13" South Bend with single lever gear box=Parting Vibration

Janderso

Jeff Anderson
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Mar 26, 2018
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Hi gang,
I read South Bend's manual on parting and lathe/tool set-up.
I watched a few videos on parting on the lathe.
I have the Aloris style tool holder (Phase 2 BXA)
The check list:
90 degrees,
Choke up with the parting tool
Sharp blade
tight gibs
close to the chuck
compound and cross slide centered as much as possible for stability
Spindle bearings are within tolerance (checked as shown in keep your lathe in trim by South Bend)
Spindle End Play is within spec.
Level the lathe

The only thing I have not done is "Bolt/Secure lathe to the floor"
I have tried the T shaped parting tool-Mcmaster Carr
I have the regular HSS blade type parting tool

You guys with older South Bends may or may not have a tough time parting without excessive vibration.
Any thing I am missing?
 
Sounds like you are starting out correctly. But....
What material? Lubricant? Height of the tool? Speed? Feed?
These are just a few more variables to check and/or experiment with.
I often have issues with parting off myself but one of the above usually fixes it.

Sent from my SM-G930T using Tapatalk
 
I've got a 15" and 13" SB and when I'm parting steel using a chuck on anything over I'd say 1" in diameter I get chatter if running at a higher speed. I have to use a heavier feed than I like to get the chatter to stop. The only way I've resolved it is to slow the spindle speed down by putting it in back gear (or slowing my VFD way down).

Either that, or I'll take it out and cut the part off in my bandsaw.

I never seem to get chatter when using a collet on either machine. Also, grinding your parting tool with too much clearance can cause chatter. Limiting it to 5 degrees for steel works for me.

Ted
 
Parting and chatter go together like the proverbial horse and carriage! I have troubles with chatter on my nearly unworn 9" Monarch, especially jamming up due to the tool angling sideways towards the chuck due to the offset of the Aloris type QC; is I slide it to the right so that the center of the tool is right of the cross slide edge, it helps, but no cure. Low cutting speed helps, and a lubricant such as TapMagic helps. The tool should be right on center, with a minimum of clearance, as stated above.
An old friend, a machinist of long tooth, told me, for the beginner, threading is difficult, but with practice, gets better, but parting NEVER gets better ---- He was pretty much correct; parting is always problematic.
 
Sounds like you are starting out correctly. But....
What material? Lubricant? Height of the tool? Speed? Feed?
These are just a few more variables to check and/or experiment with.
I often have issues with parting off myself but one of the above usually fixes it.

Sent from my SM-G930T using Tapatalk

Oh, sorry. 2.5" OD, cold roll steel. Bored out to 1.4" ID.
Seed, slow, not back gears-I did not check. I did try a higher speed-no help. Yes perfectly centered. Hand fed? I tried slower-faster. I used tap fluid, 20wt. non-detergent= no change.
 
Thank you Ted and John.
I'll try back gears. The angle is probably over 5%. I put a slight angle when grinding using the 8" wheel as my clearance. I'll close it up.
Would mounting on rubber feet help?
I have it on 5/8 studs on concrete=level. Probably not anymore with the chatter.
I'll try a collet too when I can. I have a blind ER40 chuck I rigged up with a home made draw bar. (It's a MT4 -ER40 chuck)
 
Oh, sorry. 2.5" OD, cold roll steel. Bored out to 1.4" ID.

If I was doing this in one of my lathes I would take the piece out and cut it off in either my horizontal or vertical band saw (depending on how long the stock and work piece are).

I don't think you'll win the battle in the lathe, but you might learn how to break a parting tool :( Ask me how I know...

Ted
 
I'm not so sure the relief angle has much to do with this. I've used a 7 degree relief angle for over 25 years and have had no issues parting. If you are exactly on center height, the tool is vertical and is perpendicular to the work then any chatter has to be due to movement in your set up somewhere.

I'm going to guess that the front of the compound (the end with the hand wheel) is lifting as you engage in the cut. You can rule this out by putting a jack under the parting tool to support it. If it parts well then you have your answer. You can also try orienting the compound so it parallels the ways; this reduces the cantilevering you have when the compound is at 29 degrees. I've seen this work on another SB13.

I have an Emco Super 11 CD lathe and it parts without issues with P-type blades or inserted carbide tooling at near turning speeds. Its only an 11" lathe but is very rigid for its size and everything is tight. In contrast, my little Sherline chattered when parting butter from the front of the work but it will part almost anything when parting from the rear, at quite high speeds. I believe this works because the upward cutting forces when parting at the rear are transferred downward at the rear of the parting tool holder, thereby taking up any play in the cross slide assembly. I've parted 2" OD steel at 1200 rpm on that little lathe so I know it works.
 
"You can also try orienting the compound so it parallels the ways; this reduces the cantilevering you have when the compound is at 29 degrees. I've seen this work on another SB13. "

I had the compound 90 degrees to the ways. When I set up this parting procedure it was my second time with the same cut/material.
After I went to school on line one of the suggestions was to do what you suggest.
I will try to support the tool but I only had 3/4" hanging out.
Maybe it can't be done. I just don't like to quit anything!
Band saw? I have three of them, and a parting tool.
Maybe I should start off with a smaller ID to gain confidence.

John said it, "An old friend, a machinist of long tooth, told me, for the beginner, threading is difficult, but with practice, gets better, but parting NEVER gets better ---- He was pretty much correct; parting is always problematic. ""
 
... parting is always problematic.

Maybe, but it shouldn't be. I hope you can sort this out because it should be a routine procedure that is simple and easy to do. Using a saw and having to face everything gets old really fast. You should also be able to use your parting tools to make grooves, thread reliefs, design features and so on. If you can't part with the lathe then that is a big deal.
 
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