Logan 820 Cross-slide collar

tmenyc

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Does the micrometer collar on my 820's cross-slide measures the tool bit movement or the amount of material being cut? Is it in thous? There's some slop in my old lathe and I'm trying to pin down how much I'm compensating for. I've looked through the original catalog and instruction manual but it doesn't say anywhere. Is the answer for the cross-slide the same for the compound?

Many thanks.
Tim
 

mmcmdl

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It's measuring both . Theorectically speaking , if your tool moves .050 , that should be the depth of cut . ( .100 on diameter ) You'll have some error due to spring and possibly slop , but it'll be close . .050 on the dial will most likely be .100 on diameter . Take a cut and measure and don't wait till your finish cut . :grin: Some lathes are in diameter , some in radius . Your compound would be in radius most likely .
 

francist

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You can check it easily enough using a simple dial indicator. Advance the screw to remove any backlash, zero an indicator against the tool, then advance the screw a set amount according to the micrometer dial collar. Compare that to what the indicator says and you have your answer.

-frank
 

TomKro

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I believe the smaller Logan lathes use 10 thread per inch cross feed screws, which means that 1 turn moves your tool 1/10 inch, so that material comes off the radius. You have to move your tool 1/2 as much to work your way down to your final desired size.

The smaller Logan's have dials that are quite small and tough to see. I resorted to using electrical tape to secure a sewing machine needle to act as a pointer. A bit crude, but it helps me. I'm sure other Logan users have done a lot better, short of replacing the dials.

TomKro
 

tmenyc

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thanks, guys -- appreciated.

Tim
 

tmenyc

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Well, as Francist suggested (and I certainly should’ve known to try; they don’t call us newbies for nothing), I put the indicator on it, and ten readings of 10 thou totaled .099, which is certainly close enough to 1:1, so that answers it.
Thanks!
Tim
 
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