Lathe Runout

eodcoduto

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Aug 16, 2016
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Gentlemen,
I have a Clausing Colchester Master Mk1.5, built in 1966. I chucked up a 3/4" diameter endmill and put a dial indicator on the shaft and ended up with .003" of runout. This is a 50 year old lathe so I suppose that isn't too bad, but I would like to get it down to .001". The lathe has a Burnerd chuck with bolt on jaws (not sure what those are called). Any help is appreciated!
 
You first need to determine where the runout is coming from, it could be in the spindle, or the chuck, or possibly even in the end mill. First measure the spindle directly for runout and for bearing preload and possible looseness. I don't know what type spindle you have. Is the chuck a three jaw scroll chuck, a four jaw independent jaw, or something else?
 
My spindle is a L00, and I have a 3 and 4 jaw Bernerd chucks and a collet closer. I haven't use the collet closer but that might give me a better idea of how the bearings are doing.
 
I wanted to know which chuck you were using when you tested it. Three jaw chucks are not accurate, by design. .003"runout is actually pretty good for a three jaw chuck, though it can vary on the same chuck depending on work diameter, work stickout, and the condition of the jaws. Four jaw chucks can be dialed in by a competent machinist to near zero runout, but that number might change nearer and further from the chuck. An end mill can be whatever it is. You have left us with too many variables to answer your question. If you are trying to find the accuracy of your lathe, then measure your lathe, not a chuck or an end mill. Take off the chuck, and indicate the spindle nose for runout. Try deflecting the spindle nose and also the left and of the spindle using medium pressure sideways to the spindle while checking it to look for loose or worn bearings.
 
I just pulled the chuck off and checked the spindle. .0002" on the test indicator, and .003" with the end mill shaft in the 3 jaw. I used the end mill because it is the only thing I have that should be precision ground. I'm happy with the results, especially for a 50 year old machine.
 
I just pulled the chuck off and checked the spindle. .0002" on the test indicator, and .003" with the end mill shaft in the 3 jaw. I used the end mill because it is the only thing I have that should be precision ground. I'm happy with the results, especially for a 50 year old machine.
Sounds very good to me!
 
My spindle is a L00, and I have a 3 and 4 jaw Bernerd chucks and a collet closer. I haven't use the collet closer but that might give me a better idea of how the bearings are doing.

I just got the same lathe a week ago. Your taper for a 15" should be a ASA Loong taper L1. With a 2 inch (plus) spindle bore.
 
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