Chuck a chuck
#11
I was curious how much runout I would get if I chucked the OD of the dovetail jaws on a 4" chuck inside the dovetail jaws of a 5" chuck. The jaws are closed on the 4" and almost closed on the 5". I was very surprised that I couldn't see any runout and it measured less than 0.003 Inch on the first attempt. I moved the jaws to be directly over each other and the runout opened to 0.016+.


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#12
Did you check the run out of just the chuck first?  I would say that is pretty good numbers to me anyway
As of this time I am not teaching vets to turn. Also please do not send any items to me without prior notification.  Thank You Everyone.

It is always the right time, to do the right thing.
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#13
If I see the picture correctly, I think your gauge is not set up for proper reading at that angle if you are reading the surface runout. At around 45*, you may be reading as much as 50% less.
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#14
The dial indicator is a finger indicator or commonly referred to as a last word indicator.  The finger pivots at the end of the body and has a spherical end.  The short finger, <.5 inches, is close to parallel to the inside surface of the chuck adapter being indicated.  The position of the body and dial to the angle of the finger displacement is somewhat adjustable and therefore not important.  The indicator dial movement is limited to a little over revolution or about 0.011 inch.  In short, it is not a linear plunger dial indicator so the angle of the body and dial to the surface indicated is not important.
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#15
Arlin,

I did not indicate or measure the runout of the chucks when new.  I have had those two for about 3 years and they get plenty of use. The chuck bodies still run w/o visual runout.  To get any meaningful data, I would need to machine a ring to be chucked and indicate that ring.  The reason I was surprised with the test setup is considering all the variables that are stacked together, that they ran so close to true.  The only error was when one set of jaws is clamped directly over the jaws below and I could see a gap in the face of the jaws.  I did not investigate the reason why.  Time to get back to turning......

Joe
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#16
An interesting experiment, but there are so many sources of runout that combine to what you are measuring.  I can't figure out why that setup is relevant to runout.
Still Learning,

Allan Hill
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#17
Did you check the outside runout or outside?

Also were the jaws as tight as they can go?   I am thinking there is nothing really wrong since they are not real machinist lathe jaws but not sure.
As of this time I am not teaching vets to turn. Also please do not send any items to me without prior notification.  Thank You Everyone.

It is always the right time, to do the right thing.
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#18
(07-04-2017, 10:00 AM)Joe K1 Wrote: The dial indicator is a finger indicator or commonly referred to as a last word indicator.  The finger pivots at the end of the body and has a spherical end.  The short finger, <.5 inches, is close to parallel to the inside surface of the chuck adapter being indicated.  The position of the body and dial to the angle of the finger displacement is somewhat adjustable and therefore not important.  The indicator dial movement is limited to a little over revolution or about 0.011 inch.  In short, it is not a linear plunger dial indicator so the angle of the body and dial to the surface indicated is not important.

   I don't know a better way to describe what I mean, but this video will explain it. But it does matter how you are angled to the axis of the finger on the indicator.
 Again, the pic isn't clear, but the position of the finger to the work is important for a correct and accurate reading. I have made this mistake more than once.



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#19
Thanks for your concern regarding achieving accurate dimensional readings. I fully agree with the referenced video.
I thought I carefully worded my explanation that reflects the same thing, "the short finger, <.5 inches, is close to parallel to the inside surface of the chuck adapter indicated."

The dial indicator is a finger indicator or commonly referred to as a last word indicator. The finger pivots at the end of the body and has a spherical end. The short finger, <.5 inches, is close to parallel to the inside surface of the chuck adapter indicated. The position of the body and dial to the angle of the finger displacement is somewhat adjustable and therefore not important. The indicator dial movement is limited to a little over revolution or about 0.011 inch. In short, it is not a linear plunger dial indicator so the angle of the body and dial to the surface indicated is not important.
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#20
So you are reading the inside surface and not the face? That's what wasn't clear- perhaps I missed that.

It is still important to adjust the gauge body as close to perpendicular and parallel to the surface you are reading if you need to know exact measurements.

My gauge is very sensitive, and by moving it away from a perfect position, will read quite differently.
Probably more than what is needed for most readings at .00005" and small changes are quite noticeable.



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