[How do I?] Lathe Question - Probably common but for a noobie like me...

Wow! Thanks to all for the excellent information, and especially to 12bolts for all the detail and photos. Phil, you are right that I am thinking about how I might do something similar to removing the compound.

The one point that hasn't been addressed here; while I'm sure that one needs to be creative on how to solve a great many setup situations, is there a book that I can use as a starting reference point?

Thanks again to all for the great input! :worship:

Charlie
 
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Now that's a clever bit engineering/improvising Phil. But you should explain to "Clevinski" Charlie how the dickens are you able to do that with that big yellow helmut on ???:biggrin::lmao: Had to !
dickr
 
12bolts said:
On older, and smaller lathes where wear has become pronounced, or cheaper modern lathes that may have "issues" it can be worthwhile eliminating as many points of introduced errors as possible.
Cheers Phil
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So... I'd have to eliminate myself? :huh: :biggrin:

I don't consider it "waste", I figure it to be drop offs that I will find a use for later. :p

-Ron
 
Moparfever said:
Now for the easy way. Put your stock in the chuck and tighten until it's snug, not too tight. Turn on the lathe at a very slow speed. Easy to do if you have a VFD, otherwise you may have to use the backgear. You'll see the runout on the end as it wobbles. Hold a piece of wood in between the toolholder and the end of the stock, and with the lathe turning slowly, move the toolpost in until the wood is rubbing the stock. Don't let it rub the very edge, but just back from the edge. Slowly continue the movement inward until the stock is "pushed" into running true. Stop the lathe and tighten the chuck. Now you can face the end. Sometimes when pushing the end into running true the chuck might loose it's grip. You just have to try it again using a different amount of pressure from the jaws.
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Huh... I would never have thought of that! Thanks!

Charlie
 
That is certainly a nice trick to remember for problem pieces. Generally simply kinda wiggling/rattling the piece as you slowly and lightly tighten the chuck will get stock about as straight as it is going to run. If it isn't straight enough rotate 120° and try again. Stock generally isn't perfect (unless you buy ground) and 3 jaw chucks aren't usually perfect so you can either have them compound the runout or partially cancel each other.

Copper shims aren't just for 4 jaws, or to prevent marking. Some chucks with a lot of error will run a good bit better with soft copper shims between the jaws and the stock. It gives that one high jaw something to deform a little and let the other 2 get where they belong. I use this when I need something at finished OD to run better than the .003" of my chuck but not needing it to run so true as to change to the 4 jaw. Not lazy just bad back and heavy chucks. :eek: Of course if the work isn't at finished OD it'll have 0 runout after finishing so no worries.

Steve
 
I can't read all these posts. I turn on the lathe to a slow RPM,and present a non cutting surface to the rotating piece. Move the cross slide in until your bar runs true,AND DO NOT go past the point where the bar runs true.or you will soon tear the piece out of the chuck,possibly damaging it. Takes just a few seconds to do this. The piece will run at true as the bar is round(it may be a bit out of round from extruding,rolling,etc.,but the bar will run nice and true for all practical purposes.
 
I am sorry but i have not introduced myself as yet, but i just wanted to put my 2 cents in. if you are unsure about the ability of your chuck to hold the material why not support the end of it with a steady rest?

PS I have been a hobby machinest for about 8 years and I specilize in turning good metal into scrap.
 
To centre up the work, rather than a piece of wood or similar use a roller bearing on a stick (OK, on a piece of cold-rolled held in the toolpost!) - that way the bearing tells you when there's contact (by rotating) and when it's constant contact (it keeps rotating all the way around the work!) - if you wind it in until the bearing rotates smoothly, *then back out slowly* it'll leave the work nicely centred within a thou" or two, good enough for Government work :)

Dave H. (the other one)
 
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