# Cutoff Tool



## Mork (Feb 20, 2016)

Here's a tool post I made for my Logan 200 lathe. The AXA post I have has the capacity for a 1/2" cutoff blade and I was hoping a 3/4" blade would be more rigid. The post works but really no better than the 1/2 blade on the AXA post. Does anyone have any suggestions for as to how to stop a tremendous amount of chatter? I've tried high speed and the slowest speeds. The slowest is by far the best but still not great. I also checked the bearing in my head stock...  as near as I can tell I have about .001 slop in the bearing which doesn't seem excessive to me. 

I suspect I'm expecting a bit to much from a small lathe. The compound is nowhere near as solid and other lathes and the 1.5" head stock probably flexes under load. Still I'm hoping somebody has a good suggestion as to how to improve the chatter I'm getting.  Thanks.


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## master of none (Feb 20, 2016)

Hi,did you try locking down the compound?


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## ebgb68 (Feb 20, 2016)

Just a guess from a newbie does the taller blade adjust properly to center ?

Sent from my SAMSUNG-SM-G900A using Tapatalk


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## Wreck™Wreck (Feb 20, 2016)

This will probably be  beyond your targeted budget but an insert parting tool works a charm and if you have a problem it does not ruin the entire holder, that being said I have crashed more parting tools then turning tools as they are easily broken (-:
Have had excellent performance with these tools
http://www.kyoceramicrotools.com/indexable/pdf/Small_Tools_Catalog_Section_H_Cut-Off.pdf


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## Bill C. (Feb 20, 2016)

Mork said:


> Here's a tool post I made for my Logan 200 lathe. The AXA post I have has the capacity for a 1/2" cutoff blade and I was hoping a 3/4" blade would be more rigid. The post works but really no better than the 1/2 blade on the AXA post. Does anyone have any suggestions for as to how to stop a tremendous amount of chatter? I've tried high speed and the slowest speeds. The slowest is by far the best but still not great. I also checked the bearing in my head stock...  as near as I can tell I have about .001 slop in the bearing which doesn't seem excessive to me.
> 
> I suspect I'm expecting a bit to much from a small lathe. The compound is nowhere near as solid and other lathes and the 1.5" head stock probably flexes under load. Still I'm hoping somebody has a good suggestion as to how to improve the chatter I'm getting.  Thanks.
> 
> ...



Nice job


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## Chipper5783 (Feb 20, 2016)

I agree with Wreck.  I struggled with parting off for years.  The insert style parting tool made the difference for me - now parting is routine.


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## mattthemuppet2 (Feb 20, 2016)

the only times I've had chatter parting on my 618 is when I've had the work unsupported a long way out of the chuck. As long as the carriage is locked, the blade perpendicular to the piece and on center, plenty of cutting oil and a "groove widening cut" on deeper cuts, it's been fine. Run slow and feed hard - you should get nice curling up chips. Also check out the P1 and P1N blades, I find that they cut very nicely.

Also, those cemented carbide bits typically need sharpening out of the box. A bit of a touch up with a diamond disk and hone would also probably make a world of difference.


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## Mork (Feb 20, 2016)

Excellent feedback. Thanks!

I've never tried locking the carriage which now that I think about it makes a lot of sense. This will be the first thing I try. I'm sure the parting inserts are much better just like any insert but they are high priced. I may eventually splurge and give them a try. Thanks all for the advice. Oh and yes, the cutting edge is dead center, I've used a lot of oil and yes I broke the cemented insert off ( 

So far, the t shaped HSS blades have worked the best for me.


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## mattthemuppet2 (Feb 20, 2016)

I haven't heard of a single person who's actually liked those cemented carbide parting tools, although I guess they might be useful on very hard steels. Personally I've found cemented carbide bits to be a PITA on my limber lathe; chipped or shattered 4 in a row once. Now I just keep them for really tough or abrasive stuff (cast iron) or to do some high speed facing.


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## Wreck™Wreck (Feb 20, 2016)

mattthemuppet said:


> I haven't heard of a single person who's actually liked those cemented carbide parting tools, although I guess they might be useful on very hard steels. Personally I've found cemented carbide bits to be a PITA on my limber lathe; chipped or shattered 4 in a row once. Now I just keep them for really tough or abrasive stuff (cast iron) or to do some high speed facing.



All carbide tooling is cemented, I believe you mean cemented carbide brazed to steel blanks, this type of tool has never worked well for me and I will not use them unless it is a dire emergency.


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## mattthemuppet2 (Feb 20, 2016)

bah, yes, yes, chunks of cemented carbide brazed onto steel shanks.


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## Wreck™Wreck (Feb 21, 2016)

Upon reading the Kyocera  parting tool literature that I posted above a few things pique my interest. I have never read the booklets that come with the tools that I use because I am lazy and they are not my tools.

They advise setting the tool above the center line , I suspect that this is to account for a certain amount of tool movement even if you are running the coolest  Swiss lathe.


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## BGHansen (Feb 21, 2016)

No experience with cemented carbide, but I've had very good results with both the ISCAR's style GTN3/4 replaceable carbide inserts and 5/8" wide HSS cut off blades.  Key things are getting the most rigid set up possible and a sharp edge on the HSS blade (with tapered sides).  I always follow Tom's Techniques tip of touching up the HSS blade on the grinder prior to cutting.

Bruce

edit:  5/8" wide blade is 5/8" tall x 1/8" wide x 4-5" long.


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## Mork (Feb 21, 2016)

I think above centerline might also have to do with the way the inserts are ground. The 1/2" AXA holder I have holds the blade at an angle which has the same effect as running above center. I suspect this helps in two areas, first it changing the pressure angle on the compound (although not a much) and second it adds rake to the top of the tool without grinding...  although the grind angle on the front of the blade needs to be more extreme. I suspect this is why new blades come with opposing ends sharpened at different angles, one for a level tool holder and one that holds the blade at an angle.


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## brino (Feb 21, 2016)

Hi Mork,

Parting is probably the one operation that generates the most grief and discussion. It looks so easy and fantastic when it works well that it seems like a "no brainer", however many people have problems getting to the point of it working well. I sure did.

Personally, for me, the two suggestions that helped the most were:
1) use a wider parting tool. This seemed backwards to me; I figured the wider tool would mean more force trying to flex everything, but I now believe that the wider tool is simply more stiff 
2) remove any looseness/slack: lock the carriage, top slide, anything you do not need for this operation. (Same on the mill; if you get chatter lock the gibs for the feed directions you are not currently using!)

There are many great suggestions in these two threads:
http://www.hobby-machinist.com/threads/parting-for-idiots.32938/
http://hobby-machinist.com/threads/parting-difficulty.35356/

-brino


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## Mork (Feb 21, 2016)

Thanks for the links...  interesting stuff. Toward the end of the second link they showed various ways to support the blade holder which was interesting. Somebody made the comment that chatter is your lathe saying, "I'm not solid" which is undoubtedly a true statement. I tried locking the carraige and this had no effect...  probably a good idea in general but it didn't help the chatter at all. Now the other end of my brassed carbide cutoff tool is missing...  I finished the test cut with the AXA tool post (with a HSS blade set at an angle). Next step is probably a wider cutoff tool either HSS or maybe buy a blade with the changeable insert.


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## Ulma Doctor (Feb 21, 2016)

something else to check is the tension of the gibs to the dovetails in both the saddle and compound rest.
wear or maladjustment in these areas will make your parting suffer.

a trick to try is to invert the cutoff tool, run the lathe in reverse, and part from the back side of the work.
this may help if your lathe light or worn

P.S.
the suggestion of being above center greatly reduces the tools tendency to pull the work into the blade. 
the work has a hard time climbing over the blade and therefore has less of a chance of breakage.


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## Mork (Feb 21, 2016)

The dovetails are about as tight as I can get them without restricting movements. They are slightly tight in some areas which obviously means there is some wear and some movement. It's an issue I'm sure but something I need to work around. In my opinion, above center will help but if you are only very slightly above. More than slight and the undercut on the blade has to be ground significantly. I have tried various heights and always end up going back to center. It always works the best for me. I've considered going in from the back side but need to give this more thought. It would limit the diameter I can part but I'm not sure how much. Worth investigating and trying for sure. Ultimately I think my Logan 200 is a little flimsy. It's perfect for most things I do but for serious production work I'd want to get something much more solid. 

I think the next step is carbide inserts or perhaps cutting from the back.


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## mattthemuppet2 (Feb 21, 2016)

a picture of your set up would help. I have a much smaller and more flexible lathe, yet I can part steel without chatter. Chatter is either your tool set up flexing and springing back or your work flexing and springing back (or a combination of both). There are lots of things you can do to minimise both, but without seeing the set up that's causing the problems we may be directing you to fix something that isn't causing the problem.


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## Surprman (Feb 21, 2016)

Lock the carriage down (otherwise you will get movement that makes your part somewhat bowl-like.)  More importantly, drive the compound rest all the way forward on its screw prior to parting.  That was the trick for me (an actual machinist from work told me that).  Not only does it stiffen things up, but there is less of a chance the tool will grab the workpiece (especially brass) and pull the tip under the part (due to backlash slop).

Rick


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## Mork (Feb 21, 2016)

Here's my set up. I increased the relief below the cutting edge on the blade just to see if it made a change...  not much different. As you can see, I'm slightly above center here. I completed this cut adjusted slightly below center which seemed to help. The tool is T shaped and 3/32" wide. I read some comment that said wide is better so maybe I'll jump up to 1/8 or 5/32.  I had a brassed carbide insert blade used with a tool post I made but broke the carbide off both ends. This picture is at the beginning of this thread.


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## Mork (Feb 21, 2016)

Here's a short little video


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## mikey (Feb 21, 2016)

Mork said:


> I've considered going in from the back side but need to give this more thought. It would limit the diameter I can part but I'm not sure how much. Worth investigating and trying for sure. Ultimately I think my Logan 200 is a little flimsy. It's perfect for most things I do but for serious production work I'd want to get something much more solid.
> 
> I think the next step is carbide inserts or perhaps cutting from the back.



Parting from the rear is the same as parting from the front, except that it works much, much better. You can part anything that fits on your lathe, provided your parting tool is long enough. The key problem is going to be mounting such a tool because it requires T-slots on the cross slide. There was a post recently that pointed to a company that sells rough castings so guys with older lathes can put a T-slotted slide on their lathes. Parting from the rear works so well that if I had issues I would seriously consider modding my cross slide. 

I've used a rear mounted parting tool on my Sherline for well over a decade. True, some think its a toy and can't run with the big dogs but I've parted materials up to 1-1/2" over the cross slide at high speeds without a hitch, from brass to 4340. I typically run at speeds somewhere around 2-3 times normal turning speeds for the material without a catch, stutter or hint of chatter. I use only P-1-N tools on this lathe, which is 0.040" wide, and there is very little force required to feed the tool into the work. I don't even pay much attention to stick out because it isn't critical with a rear mounted tool. I don't lock my slides or adjust my gibs. (I went to this tool because this lathe chatters when parting from the front in harder materials. However, if I am careful with alignment I have parted 2" OD steel from the front with this lathe.)





This is a groove being cut in mild steel at 1200 rpm. Note the stick out of the blade - still couldn't get it to chatter. 

I also have an 11" lathe that parts from the front without any chatter so maybe this might help. I typically use a P-1 or P2 blade on it and very little feed force is required for it to cut cleanly at whatever turning speed I'm using. In contrast, parting with a GTN-3 blade does require more feed force but not a whole lot more if my turning speed is high enough. I like sharp tools but my parting tools seem to not be fussy about this; they get sharpened maybe once every few months (or more ).

Parting from the front does require me to do some things. The tool has to be absolutely *vertical* in the tool holder and then rigidly held. The tip has to be *on center*; I check it with a tool, not my eyeball. The blade has to be *perpendicular* to the work; I align the blade on the face of the chuck because its handy. I prefer a 7-8 degree relief angle at the front of the tool; this allows it to cut cleanly without rubbing or sacrificing edge support. When parting from the front I do pay some attention to stickout but only casually. I typically do not lock anything and feed manually so I can feel the tool cutting. Again, very little force is used once it starts to cut and I maintain a constant positive feel as I go in. Finally, I relax. If I get tense I cannot feel the tool cutting and that affects the cut. Stupid? Maybe ...

I will admit that my Emco 11" lathe is in good shape and not worn excessively. If it were old and loose then things might be different. I have had this lathe chatter a few times. Typically, the tool is not on center or perpendicular to the work. Once I fix that I can get on with it.

Hope this helps.


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## Mork (Feb 21, 2016)

Great post mike!  Hey... it sounds like parting from the back is the way to go... at least on my lathe. Take a look at the picture I just attached. I can do it without T slots although my diameter is limits to about 1-3/4" diameter. I don't like the limit but in most cases this is more than enough. I'll have to make a tool post but I set the one I made for the front side (complete with broken carbide tip) on the compound just to check clearances. Now I'm thinking about threading from the back also, for the same reasons, although I have had fairly good luck threading I do get occasional chatter on large threads. 

Thanks for the suggestions! 

Mark


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## Mork (Feb 21, 2016)

I just realized i could get a bit more (an easy 2 inch) by turning the compound around.


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## Mork (Feb 21, 2016)

Mike...  you are talking about normal rotation right...  with the tool mounted up side down?


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## mikey (Feb 21, 2016)

Dang, you're right - you can mount a rear tool post! Okay, my bad.

Yes, the lathe rotation is normal/towards you but the tool is mounted upside down. If you do this be very accurate when milling the slot for the tool as this sets your cutter height. The bottom of the slot must be on the dead center of the spindle. To do this I turned a piece of brass (any material will do) and took skim cuts until I got a very clean finish. Then I used a height gauge to check the distance from the cross slide where the tool mounts to the top of the work piece and subtracted half the diameter to get the spindle center height. Mic the OD of the work piece to be as accurate as you can.

I use the same principle to make a simple tool height gauge. It gets used a lot!

I'm not sure about threading from the rear - never tried it - but a rear mounted scissors knurling tool works better for me back there, too.

I know my last post seemed to go against what many of the other contributors said. I did not mean to imply they are wrong; only that my experience is different. If I offended anyone, I apologize and offer that it was not on purpose.


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## Mork (Feb 21, 2016)

I don't think you offended anyone. I know for a fact there are many that struggle with parting on a lathe. I even watched a video on youtube by Tubalcain where he said, "I've avoided making a video about parting on a lathe because it is something I struggle with".


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## T Bredehoft (Feb 21, 2016)

Ulma Doctor said:


> a trick to try is to invert the cutoff tool_, run the lathe in reverse_, and part from the back side of the work.



With the tool inverted and behind the work, the spindle should be turning naturally. Many lathes don't have the capability to mount a tool behind the work, but this sure is the best way to cut off work in a lathe.

I build an inverted tool to hold in my four tool holder in front of the work, but I have to be careful not to unscrew the chuck when parting off.


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## Mork (Feb 21, 2016)

Reversing with a inverted tool would be a great way to part off but I'd also be worried about my screw on chuck.


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## planeflyer21 (Feb 22, 2016)

Mork said:


> Reversing with a inverted tool would be a great way to part off but I'd also be worried about my screw on chuck.



If you are running the parting tool inverted on the back side of the chuck, directional rotation will be the same as right-side-up on the front.


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## Mork (Feb 22, 2016)

You're right planeflyer, I messed up....  got turned around. 

I tried the inverted tool (standard rotation of course) as Mikey suggested but I had some of the same problem. I then sharpened the parting tool an at a very slight angle and tried it again. It did work better and even better yet at higher speeds (except for it slinging oil and chips everywhere). Still some chatter however but I can see where some fine tuning might make it a better method. Be sure to stand to one side tho...  oil and chips sling everywhere. I'm thinking a thinner blade would be better... I think mine is 1/8"

Mikey said he used a .040 blade...  that is very thin but this would require much less force and stress on the lathe. I'll have to experiment.


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## mikey (Feb 23, 2016)

Something isn't right. There should not be oil and chips slung about when parting from the rear - the oil generally stops at the blade and the chips simply pile up on top. I guess it can happen but I've never seen it. 

If you're chattering I would check to see if you're on center height and perpendicular to the work. If I had to guess I would bet the tool is not centered.

Once you are, don't be afraid to crank up your speed. The tool will cut easier. You should feel a slight positive resistance to feed all the way through the cut. 

I think for a lathe of your size a P2 (about 3/32" wide) or a P2N (5/64" wide) would work well.


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## mattthemuppet2 (Feb 23, 2016)

I don't think anyone's asked this yet, but what material are you trying to part? I'd suggest getting a piece of delrin or plastic tubing and starting with that, then work up to aluminium and then steel. As Mikey says, something isn't quite right here, so start with the most forgiving material and work up from there. Could be that you're not feeding hard enough, so the tool rubs and chatters. You should be getting nice curls.


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## Big Bore Builder (Feb 23, 2016)

Overhang is your enemy.     Omit the overhang!!  Snug up the little jack screw.


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## Mork (Feb 23, 2016)

I went through my lathe and tightened everything up today. It wasn't in terrible need but there are a few area on my Logan lathe that in my opinion are very poorly designed. This area is where you adjust the carriage to the bed of the lathe. Both the front and back are basically snugging screws to remove excessive clearances. A much better method would be to install shims and tighten the saddle securely with .0001 slop. Its been a while since I have had the saddle apart so there may be a method of shimming and securing the operator side but on the back side there is no way to do this (not with the original design anyway). 

Mikey...  the back side of my saddle might be what is creating a problem. I used lock washers on the bolts holding the lip that catches the underside of the bed. This works fine while working from the front but the washers acted like springs when parting from the back side. 

Now that things are all tightened up parting from the front is better than it was...  even if my adjustments are all a little stiff now. I plan on trying a thinner parting tool with an insert next. I think parting from the back side is a great idea but its a bit awkward without T slots. I may explore this more in the future. 

I agree "Big Bore"...  solid solid solid. The thing is, the Logan 200 is not extremely solid. I may explore some modifications for tightening the saddle to the bed but there are limits as to how much I can solidify.


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## mikey (Feb 23, 2016)

Parting from the rear causes the forces on the blade to push the tool holder down. This usually takes up play in the supporting structures and improves rigidity. I checked this once with a tenths-reading indicator. When parting from the front I could see upward movement on the cross slide as the tool entered the work. From the rear ... nothing. Regardless of which way you go - front or rear - as long as you pay attention to the basics you should do okay.


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## atlas ten (Feb 24, 2016)

I am following this thread.  I have  hit and miss parting. For me hardest is larger diameter and harder steel. I like to have my parting blade ground to face the fallen part.
Jack

Sent from my SGH-I337M using Tapatalk


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## Mork (Feb 24, 2016)

Interesting...  I would think parting from the back would raise the back of the carriage although I can see how the force could transfer to the front. Maybe taking the play out of the carriage in front will help parting from the back. I'll probably try this again in the future.


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## Paul in OKC (Feb 24, 2016)

Parting is its own anomaly. Personally I don't like HSS blades as a whole. When a youngster in this trade I would pucker when parting off more than anything else. I have learned enough tricks to get by just about any  problem. Love the carbide replaceable inserts, but at home I still use a HSS cutter. Usual problem is in the rigidity of set up. I still pucker a bit. In fact when teaching at the Vo-Tech last year I was explaining the woes of parting off, then gave a demo. BANG! Snapped the HSS tool off. The guys jumped. "See, no matter how much experience you have __it still happens!"


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## dlane (Feb 24, 2016)

Mikey  I must be missing somthing , parting from the rear the work is rotating up , would that not lift the cut off tool and holding assembly's "verses " parting from the front the work is traveling down and the cutoff tool would have downward pressure ?. 
I haven't tryed parting from the rear , but that's just what's come to mind . Could the upward forces lift the assembly's into the dovetails resulting in increased stability and less chatter .?
Next time I part I'll get out the indicator , I'm useing a SB 10L and don't get much chatter.


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## mikey (Feb 24, 2016)

Mork said:


> Interesting...  I would think parting from the back would raise the back of the carriage although I can see how the force could transfer to the front. Maybe taking the play out of the carriage in front will help parting from the back. I'll probably try this again in the future.



If you think about it, the blade is being lifted when parting from the rear. That force has to go somewhere. It cantilevers that tool holder and pushes down on the carriage, taking up what play there may be. Once that play is taken out the forces are sustained by the entire cross slide and lathe bed and you can't get more solid than that. The best scenario is when the tool holder is bolted solidly to the cross slide, not sitting on top of the compound. 

When parting from the front the same thing happens except the forces on the blade push it down, lifting the tool holder up. This lifts the supporting structures and increases clearances. As the tool cuts the tool/blade/cross feed is going up and down so the chances of chatter are increased. 

In my feeble brain I think the reason so many guys tell you to force the tool into the cut is because of this lifting thing. Forcing the tool keeps the cutting forces high so there is less oscillation taking place. I don't know that this is true but conceptually it makes sense. It also makes sense to keep overhang to a minimum, tighten up your gibs, make sure you are dead on center height and perpendicular to the work to minimize cutting forces


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## John Hasler (Feb 24, 2016)

mikey said:


> If you think about it, the blade is being lifted when parting from the rear. That force has to go somewhere. It cantilevers that tool holder and pushes down on the carriage, taking up what play there may be. Once that play is taken out the forces are sustained by the entire cross slide and lathe bed and you can't get more solid than that. The best scenario is when the tool holder is bolted solidly to the cross slide, not sitting on top of the compound.
> 
> When parting from the front the same thing happens except the forces on the blade push it down, lifting the tool holder up. This lifts the supporting structures and increases clearances. As the tool cuts the tool/blade/cross feed is going up and down so the chances of chatter are increased.
> 
> In my feeble brain I think the reason so many guys tell you to force the tool into the cut is because of this lifting thing. Forcing the tool keeps the cutting forces high so there is less oscillation taking place. I don't know that this is true but conceptually it makes sense. It also makes sense to keep overhang to a minimum, tighten up your gibs, make sure you are dead on center height and perpendicular to the work to minimize cutting forces


Draw a free-body diagram.  You'll see that the net force exerted on the carriage by the work when cutting from the rear (doesn't matter what operation) has to be upward and to the rear.  When cutting from the front the net force has to be down and to the front.


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## mikey (Feb 24, 2016)

I've done that, John, and I've also tried to measure it, albeit with a dial indicator instead of strain gauges which I don't own. I've proven it sufficiently to myself so I won't argue the point.


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## mikey (Feb 24, 2016)

I should expand on my last comment, John. I wasn't trying to cut you off or anything. 

When parting from the rear the cutting forces push up on the blade's tip, which tends to lift the blade out of the cut. However, it is constrained from doing that by the tool post, which acts as a fulcrum. As these forces try to tip the tool post backwards, which they usually cannot do, they are transferred to the cross slide. Once any play in the cross slide is taken up the force then transfer to the bed. The reverse is true when parting from the front.


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## stupoty (Feb 24, 2016)

My lathe has a much beefier rear gib for up ward forces  than the front up face of the gib , my old 9x20 didn't have a top and bottom gib at the front at all it just sat on the ways so any harmonics that occurred would probably be bad.  I used to explode parting blades on my 9x20 a lot. :-0

Stuart


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## mancomp (Feb 27, 2016)

Try a piece of tire innertube or a rubber band on the chuck and a band rapped around the tool block, passive damping sometime works. dum dum putty in the corner of a tool block sometimes works also. These techniques are used on brake drum lathes to eliminate bell ring during turning and truing. Rick


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## Tozguy (Feb 27, 2016)

I don't see how parting from the back changes the dynamics of the cut compared to cutting from the front except that chips might be able to fall out of the way more easily. However there is no clear advantage to try outsmarting the design of the lathe by cutting upside downtown at the back, if you have a choice, unless there is something inadvertent going on.

Everything you have said mikey in favour of the forces when parting 'upside-down' apply more so to parting from the front.

To my mind the issue is to get the cut as close to the mounting point of the compound on the cross slide as possible. Further, upward pressure will put the fulcrum on the tool post centre bolt. Conventional downward pressure will put the fulcrum point on the outside edge of the tool post body which is closer to the cut.

If cutting upside down somehow puts the whole dovetail system to better use then would someone please walk me through the rationale.

What strikes me is that the weight of the carriage is biased towards the front so that the front way is carrying most if not all of the weight. There might even be some lift on the back way in some cases. What I want to avoid is a set up where cutting forces cause the carriage to teeter on the front way. On a 7+ inch wide bed like mine to get both ways to support the mass of the carriage more evenly, setting the tool post behind the cut might make sense. However I prefer to add a lead weight on the cross slide at the back to prevent teeter on the front way.


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## kbs (Feb 27, 2016)

Mork said:


> Here's a tool post I made for my Logan 200 lathe. The AXA post I have has the capacity for a 1/2" cutoff blade and I was hoping a 3/4" blade would be more rigid. The post works but really no better than the 1/2 blade on the AXA post. Does anyone have any suggestions for as to how to stop a tremendous amount of chatter? I've tried high speed and the slowest speeds. The slowest is by far the best but still not great. I also checked the bearing in my head stock...  as near as I can tell I have about .001 slop in the bearing which doesn't seem excessive to me.
> 
> I suspect I'm expecting a bit to much from a small lathe. The compound is nowhere near as solid and other lathes and the 1.5" head stock probably flexes under load. Still I'm hoping somebody has a good suggestion as to how to improve the chatter I'm getting.  Thanks.
> 
> ...


Hi, please google dale detrich's cut off tool holder, I made a couple, & they work great, no chatter, clean cuts, you'll be pleased. ken s.


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## TC0853 (Feb 27, 2016)

Mork said:


> Here's a tool post I made for my Logan 200 lathe. The AXA post I have has the capacity for a 1/2" cutoff blade and I was hoping a 3/4" blade would be more rigid. The post works but really no better than the 1/2 blade on the AXA post. Does anyone have any suggestions for as to how to stop a tremendous amount of chatter? I've tried high speed and the slowest speeds. The slowest is by far the best but still not great. I also checked the bearing in my head stock...  as near as I can tell I have about .001 slop in the bearing which doesn't seem excessive to me.
> 
> I suspect I'm expecting a bit to much from a small lathe. The compound is nowhere near as solid and other lathes and the 1.5" head stock probably flexes under load. Still I'm hoping somebody has a good suggestion as to how to improve the chatter I'm getting.  Thanks.
> 
> ...


What I've done with some degree of success comes in two parts. 1st, it seems that chatter is always a product of too much tool touching the workpiece. So I grind my tool so that it slopes towards the piece that will be coming off, and when it does seperate, it leaves a nice flat surface on the piece coming off, you can then face off the mound left on the piece in the Chuck if necessary. 2nd,  I slow the spindle speed down and keep the tool dug into the metal so I have a constant chip coming off of it, it never gets a chance to chatter like that. I don't know if it's necessary, but since the tool is ground to a point, I worry about getting it hot, so I back it out every several seconds to make sure it's not turning color, that allows me to get a little oil in that slot at the same time. And plenty of lubrication. Good luck.

PS: I've never had the nads to power feed it in, but 1 of these days........


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## larryr (Feb 27, 2016)

Mork said:


> Here's a tool post I made for my Logan 200 lathe. The AXA post I have has the capacity for a 1/2" cutoff blade and I was hoping a 3/4" blade would be more rigid. The post works but really no better than the 1/2 blade on the AXA post. Does anyone have any suggestions for as to how to stop a tremendous amount of chatter? I've tried high speed and the slowest speeds. The slowest is by far the best but still not great. I also checked the bearing in my head stock...  as near as I can tell I have about .001 slop in the bearing which doesn't seem excessive to me.
> 
> I suspect I'm expecting a bit to much from a small lathe. The compound is nowhere near as solid and other lathes and the 1.5" head stock probably flexes under load. Still I'm hoping somebody has a good suggestion as to how to improve the chatter I'm getting.  Thanks.
> 
> ...


i have two commercial cutoff tools for my bxa tool post. they both have back rake built into them. your holder dose not appear to have any rake, that may contribute to the problem. the tool must be on center to cut properly. on small lathes lock everything down. i would try high speed steel cutoff blades ,they require less pressure to cut and you can sharpen them yourself.. sometimes i find it necessary to use the tailstock for additional support. just back off prior to cutting through. this is a good way to test for loose spindle bearings. keep your tool stickout to the minimum amount needed to cutoff. when dealing with small lathes you kind of have to experiment with tooling and set ups to find a combination that works with your lathe.


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## rcwarship (Feb 27, 2016)

I've found that the backing gear on my Logan 200 eliminates all chatter & works very well.  Great thread all, thanks for sharing.


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## WyoGreen (Feb 27, 2016)

Parting is the one thing I still have problems with. I'll try out the suggestions in this thread to see if it helps any. 

Thanks to all the posters, Steve


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## Skillful (Feb 27, 2016)

Hi all. This is my first time here so please be gentle with me! I thought these few notes might turn out to be useful to someone. I am just a self taught beginner at machining since 1984. As with all of us I went through the mill (Ha ha pun intended) learning to part off confidently. With very small jobs I still use HSS in the tool post as its easy to grind to whatever shape/diameter is needed at the time.  I also built a back parting off tool with a carbide tip for big jobs and it will do the most amazing things. (See pic) I just can't make it fail. It will turn off 2 1/2"  mild steel at top speed (1500 rpm). I can force the tool in to the work so hard the swarf comes off glowing red hot. Mind you I only did that once to see if I could. Mostly I keep it to no colour or light blue.  I never have any chatter and of course with carbide I don't use lubricant.  (Sharp eyed observers will note that its time I had my tip sharpened.)
As we all know parting from the tool post is much more fraught so if I am using that method for small parts I use plenty of lubricant and slow speed, frequently withdraw the tool and brush out the slot with a old tooth brush using a separate brush to dribble oil on the cut.  One has to use ones brain, ears and fingertips to be sensitive to how the cut is going and how much feed is required. As someone else mentioned too light a cut and slow feed can cause chatter, too heavy cut and too fast feed can jam the tool and you need to be able to "feel"  each time it needs cleaning out. These days I _*usually*_ get away with it.

Not sure about all the theory of the back parting off tool but I have always suspected that because the tool is upside down  the chips/swarf clear the cut by gravity and that helps everything along.

Hope this helpful to someone, I will get off the soapbox now!  Cheers all   Joe


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## mikey (Feb 28, 2016)

Guys, at the end of the day, it doesn't really matter why a parting tool works from the rear or not. There are all kinds of theories and opinions and to my knowledge not a single one has been proven, including my own. In the past, the Brits have been the most vocal about the benefits of rear mounted tools, most notably GH Thomas, but as far as I know he never did any vector analyses. Even Myford, who sold a rear mounted tool post, did not prove anything. All they did was publish a picture of how they thought the forces went and commented that perhaps parting from the rear prevented dig ins as the cutting forces were encountered:




I do know that a rear mounted parting tool works rather well. Why it works is not as important as the fact that it works well. I do not mean to imply that it is the only way or that it is better than parting from the front - it clearly is not for many of us - but it is a viable option and it beats the heck out of using a hacksaw.


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## Tozguy (Feb 28, 2016)

Count me in with the folks who want to know why a certain method or tool works better or worse than another. Before I make a special rear parting holder and blade it would be important to understand the critical design features that will make it better than what I already have.
The 'whys' that I have learned so far about using a lathe properly have been fascinating and satisfying.


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## Tozguy (Feb 28, 2016)

Joe,  welcome aboard and thanks for the picture. That is an interesting design. If it puts the cutting blade in tension instead of the usual bending mode I am sold. However I am not able to visualize how it cuts and how to feed it. Any details that you could provide would be appreciated.


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## GK1918 (Feb 28, 2016)

food for thought cause I didn't see this mentioned.   Front or back I don't think it matters but
most parting is done from front for a tool change.  For the most part most buy HF or China
blades (me too) because we do a lot of brass parts and they work fine, but have you looked
at the end of the blade while holding the tool  holder in your hand.?  You will find the blade
is crooked.   Therefore I use two blades, one upside down, now the cutting edge is vertical.
Get the picture.  End view thick at the top narrow at the bottom equals a cocked blade........


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## Tozguy (Feb 28, 2016)

GK could we see a picture of your holder? Just want to check if I understand it properly.


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## Wreck™Wreck (Feb 28, 2016)

Having never used a hobbyist type lathe I have no experience here.

That being said, I can not see any advantage to parting from the back unless one has run out of room for another tool on the cross slide or cycle time is a priority.

I suppose that lifting the cross slide off of the ways may impart a bit of  chatter relief, this again I do not know, interesting concept however.


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## John Hasler (Feb 28, 2016)

Wreck™Wreck said:


> Having never used a hobbyist type lathe I have no experience here.
> 
> That being said, I can not see any advantage to parting from the back unless one has run out of room for another tool on the cross slide or cycle time is a priority.
> 
> I suppose that lifting the cross slide off of the ways may impart a bit of  chatter relief, this again I do not know, interesting concept however.


Parting from the front the toolpost bends forward, causing the tool to dive into the cut.  Cutting from the back the toolpost tends to rock back, pulling the tool out of the cut.  Might not be better, but at least it's a different set of problems.


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## Wreck™Wreck (Feb 28, 2016)

Thank you.

I sometimes run LH tools from the back when I do not have the correct tool for the job, if making 50 or more parts the chance of running the spindle the wrong direction is almost assured at some point, carbide insert tooling does not like this (-:


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## Profkanz (Feb 28, 2016)

Wreck™Wreck said:


> Upon reading the Kyocera  parting tool literature that I posted above a few things pique my interest. I have never read the booklets that come with the tools that I use because I am lazy and they are not my tools.
> 
> They advise setting the tool above the center line , I suspect that this is to account for a certain amount of tool movement even if you are running the coolest  Swiss lathe.



Setting the cutoff tool slightly (.005-.010) above center and ensuring that there is plenty of end relief makes for better chipflow and less end back pressure in the cut.


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## mikey (Feb 29, 2016)

Tozguy said:


> Count me in with the folks who want to know why a certain method or tool works better or worse than another. Before I make a special rear parting holder and blade it would be important to understand the critical design features that will make it better than what I already have.
> The 'whys' that I have learned so far about using a lathe properly have been fascinating and satisfying.



Toz, I can't tell you that parting from the rear is better for you; just better for me and apparently many others. As to why it works, there are many theories as mentioned but nobody has proven anything to date as far as I know. My opinion on the advantages are:

The cutting forces lift the tip out of the cut if the cut falters; dig ins are rare, as is chatter. 

It improves the apparent rigidity of the lathe when parting, however it does it.
Cutting fluids get to the tip more readily instead being lost with the chips, thereby reducing friction and cutting temperatures.
Most rear mounted tools are bolted to the cross slide itself instead of being perched on top of a tool post. This greatly improves rigidity whether parting from the front or rear.
It works good! It allow me to part at very high speeds, which makes parting smooth and easy because I don't worry about chatter or dig ins. Because of the design of my tool I can go from pulling the tool out of the drawer to cutting in under 10 seconds - I do this all the time. I haven't chattered or dug in in over a decade. Is it any wonder that I think this is a viable option?
I usually try to stay away from discussions on parting other than to offer things that may help. The reason is that the discussion about rear mounted tools always evolves into a "how does it work?" kind of thing or "what proof do you have?" I know how I think it works and have proven it to my personal satisfaction. I don't expect anyone else to buy it; I can only hope folks can keep an open mind about it.


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## Tozguy (Feb 29, 2016)

mikey said:


> Toz, I can't tell you that parting from the rear is better for you; just better for me and apparently many others. As to why it works, there are many theories as mentioned but nobody has proven anything to date as far as I know. My opinion on the advantages are:
> 
> The cutting forces lift the tip out of the cut if the cut falters; dig ins are rare, as is chatter.
> 
> ...



Mikey, thanks for sharing your thoughts with us. Please know that I am not asking for proof of what you say. I believe every word you wrote and don't question the validity of your statements. My questions only relate to my relative ignorance and my need to understand the 'why' of it. My approach to this hobby is not to just get the job done but to learn as much as possible about a lathe. Sorry if I sound skeptical sometimes because its not the case.


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## atlas ten (Feb 29, 2016)

I like to think simple when using lathe. Kinda like the quote "each action has an equal and opposite reaction". 
Jack

Sent from my SGH-I337M using Tapatalk


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## mikey (Feb 29, 2016)

Tozguy said:


> Mikey, thanks for sharing your thoughts with us. Please know that I am not asking for proof of what you say. I believe every word you wrote and don't question the validity of your statements. My questions only relate to my relative ignorance and my need to understand the 'why' of it. My approach to this hobby is not to just get the job done but to learn as much as possible about a lathe. Sorry if I sound skeptical sometimes because its not the case.



Okay, I just didn't want to leave the subject hanging. Unfortunately, this is one of those "why's" for which there are a lot of "I think's" but not a lot of "I know's". I will say that back in the old chatter days I was ready and willing to try anything, whether or not it made sense to me at the time. This was one of those times when I'm glad I did.


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## Tozguy (Feb 29, 2016)

So far the discussion has helped me to see the limitations of my current parting tools and motivate me to try something with a better concept. So I thank you all.


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## Woodemp (Mar 2, 2016)

Hi Mark.  I've used this type of cut-off tool with good success. But, on large rigid lathe's.  I learned the tool needs to be grounded first. I would increase the front clearance to between 10 to 15 deg.
Grind the front cutting edge back about the same amount from left to right.
Grind a chip breaker with extreme back rake.
Hand feed. Feel the machine. Use the rate of feed determined by the chip. If you don't give it enough feed it will rub and wear the tool and then hook. 

Also, depending on the size of the workpeice, I would set it slightly below center. A 4" diameter I would set it about 010" below center.

Good Luck


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## Wreck™Wreck (Mar 5, 2016)

Not a parting operation but similar, plunge cut a V-Groove, 104° included X .308" depth, I would not have plunged it but didn't have a suitable tool otherwise.
Ground a brazed 90° bit on a surface grinder, the parts are 3.307" OD 304SS and they ran very quietly without chatter with an excellent finish until the 7th of 10 when I had to sharpen the tool. 45RPM's, .001 IPR feed rate with a 2 second dwell .025" from the bottom. I did use a live center.

The second groove has the same angles but a wide flat bottom, ground another brazed tool and profiled this feature, the chips were a NIGHTMARE with this tool. 530 RPM's, .025" DOC, .008 IPR feed rate roughing, .008" DOC, .004" IPR feed for finishing. The bore has several diameters and 1 internal groove.

Done with a Bridgeport 15 X 48 CNC chucker lathe.

All in all some very tedious parts.


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## fgduncan (Mar 12, 2016)

I have found that working as close to the chuck helps things out a lot. Also, even if you don't think you need to use one, a steady rest or follower rest may provide the extra support you need.


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