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Cut off tool use

Tecmec

Plastic
Joined
Aug 29, 2009
Location
Connecticut USA
I have a vintage South Bend 9. I have noticed that when ever I try to use a cut off tool the tool will start a cut and than seem to ride on the surface (I.E. not create a chip) then it will bite in to the material big time creating a large chip or causing the the tool and material to bind bogging down the lathe or digging into the material to the point of dislodging it in the chuck. Material I am working with is mild steel. I have been manually feeding the tool at a very slow rate. The cut off tool is mounted in a Phase II holder. Could I be seeing the effects of too much cross feed wear/backlash or loose gibs on the cross feed? (I do have a fair amount of backlash in the cross feed) Any advice or comment is appreciated. Thanks
 
Your biggest problem is the lathe. These machines are very light and not very stiff. They are very useful machines, but they are incapable of performing heavy cuts. Generally, you should refrain from using cutoff tools in this machine. You will note that the whole compound will visibly flex under tool load. Of course, any looseness in the machine does not help and will only aggravate the problem, but the problem is the machine itself. I have a 10k which is essentially the same machine and it is in like new condition and it suffers the same problems. I use my other lathes for cutoff operations. The Phase II cutoff holder and tool will work perfectly on a stouter machine. In point of fact, these tool jams are dangerous in your machine to both yourself and the machine. I have witnessed fractured compounds and tool explosions on both the SB9 and 10k.
 
where to start?

Ph2 holders *suck* - if you look at one carefully you will see that the pocket the blade sits in is straight...so presuming you are using a decent blade, the blade will either have tapered sides or be a T type blade...either way it's not gonna sit in that holder right giving the necessary side clearance without some fiddling...If you are sing a T type blade you can simply file a groove in the holder for the "T" and then the blade will sit right.

Ok, so you get that worked out and it still sucks...assuming your tool is correctly sharpened(it should start cutting "on contact")....do something counter intuitive...turn up the speed and be aggressive with the feed.

Pic of issue with ph2 holder in this thread-

http://www.practicalmachinist.com/v...ase-ii-cut-off-tool-243090/?highlight=Parting
 
Using a cut-off or "parting" tool one one of these lathes is a bit of an art. First, you must have a sharp tool with the correct relief angle at the point. Second, you need to do the cutting operation as close to the headstock as possible AND if possible, support the outer end of the workpiece with a tailstock center--either live or dead. Third, the tool point must be exactly at the center height.

Use plenty of a good quality cutting fluid as you make the cut and make sure the parting tool is exactly perpendicular to the work piece. Sometimes, if the diameter to be cut is large, you may find it helpful to widen the cut slightly by making a second cut which is maybe half the width of the tool. This will give you some additional side clearance.

If you're using a quick change tool post, you may find that one of the parting tools with a carbide insert does a pretty good job. The downside of those tools is that they are expensive, the make quite a wide cut, and they are extremely fragile.

And last, once you get a chip going continue to feed the tool in while applying lots of cutting fluid.

As I said, it's a bit of an art and with practice you'll develop a "feel" for the correct feed rate. Don't give up. Practice more.
 
I had similar issues when parting on my SB 10L, the parting blade seemed to jump and ride over the work. Broke many blades and damaged a lot of work. The problem was the headstock bearings were not properly adjusted..... Once I addressed that issue, my parting troubles disappeared.
 
where to start?

Ph2 holders *suck* - if you look at one carefully you will see that the pocket the blade sits in is straight...so presuming you are using a decent blade, the blade will either have tapered sides or be a T type blade...either way it's not gonna sit in that holder right giving the necessary side clearance without some fiddling...If you are sing a T type blade you can simply file a groove in the holder for the "T" and then the blade will sit right.

Ok, so you get that worked out and it still sucks...assuming your tool is correctly sharpened(it should start cutting "on contact")....do something counter intuitive...turn up the speed and be aggressive with the feed.

Pic of issue with ph2 holder in this thread-

http://www.practicalmachinist.com/v...ase-ii-cut-off-tool-243090/?highlight=Parting

I disagree with your PhaseII assessment, if you use the correct blade. My Phase II requires a "T" shaped blade it sits solid and works very well on my late model 13 x 40 SB. It will not work worth a damn on my 10K. The tool requires more machine stiffness and power than the 10K has. I totally agree that using a cutoff blade can be a bit of an art. Practice and attention to detail is very important, but the OP is pissing into a typhoon with his SB 9.
 
I have a 10K as well. I've never gone as big as iwananew10K, but I've been successful using HSS .1 wide cutoff tools in a phase II AXA clone and toolholder. My technique:

1. Make sure the tool geometry is correct and sharp. I use a diamond hand lap after sharpening.
2. Use the minimum stickout possible.
3. Make sure the cutoff tool is absolutely square to the work and centered vertically on the work.
4. Run the lathe on the lowest non-back gear speed.
5. Lock the carriage in place.
6. Tighten the compound gib to lock it.
7. Use plenty of lubricant.
8. Feed firmly. If you can't do the three hand dance of turning the crossfeed steadily and lubricating at the same time, feed in steps.
9. If chips are building up in the cut, pull back immediately and clear the chips.
 
I do cut off operations all the time on my 10K with no problems, so I see no reason why you should not be able to with your 9. It sounds like your cutoff blade may not be ground with enough relief or that it is not square to the work and on center. Lots of good suggestions in this thread, so don't give up - there's a learning curve to most everything.
 
You might try a spring-type cutoff tool holder. These have a built-in flex that lets the tool spring away from potential gouges. Mr. Pete uses one in his latest YouTube video series making a spindle nose protector. They squeal from the vibration but seem to work better on lightweight machines. They also seem to work well for form tools that have a lot of tool edge engagement with the workpiece. Good luck!
 
I use a cutoff tool on my South bend 9" tons of time. I use a 3/32" parting tool on my phase tool holder, for a 1" diameter I turn it about 250rpm or so and feed it good. You do not turn smaller parts with a cutoff tool at a low rpm. For a 1/2" part I use top gear. The biggest part I have cut off would be about 3-1/2" in diameter. An 1/8" wide blade is a little wide for the 9" and 10k lathes.
 
Using a cut-off or "parting" tool one one of these lathes is a bit of an art. First, you must have a sharp tool with the correct relief angle at the point. Second, you need to do the cutting operation as close to the headstock as possible AND if possible, support the outer end of the workpiece with a tailstock center--either live or dead. Third, the tool point must be exactly at the center height.

Use plenty of a good quality cutting fluid as you make the cut and make sure the parting tool is exactly perpendicular to the work piece. Sometimes, if the diameter to be cut is large, you may find it helpful to widen the cut slightly by making a second cut which is maybe half the width of the tool. This will give you some additional side clearance.

If you're using a quick change tool post, you may find that one of the parting tools with a carbide insert does a pretty good job. The downside of those tools is that they are expensive, the make quite a wide cut, and they are extremely fragile.

And last, once you get a chip going continue to feed the tool in while applying lots of cutting fluid.

As I said, it's a bit of an art and with practice you'll develop a "feel" for the correct feed rate. Don't give up. Practice more.

I do not agree with the "support the other end" part. You can use tailstock support up to a point, but retract well before you go through.
 
*Tubalcain* should be smacked for promoting spring holders.:)

I say this because I bought one based on his site...It was a POS.

like Mike said...once you get a feel for it crank it up and let the chips fly.

3/4" 1018 @ ~800rpm and .005/rev power feed, modified ph2 holder with 3/32" blade- this was on my Sheldon but my 9" would do the same.

134591838.mp4 Video by iwananew1k | Photobucket

I loved parting.:)
 
Everything is very well covered above. My small Logan is probably a flexible flyer compared to the Southbend, but I have little trouble parting off. The big thing is not to use a 1/8" wide blade, as it will chatter no matter what. Go with the narrower 3/32. T-blades will work in the holder if you cut a strip of brass shim stock and put it near the bottom to keep the blade vertical. I've thought about putting a couple set screws in the holder for that, but haven't tried it yet. The tip of the blade should be square, otherwise the blade will want to pull left or right.
 
I have always had good luck with parting tools but when you think about of perhaps 1/16, 1/8 or 1/4".. when was the last time you took a 1/16 or a 1/8 depth of cut. That is a lot of DOC for a small lathe and so down push pressure is much. Think one should measure blade top width and the bottom width then see half that when bumped to a chuck face, zero difference on the blade then it should lay dead flat.

But first before even mounting the blade, take a ball peen hammer and set the handle-but on the tool holder and with indicator set to near the top give a good two hands push down.. The tool holder should be solid… any tilt or saddle way sponnigyness is a killer to a parting tool. One might have to better center the tool holder, put the blade on the other side or shorten something to make it rock soled.
 
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Not been a fan of the cutoff blade holders used on my 9A, primarily due to the design that places the blade at an angle to the work rather than horizontal. Sharpen the tool? That changes the length and therefore the height...requiring adjustment of the toolholder height every time.

I don't get the reason for that...

I use AR Warner HSS holders and inserts. I don't do much parting- but do a lot of threading and just purchased this for my relief grooves instead of using a parting blade in the PII :

Arthur R. Warner Co. | Specialists in High Speed Steel - Kit #23 1/2 inch Cutoff Groover Right Hand

If I find regular need for parting larger materials they make a dedicated parting tool- which incidentally holds the blade horizontal.

Arthur R. Warner Co. | Specialists in High Speed Steel - Kit #28 3/8 inch Parting Tool

Carbide is just not compatible with the small dia hard steel and thus low speeds I typically work with.
 
I like the angle as a small positive rake is usually a good thing on a small low power machine. That does remind me, yo have to grind more clearance since the blade is tilted up a bit. It's a carbide world and people tend to be conservative on clearance, to keep the edge well supported, but with HSS I find generous clearance helps. If you have to force the tool into the work, something's wrong.
 
I have a 10K as well. I've never gone as big as iwananew10K, but I've been successful using HSS .1 wide cutoff tools in a phase II AXA clone and toolholder. My technique:

1. Make sure the tool geometry is correct and sharp. I use a diamond hand lap after sharpening.
2. Use the minimum stickout possible.
3. Make sure the cutoff tool is absolutely square to the work and centered vertically on the work.
4. Run the lathe on the lowest non-back gear speed.
5. Lock the carriage in place.
6. Tighten the compound gib to lock it.
7. Use plenty of lubricant.
8. Feed firmly. If you can't do the three hand dance of turning the crossfeed steadily and lubricating at the same time, feed in steps.
9. If chips are building up in the cut, pull back immediately and clear the chips.

What he said.

Most folks feed a cutoff tool too slow. Try cutting off one inch brass bar, feeding manually. See how fast you can
run the tool in. In principle that's the feed rate you can use for 1018 but of course it doesn't quite work that way.

Another intesting test is to profile a 3/8 square HSS tool to be a mini-cutoff tool, narrow down the end to be about
3/32 wide and put the correct front and side relief on it. Leave the top dead flat. Make the blade portion only
about 1/4 inch long, and try using that (basically a grooving tool) as though it were a cutoff too. You can feed a
good deal faster with that because the shank and the tool holder is more rigid.

For gummy stuff like 1018 consider the black sulfurized cutting oil.

As for speed, keep increasing the speed until you get chatter. The cutoff tool ideally should be run at the correct
SFPM as any too - what limits this is chatter or another work for 'setup not rigid enough.' If the spindle speed
is too low the part gets snapped off at the very end of the cut, the blade just pushes it off the stock.

Anyone who's ever run a headstock mounted cutoff tool like hardinge makes, understands how important the
rigidity of the setup is. Those things don't even have a leadscrew - they're lever acting. Go as fast as you want.
 
I had reasonable success with high speed steel cut off blades in my 10K using a a Phase II-like tool post, but recently made a rear mount tool post from the MLA casting, and switched to a carbide insert tool. I like it much better. The tool produces spiral chips that fall down out of the cut (tool is upside down on the rear mount post). I haven't used it on steel yet, but I cut off a 1 inch thick aluminum ring after trepanning from a 6 inch aluminum round, and had no trouble with a 3 1/2 cast iron round with a 3/4 bore. Power feed at 0.004 has worked well. I mounted the tool about 0.005 below center (remember it's inverted). This is a cheap carbide insert tool from Shars. I've seen several complaints about these, but they've word fine for me. Ran at 100-150 rpm in back gear on these larger diameters.

Jon
 








 
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