Another Parting off Thread

If I were to start over in learning to part steel, I would experiment and practice on tubing or pipe rather than solid round stock.

I always hand feed on my 10 X 30 lathe.

I thought I saw some pretty high RPM values listed here. What would you guys recommend for parting 2” 1018? I have been using about 170 RPM.
 
Did you get to play with this some more? I'm improving on my tries with 12L14 1", and a mystery steel 1.25". I have a 1.25 SS bar that is clean, and as square as I can tell without getting out the DTI. My 3 biggest improvements were getting center height, squaring the blade, and minimizing stick out before parting. I'm using my "poor" quality parting blade to test with, it says China 1/16 HSS, and is a P ("T") type blade. I am still far from stellar, but there was no drama. I have room for improvement, it took .010 to face the 1.25 square after parting, I dropped the RPM in the mystery bar to 300, it just sounded better, and the cross feed was used at the slowest for now. This is a previous catastrophe, and today's effort on the 1.25. I didn't get the pictures before I cut, sorry.


 
Aukai said:
I am still far from stellar, but there was no drama. I have room for improvement, it took .010 to face the 1.25 square after parting, I dropped the RPM in the mystery bar to 300, it just sounded better, and the cross feed was used at the slowest for now.
Click to expand...

Parting is like landing an airplane. Any parting operation that ends with the part severed and tool intact is a good one.

Based on cutting speed of mild steel (80-100 sf/m), 300 rpm is at the upper end of the speed range for 1.25 dia. stock.
 
The "bow" in the cut-off usually indicates that your tool is not perpendicular to the work, or that the tool isn't sharp all the way across the cutting edge. Post a picture of the business end of your cutoff blade. In your other thread, you said you were feeding it oil - how did you do that?
 
China blade, p2N, and oil can. Photo quality is not good.




 
I had all sorts of parting problems when I first started. Got almost all of the same answers as above. All are correct. I use a Shars .093 T, 1/2" wide to cut 1018 up to 2" without trouble. Using it on 2-1/2" 6061 now. The tool MUST be perpendicular to the piece. It has no side clearance. Bring up the tool to the face and eyeball it with a light. Stickout, speed, tool height and lubing the groove is a must. All pointed out above.

The solution was in an old post. Some of the guys here I think were in on it. Good luck finding it, but there was a whole thread on this.
The tool must be ground to about 5 degrees off of vertical. Put your bit in the holder. use an angle protractor ruler with a level on it. Get 5 degrees back from plumb and draw a line. Grind to the line, straight across. Don't do a Joe Pi trick with a slight angle. He has years of experience to get just the right amount of angle to eliminate the leftover burr. It does work, by the way, just not for beginners. Adjust stickout to .060 past center and reset tool height to dead center.

Since I changed the angle, I now cut by eye and ear. If the chips are right, and there is no vibration or screaming, I don't pay that much attention to speed. Getting pretty good cutoffs using just hand feed.

If someone can find that old post, it just might solve the problem.

Chewy
 
I have not devoted any real time to this recently. I'm still reluctant after the trouble I've had. I did part off a piece of 3/8 cold rolled the other day though. I hand fed, when it started vibrating I pushed harder and it got better. the chips were terrible... looked like wood shavings, definitely not tight curls, I think they were too thin too curl. When I get some more time to play with it some more I will let you know. Thanks for the support so far!
 
Trying to learn by trying :)
Parallel can look close, but if it isn't on, the choir starts up. My eyes are not great, and I'm seeing that my compound zero isn't. I can actually see a film separation if I look real close if there is a touch of oil, and I can feel slight movement while I'm setting Parallel.
 
Aukai said:
Trying to learn by trying :)
Parallel can look close, but if it isn't on, the choir starts up. My eyes are not great, and I'm seeing that my compound zero isn't. I can actually see a film separation if I look real close if there is a touch of oil, and I can feel slight movement while I'm setting Parallel.
Click to expand...

I hope you mean "perpendicular" instead of parallel.
 
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