Atlas 618 Spindle and General Setup

J

JRT

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The runout on my lathe measures about .0005, or half a thousandth on the spindle just behind the chuck, which seems really acceptable. I am wondering if I have the spindle too tight though... Any suggestions on where I can get the instructions specifically for adjusting it properly? One member thought they recalled tightening it until spinning the chuck by hand would get about one revolution and then backing off the collar on the end of the spindle about two threads worth, which seems like too much. I have the manual (I think) but it has nothing in regards to this at all.

Also, my back gear doesn't seem to work... when I engage it, the cone pulley on the countershaft just slips under the belt and the belt doesn't move. I thought possibly the belt tension isn't enough but I do think the tension is good. I can't find the back gear use instructions either, not in my manual or from searching online.

Thanks in advance all! -John
 
Did you disengage the lock bolt in the bull gear behind the chuck? Yes, two turns of the collar would be WAY too much.
 
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IIRC 618s have babbet bearings or bronze sleeves.... how can you tighten them too much?
 
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benmychree said:
Did you disengage the lock bolt in the bull gear behind the chuck? Yes, two turns of the collar would be WAY too much.
Click to expand...
I did disengage that "pin".
 
it's loosen the collar two teeth worth of rotation. From memory (not ideal, admittedly) the spindle gear on a 618 is 32t, so that's 1/16th of a rotation (22.5 degrees?). Definitely not two threads showing. A more informal approach is to tighten up the spindle until you start to feel drag then back off the collar a smidge.
 
Basically hand-tight does it, then you tighten the collar setscrew. Happy bearings :cupcake:
 
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As I wrote this afternoon, the instructions for disassembly and assembly of the 618 headstock are in Downloads, which requires Donor status to access. Basically to preload the spindle bearings first you run the lathe for about 1/2 an hour to get it up to operating temperature. Then adjust the spindle end float to zero with a dial indicator with the capability of resolving +/- 0.001", Then you tighten the threaded collar two teeth on the 32 tooth gear on the left end of the spindle. Finally you lock down the two set screws in the collar, making certain first that each tapped hole has a lead or soft copper plug under the screw.

On your back gear problem, first make certain that the bull gear on the spindle has its Woodruff key installed and a set screw tightened down against it. With the back gears disengaged and the direct drive pin pulled out, and the the pulley and bushings properly lubricated, the pulley should turn freely on the spindle. With back gears engaged, it shouldn't. If they do, you may have to replace the cone pulley and gear. I don't have a 6" to look at and the parts manuals and part number indicate an assembly that's considered one part. Which it isn't on the larger machines. If necessary, loosen the set screw in the bull gear an slide the gear to the left and re-tighten the set screw. If that doesn't fix it, examine the back gears themselves.

Incidentally, the best of several 618 parts manuals in Downloads is probably the 1950 one.
 
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