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

Hi Janderso,

This is my rear parting toolpost and the parting off blade that I use in it.
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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.

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I can easily part off 50 mm round mild steel bar at 800 rpm, with lubrication.
 
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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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 :)).
 
Matt, the only thing left that I can see is exactly what you suggest.
I’ll try it this weekend.
Thanks guys
 
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.
 
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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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.
 
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.
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In this picture, I just parted off a 38 mm piece.

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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 :)
 
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.
 
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.
 
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