they got some advice for a tool and die maker on what to look for...

So we talk about the lathe, I run it, answer question etc etc... The older gentleman sees my DTI and asks how that exactly works.. I explain... he asks me to set it up and show him..

So I put it on my 4 jaw chuck body... its a Starret DTI that is .001....

The run out on the chuck body is .001... as in it swings between the numbers on the dial of 29.5 and 30.5 ( I set it at the 30 on the dial)

He was mighty impressed... I am not sure if I am... Should I be?

jack3140
03-10-2011, 02:21 PM
well i am pretty darn good

Black_Moons
03-10-2011, 02:50 PM
Its pertty good, the chuck body does not need to be 0 runout, Especialy in a 4 jaw its just balance of the chuck. In a 3 jaw.. well, your 3 jaw like has more then 0.001" runout, So the 0.001 runout in the body (to backplate mounting perhapse?) might help or hurt your chuck runout.

The *face* of the chuck however should be basicly 0 runout. Especialy if your like me and like to push your cutoff tool holder against the chuck face to align it straight. (With the toolpost nut loose of course)

shadtree
03-10-2011, 05:58 PM
The *face* of the chuck however should be basicly 0 runout. Especialy if your like me and like to push your cutoff tool holder against the chuck face to align it straight. (With the toolpost nut loose of course)

LOL, I thought I was the only one that did that. :D

oddball racing
03-10-2011, 07:30 PM
LOL, I thought I was the only one that did that. :D
I though we all did that!................Is it in the tips!!???

Carld
03-10-2011, 08:44 PM
I indicated the face of my 3 and 4 jaw chucks and they were less than .001" runout so I use the face of the chuck to align the QC tool post. It's fast and as close as it needs to be.

As oddball said, many of us do that.

PeteF
03-10-2011, 10:35 PM
Take a look at the recent thread I started regarding my experiences with expected runout of a 3 jaw. At the time of writing it will be in the last few pages. From my understanding a chuck manufacturer doesn't normally guarantee any real concentricity of the circumference of the chuck body to the register, it serves no real purpose, so there's no reason to do so. However in reality I believe the way they're mounted and ground when manufactured they typically will be quite concentric where you're measuring. The face on the other hand is a different matter and should be square. Not so much for the toolpost ( and yes like others I square mine the same way), but more when mounting work pushed up hard again the chuck face, or when using spiders. The figure you are achieving will be determined by how accurately your chuck was made and then mounted. It's not really important what it is with a 4 jaw however.

Pete

Carld
03-11-2011, 08:24 AM
Actually Pete, it can serve a real purpose if the face of a chuck has "0" runout. There are many times that I use the face of the chuck so square things up in the jaws. I will use parallels against the face of the chuck and hold the work against the parallels and the chuck face as I tighten the jaws. It gets you a good starting point for very accurate work and if it only has to be within .001" the parallel trick works great.

I have taken a light truing cut on the face a chucks to get them as near "0" as posible without getting ridiculous about getting it "perfect".

Don't forget to take the parallels out or you may have to dig one out of your body as it gets slung out.

PeteF
03-11-2011, 09:32 AM
Correct. Hence why I said that the face of the chuck should be square to the axis of rotation. On the other hand having the CIRCUMFERENCE of the chuck body concentric serves no real useful purpose.

Pete

philbur
03-11-2011, 11:20 AM
Balance might be an issue if concentricity is poor.

Phil:)


On the other hand having the CIRCUMFERENCE of the chuck body concentric serves no real useful purpose.

Pete

Carld
03-11-2011, 12:30 PM
It would have to be way off to affect the balance.

It's nice to have the steps on the chuck jaws very accurate also. Today I am doing a job that requires me to use the steps to get the work straight. Fortunately the steps on my 3 and 4 jaw chucks are very near to "0" so all I have to do is push the work against the steps and tighten the jaws in the 3 jaw or push it into the 4 jaw and snug the jaws and then center it with a dial indicator radially.

Well, it's back to work, customer needs the job quick and it's about a 20+ hour job.