How to test TIR when you don't have a gauge pin?

All my dowel pins are 4140 with chamfered ends. Those I use for measuring runout are 4” long. I have a number of different diameters. 1/4”, 3/8”, 1/2”, 5/8”, 3/4”, and 1”.
 
koenbro said:
I removed the chuck and checked the spindle nose which was within 0.0001". The replaced the chuck without a collet/nut and noticed the runout. I futzed with the 4 adjustment screws until I dialed it down to about 0.0001". Problem solved.

This was an incredibly useful learning exercise. Thank you for walking me along; also grateful @qualitymachinetools for the documentation on the PM website.

Can't believe I am the only beginner here, hope this will help others. Here is the process and the results:


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Looks good! Now that you have the process down, dial in the part/pin while it's clamped in the collet. That will account for any stacking error.
 
woodchucker said:
sorry, but I don't like the pins you are using. 2 things I have issues with.
1, the weldon cut out is on the edge of the collet
2, the pin is not long enough, ER collets need a deep take, and you are just shy of what I would call a proper bite.

so the 2 combine to give me no confidence in your setup.

next, ER collets are a little finicky. I find that you must clean the taper out with your finger to make sure its clean, and the collet.
Then when installing them, I like to spin the part / collet while just touching, to make sure it feels right, if it loosens, then tightens, go back to the loose... so it can pull it in further.
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Agree, one needs a pin in the 3-plus inch length range for proper collet engagement plus enough stick-out to measure off it. I will turn down some tool steel pin, part it off and use that in the future as my very own reference.
 
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Firstram said:
You loosen the 3 bolts holding the chuck to the back plate, then lightly snug them back up. The 4 screws around the perimeter are used to dial the part in. It's just like dialing in a 4 jaw chuck except you don't crank down on the adjustment screws. It's a finesse thing, snug is good! Once you're happy with the runout, tighten the 3 mounting bolts a little more. They don't need to be over tightened either.

You may as well pull the chuck off the lathe and disassemble it to make sure everything is clean before you start. Give the mating surfaces a light coat of oil before reassembly!
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By the way this ^ is how it’s done. Just to acknowledge and thank you for the advice.


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