Chuck Run-out

You have to be careful on what you choose as a standard for roundness, straightness, or cylindricity. Hardened drive shafts, for instance have a relatively poor tolerance spec. for straightness, somewhere around .002"/ft. Drill rod also has a rather poor tolerance for straightness.

I have run across dowel pins with a bend as well. A dowel pin is usually used to align two parts that are in close proximity to each other. Diametric tolerance is important but straightness isn't that important. I would expect pin gages to be fairly good but I have run into pins that are bent. They are precision ground for a specific diameter and straightness isn't even specified.

Note that although a tolerance spec. is loose or not specified doesn't mean that a pin, rod, shaft,etc. isn't straight. There is never an intent to make a crooked part aqnd some are going to turn out well within our needs. Just measure before use.

Trust but verify!
 
ddickey said:
I had the three outer cap screws out. I could not separate the halves. DO I have to take out the cam lock pins also?
Click to expand...

I hope you get some suggestions for separating the back plate and chuck with out damaging the mating surfaces.
 
ddickey said:
I had the three outer cap screws out. I could not separate the halves. DO I have to take out the cam lock pins also?
Click to expand...

With the screws out you could try ligtly tapping the back plate with a soft face mallet, if that dosn't move it try attaching back to spindle and tapping chuck with soft mallet. Keep hold of the chuck to prevent falling damage.

Make sure theirs somthing protecting the ways like a piece of wood as it will just fall off at an inapropriate moment if you don't :)

Stuart
 
Okay I got it all apart, cleaned, lightly oiled and put back together. It wasn't to dirty but I think it was a good idea to clean it up. Thanks for all the help.
I turned a piece of 1 inch aluminum and run-out was .010". I'll check again once I get a precision ground dowel pin.
 
For those readers that follow you, it would help if you told us what you did to get the chuck apart.

Also, if you turned a piece without removing it then you should have near or zero runout unless the piece is really long. Can you post a pic of your set up?
 
I took the three outer and inner screws out. I had to put the chuck back onto the spindle. Gave it a few blows at an angle with the dead blow hammer and it came apart. Getting the scroll out wasn't bad but I had to use a punch to remove.
I must of made a mistake somewhere as I turned another piece and came out to <.001" run-out.IMG_20160909_160549221.jpg
 
ddickey said:
I took the three outer and inner screws out. I had to put the chuck back onto the spindle. Gave it a few blows at an angle with the dead blow hammer and it came apart. Getting the scroll out wasn't bad but I had to use a punch to remove.
I must of made a mistake somewhere as I turned another piece and came out to <.001" run-out.View attachment 135536
Click to expand...

Okay, three pinion retention screws and three body screws - thought you had some hybrid chuck or something.

Under a thou for a 3-jaw is pretty acceptable. I bet you could get it under that with a sharp HSS tool.
 
ddickey said:
I took the three outer and inner screws out. I had to put the chuck back onto the spindle. Gave it a few blows at an angle with the dead blow hammer and it came apart. Getting the scroll out wasn't bad but I had to use a punch to remove.
I must of made a mistake somewhere as I turned another piece and came out to <.001" run-out.View attachment 135536
Click to expand...
If you get .001 runout with a 3 jaw you are a lucky man and the envy of all,
 
All I did was turn down that 1" aluminum piece you see. Set up my test indicator and it doesn't quit make it to .001". It's .0005" per deviation I'm pretty sure.
I could be doing something wrong cause that does seem very slight for Chichuck.
 
ddickey said:
All I did was turn down that 1" aluminum piece you see. Set up my test indicator and it doesn't quit make it to .001". It's .0005" per deviation I'm pretty sure.
I could be doing something wrong cause that does seem very slight for Chichuck.
Click to expand...
I did not realize that you measured a turned part, these will always be within the spindles accuracy, the thread title is Chuck Runout. Indicating a turned part will tell you nothing about the chuck as it will always rotate the part at the spindle center.

Many people will tell you that you can not trust ground round parts for hobbyist accuracy, do yourself a favor and buy a 2" long hardened dowel pin say 1/2" diameter and put that in the chuck and indicate it. If you are truly obsessed buy a gauge pin as they do not cost much, one may buy a Go gauge at 1.0001 for a bit over $13.00 from Mcmaster-Carr. http://www.mcmaster.com/#gauge pins
 
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