# Atlas 10D runout? wobble



## jmac (Jun 19, 2012)

Hi, i'm very new to the lathe so i dont know very many term's or what parts are called

i've done a fair amount of research and printed off a manual ect which altho nice to have dont really help, i'm in need of experience/advice

So it a Atlas 10D made approx 1936-37 with timken bearings and i have alot of wobble/runout?

the part that the chuck screws onto seems ok with a readout of 1 in error but upto 41 out of the chuck

i have a 3 jaw and i think original Atlas 4 jaw both have pretty much the same error

Anybody know what the hell i'm talking about?


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## swatson144 (Jun 19, 2012)

Your back plate seems fine. Though the fit may be sub optimal. tighten the bolts only snug and do the indicator test. When yo find the high spot give it a wack with a soft hammer and see if it moves. If so you are on the mend

Chucks get worn over the years, and damaged by abuse. 3 jaws can improve substantially depending on which socket you tighten.

The 4 jaw will be fine with some soft shim like copper between the jaws and work piece, if one of the jaws is sprung. Usually it is no real bother since you dial it in anyway, but handy to have something easy to deform if the jaws are sprung out.

Steve


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## pdentrem (Jun 19, 2012)

3 jaw chucks can have differing amounts of runout depending upon the amount of wear and distortion to the scroll that moves the jaws inside the chuck. On a used chuck the scroll can be worn a fair bit or even damaged.
Most times the chuck will be marked with a 1 beside one of the socket holes for the chuck key. That is the socket that gives the least amount of runout on the test bar when the chuck was made or tested. You can do the same by placing the test bar in the chuck and reading the runout after loosening the tightening each socket at a time. Note it is only for the diameter that test bar you used. 

The 4 jaw can be dialed in by moving the right jaws until the part is centered.

If the round stock is perfect and you have more runout the further from the jaws you are then you have what is called bell mouthing. The jaws are worn more to the outside than inside. This can be fixed.

The backing plate is usually turned in place to minimize the runout prior to the chuck being mounted to it. The shoulder is cut to match the inside recess on the back of the chuck so that the chuck spins with minimal runout on the spindle.

You can make a true set chuck by cutting the shoulder a little smaller than the recess, thus allowing you to loosen the mounting bolts on the back is TINY LITTLE bit and softly tap the chuck while reading the runout, by tapping until the runout is gone or minimized.

Any other questions that we can help, just let us know.
Pierre


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