Taking it to the final size

"Depending on what Im working with material wise, I will set the compound over to 45 degree,s and feed into the cut with the compound rather than the crosslide for the last few thousandths."




I usually do it this way, but feeding straight in with the cross slide does as good a job.....on a lathe that you are comfortable with. Experimenting with different tool angles will get you there fast.

Chuck up a piece, and start experimenting with the best feeds and speeds for the kind of tolerances, and finishes; you want.

Seems I always remembered more, due to my tests; instead of what I was being told. wink wink..nudge nudge.
:whistle:

 
I do use the Tony Well's aproach most of the time, gets me "right on" or most of the time "OH Shoot"...
Wish I had flood coolant but I usually coat the surface with a flim of cutting oil for that "last past", most of the time I get it right on.

On smaller lathes like most of us use, and using carbide tooling, keep the edge lightly honed for finish cuts. On carbide tooling honed edge means "break the cutting edge by x amount", you don't usually cut with a razor sharp edge in carbide. The more the edge is honed, the more you have to take in depth of cut to get it to actually cut. If you are using insert tooling use a lightly honed positive edge for finish cutting. If high speed steel, hone that edge to near razor sharp edge, totally the opposite of that of carbide.

On more ridigit heavier machines, you can generally hold size without difficulty with any carbide tooling provided the lathe is in good shape. Most of us are using vintage lathes in varying degrees of conditions so we will encounter problems holding tolerances. If youre like me you have various grits of emery cloth and a collection of files that aid us in holding tolerances as needed.

I know many will disagree with me on that, that's ok, this is how I learned. I would love to hear from others on this subject so we can have many thoughts on "taking it to final size".
 
Ken, you won't get any disagreement from me. On the old Monarch, I can't quite use the procedure I outlines above, but then, that's one reason I have the two lathes. Don't get me wrong, I can hit tenths on the Monarch too, mostly the same method, but there isn't the level of confidence there that is on the newer lathe, which by the way is an Acer. Pretty fair lathe, I think.

I try not to do the finicky work on the Monarch, unless the Acer has a setup I don't want to disturb. It's capable, and surprisingly repeatable for a lathe of its age. In reality, most of the work I do doesn't call for tenths tolerance performance. And the Monarch does just fine holding 0.002 for 'O' rings and the like. It's a pretty tight machine. One difference in the tow is probably the gear/bearing condition. The Acer will cut a finish that passes without much ir any polishing. I generally don't like papering on it anyway, but the Monarch just isn't as slick, so I do use paper. I prefer to use a flat file to back up the paper rather than just wrap it. In fact, this may be a good time to point out the danger of just throwing a strip of abrasive cloth around a spinning shaft. It will tend to be pulled in the direction of rotation, and given enough slack, can come all the way around and pinch itself up and snatch it right out of your hands, if your fortunate. Always be ready to let go of the paper if you insist on handling polishing like this. You can't win that wrestling match. I think most anyone who has spent time polishing shafting has had to give the paper to the lathe. I've been cut near to the bone by the edge of the abrasive cloth. Kind of painful, and makes you more cautious. And it should go without saying that wrapping paper around your finger to polish an ID is very, very risky. It can be very hard on the health of the knuckle joint of that finger. I keep a couple of "fingers" in the box for that when needed. One is simply a broomstick with a slot sawed into one end that I can wrap some cloth around and stick in the bore. Smaller than that, I have a couple of pieces of leftover Delrin set up the same way. For smaller yet ID's, where you can't get much pressure on the "stick", I use what most machinists around here call a butterfly. It's a 1/4" steel rod sawed to accept the cloth, and fit in an air motor. On this tool, the spindle doesn't even need to be spinning. Plus this can be used to deburr drilled/reamed/bored, etc. holes in nearly any part.
 
Tony

Very good tips about the use of sand paper on both OD and ID. Allways good to point out the dangers as well. Using files have there own danger too.

Lots of great infro guys
Keep it coming
 
Pauls got it, use the compound, everyone has their own method mine is always using my thread stop,
actually I never take it off. And as said compound swung over and it things are getting warm, go get
a cold one, when cooled then take that final whisker cut.
 
You'll normally get a better, more precise final cut by leaving more stock than by sneaking up on the final dimension a few thousandths at a time. I generally rough to within .010", move in .005" and take just enough of a cut to measure, then take the rest to full depth. The full .010" finish cut puts a little more load on the tool and produces better results. Other things to do that will help in holding tight tolerances is use high speed steel instead of carbide, select the best machining steel possible for the part (medium carbon or leaded steels), and use cutting fluid or oil.

Tom
 
HSS, or Carbide?
I know some of the members here will use Carbide. I tend to sneak up on the final cut. Carbide does like a fairly deep cut, and if you dont, it doesnt give a nice surface finish, for me anyway.

Im used to using HSS for finishing up the job. Ive allways had better luck, and surface finishes by using HSS, with a sharpened and honed edge. I guess if I was willing to take a deeper cut on the final pass, carbide would work for me too.

I have stayed with the HSS to do the last few passes because at least when Im taking a few fuzz cuts at the end, my errors are smaller than when I take a bigger bite at the end with carbide.

Right, wrong , or other wise, thats just how I do it. I say, if what you do works, no sense in changing your methods.
 
my small chinese lathe will flex so .005 may be .003 or .004
I try to make the final pass with tool steel not carbide
and if fitting to a bearing or needing exact fit i have a fine stone tool post grinder I made from a hf saw blade sharpener that takes very fine cuts.
I have tried the files and sandpaper and I prefer to put on the grinder
steve

Hello Steve

Can we have a picture of Your homemade tool post grinder?.I need one
 
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