Methods for parting off larger diameters

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Hukshawn

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i have a 3" aluminum part I need to part off the lathe. My 3/32" parting tool isn't gonna do it... I don't have a stationary band saw, I have a hand held band saw. On larger diameters it tends to wander and I don't have a whole lot of meat to play with to allow that wander and just face later...
Ideas?
 
Why won't your tool work? Is it an inserted tip tool with limited travel or some other issue? A 3/32" T- or P-type tool should make that cut. The only other real options are to hacksaw it and face it or flip the part, indicate it square and face off from the other end.
 
It's a parting blade in a qc tool holder. Last time I had more than 1 1/4" of blade sticking out there was a shocking amount of flex, and obviously chatter. The diameter of my part is 3.100" and that's in a shoulder from a 4.500" piece of stock. I'm just not comfortable with that much blade sticking out.

I might hack it off with the saw and do it from several directions to not give the blade a chance to deflect as much as if I were cutting right through. Then just face it. There should be enough material. I just have one shot at this...

Here's what I'm making. I was going to bore the hole after I parted it off to avoid having to drill out and bore a blind hole.
IMG_0187.JPG

I am making the piece backwards first. With the smaller diameter shoulder being cut first in the end of the stock. Then once that's finished and parted off, I will set up that shoulder in the jaws and start cutting the pulleys.
 
.... I have a hand held band saw. On larger diameters it tends to wander and I don't have a whole lot of meat to play with to allow that wander and just face later...
Ideas?
How about partially parting (grooving) the piece with your parting tool as far in as you feel comfortable and then finish with the bandsaw, giving it less time to wander during the cut?

Tom
 
That's an option for sure. I had done that before and didn't pay attention and the band saw made a horrible mess..
That would significantly reduce the cutting time as I can't get blades less than 20 tpi in that (Chinese) size saw.
 
Okay, I see. I wonder if you can part in part of the way and stop the lathe and slow the speed down a bit to complete the cut. If the lathe is tight and the parting tool is on center and perpendicular with the ways, a 3/32" blade should be able to make the cut. However, as you approach the inner third of the part the SFM picks up and that can cause issues; slowing down may allow you to complete the cut without under drama. Why not try it and if it fails, hacksaw the thing from there.
 
I haven't much choice. I will give it a try.
 
Okay, I see. I wonder if you can part in part of the way and stop the lathe and slow the speed down a bit to complete the cut. If the lathe is tight and the parting tool is on center and perpendicular with the ways, a 3/32" blade should be able to make the cut. However, as you approach the inner third of the part the SFM picks up and that can cause issues; slowing down may allow you to complete the cut without under drama. Why not try it and if it fails, hacksaw the thing from there.
Mike, SFM decreases with a smaller radius. I am sure you know that. Am I missing something?
i have a 3" aluminum part I need to part off the lathe. My 3/32" parting tool isn't gonna do it... I don't have a stationary band saw, I have a hand held band saw. On larger diameters it tends to wander and I don't have a whole lot of meat to play with to allow that wander and just face later...
Ideas?
I have parted off 3"+ steel with my 3/32" T shaped HSS parting tool in a BXA holder without problems. Aluminum should be much easier. Get the details correct: blade absolutely square to the work, cutting edge on center or very slightly below, carriage locked and everything tight, lower than normal speed (perhaps 300-400 RPM for your aluminum 3" job). Feed at a steady but not aggressive pace, try to keep the tool cutting continually if all keeps going well, you can use a cutting fluid like WD40 or kerosene to keep the aluminum from welding to the parting blade. If it starts going bad, just stop and go with a hacksaw or band saw. I do not power feed when parting off, l like to feel the cut in progress...
 
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