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

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Janderso

Jeff Anderson
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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?
 

craptain

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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
 

Technical Ted

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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
 

benmychree

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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.
 

Janderso

Jeff Anderson
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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.
 

Janderso

Jeff Anderson
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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)
 

Technical Ted

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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
 

mikey

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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.
 

Janderso

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"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. ""
 

mikey

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... 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.
 

BaronJ

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Hi Janderso,

This is my rear parting toolpost and the parting off blade that I use in it.
25062015-016.JPG
It fits into the rearmost slot on the cross slide. Held with a stud into a "T" nut.
The blade is held by two tapered bolts secured from the rear by nuts and washers.
It was done this way in order to be able to get as close to the chuck as possible. In this case 2 mm clearance.

25062015-012.JPG
I can easily part off 50 mm round mild steel bar at 800 rpm, with lubrication.
 

Janderso

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Baron,
I'm having a hard time picturing your set-up, compared to my lathe anyway. You made the tool?
I'll keep at it Mikey.
 
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mattthemuppet2

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spin slow, feed hard. If you're getting chatter you need to feed harder until the tool is producing chips that curl up into little rolls. If you're getting shavings then its not cutting. If it's still chattering then slow the lathe down. 1/4 of normal turning speed for that material and diameter is a good place to start. Leave as little stick out of both work from chuck and parting tool from holder as you can to get the job done. I part stuff all the time on my little Atlas 618. Only problems I have are with the belt slipping or with the tool wandering due to too much stick out (4" is probably pushing it a bit :)).
 

Janderso

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Matt, the only thing left that I can see is exactly what you suggest.
I’ll try it this weekend.
Thanks guys
 

turnitupper

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As Mr Muppet says "spin slow, feed hard ". I find squinting and waiting for the worst works best. A couple of thou below centre seems to work better on my Sieg C6 toy. A piece of soft timber levered on to the work piece from opposite the blade works wonders on occasions for one or two pieces but might become a real anal pain for a lot. I use an ordinary tapered HSS cut off blade as i am too lazy to set up my new insert tool. Another thing to consider (purely theoretical on my part) is the thermal expansion of the part and the blade whilst parting may cause binding . To counteract this I sometimes take a cut 70 to 80% of the blade width beside the first cut, as less than 50% seems to make the blade wander into the previous cut. As you are parting just over 1/2" this should not be needed:bonesrock:. Best of luck,
John.
 

Bob Korves

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Jeff, the Phase II BXA parting tool holder holds the tool at a 4 degree angle, not parallel with the cross slide. The blade grind angle needs to be increased by that amount to get the correct relief angle "at the work." Using Mikey's 7 degree relief angle at the work, that would be a 11 degree angle grind on the tool.

Also make sure that the tool post is rigidly mounted to the compound, the compound seats solidly to the cross slide, and that the cross slide gibs are snug enough. You need a rigidly supported tool to stop chatter. Unless I am actually using the compound slide (rare), I tighten the gib tight, so the crank will not turn. If you are using a "T" shaped parting tool, it helps to shim the narrow portion of the blade against the tool holder to help support it and stop it from "singing." The secret to happy parting is mostly maximum rigidity, in every part of the setup. Also make sure that there is adequate clearance between the top of the compound t-nut and the bottom of the tool post when it is tightened. If not, then the t-nut is not tightening in the compound slots. It is also worth making sure that the compound fits well to the top of the cross slide, with no possible rocking.

Basically, start at the bed ways and make sure everything is solid all the way to the parting tool cutting edge, and not just by wiggling them...
 
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Janderso

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Thanks bob.
My parting operation is not rigid enough based on the information I have received.
When I get some time i'll give it another go.
 

BaronJ

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Baron,
I'm having a hard time picturing your set-up, compared to my lathe anyway. You made the tool?
I'll keep at it Mikey.
Hi Mikey,

I made the tool holder, not the actual parting blade ! The blade was one that I acquired at some time.
17-09-2018-006.JPG
In this picture, I just parted off a 38 mm piece.

19-08-2018-004.JPG19-08-2018-005.JPG
These two pictures show the parting off tool holder mounted at the rear of the cross slide. Note the blade is mounted upside down.
The item in the chuck jaws in these pictures is a "Wax Chuck". So called because the workpiece is effectively glued to the flat surface
by shellac. Also know as a "Shellac Chuck".

Hope this helps :)
 

mattthemuppet2

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not sure if you mentioned material or not, but start off with plastic (eg. delrin), then try alu and then move onto steel. Each progressively less forgiving but should allow you to refine your technique with practice.
 

ericc

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I'd be really cautious. Any hint of rubbing or vibration means stop trying and either figure out what's going on or go use a hacksaw. Sometimes, "expert" advice can be counterproductive. When I was a member of TechShop, one of the DC's (dream consultants) sneered at me when he saw me having difficulty parting, and said, "you just really don't know what you're doing, do you?" This was really not helpful. What he should have said was, "is this the first time you are parting; you should check the tool to see if the previous user blew the tip off the end." When I figured this out, by myself, he shook his head when he saw me take it to the grinder, and threw his hands up in exasperation when he saw the tool start cutting beautiful smooth curls. Instead, he should have said, "thanks for fixing that tool; you sure figured that one out." That positive reinforcement would have been a really helpful teaching tool to get this lesson etched in my mind.
 

mattthemuppet2

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"Any hint of rubbing or vibration means stop trying and either figure out what's going on or go use a hacksaw."

what's happening when you get rubbing or chattering is that the tool is trying to tell you something. Not necessarily to stop, but to change speed, feed or DOC. In this case rubbing or chattering is the tool saying "slow the speed, increase the feed". You have to listen to your machine, it tells you alot of stuff!
 

Janderso

Jeff Anderson
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Eric, the world is full of people with low self esteem.
 
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