# Cut-off tool



## las3r (Apr 29, 2012)

Hey guys I'm looking for a good cut-off tool for my mini grizzly lathe any idea what to buy ? And I have a QCTP mounted on it

I have a HSS cut off but it does not go low enough to cut any thing and sucks


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## precisionworks (Apr 29, 2012)

http://www.ebay.com/itm/TMX-GTN-2-D...8?pt=BI_Tool_Work_Holding&hash=item45f35c26c4

That's pretty much the perfect holder for any lathe under 18" swing. FWIW my machine uses the identical tool holder. GTN2 inserts are inexpensive & plentiful on Ebay. You'll need to buy the block that holds the blade.


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## gadget_lover (Apr 29, 2012)

The nice thing about the standard hss parting blade is that you can use your grinder to take a small amount off the top, leaving the top rake that makes for easier cutting on a small lathe. This lowers the cutting height. It takes only a minute to do.

Here's a picture of how I ground mine, and it works great. 







Daniel


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## las3r (Apr 29, 2012)

I never thought of grinding it.... I might try it since I have the toolpost holder for it all ready


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## gadget_lover (Apr 29, 2012)

Yeah, since you have it, you might as well give it a try.

The trick (as it has worked for me is)
1) make sure it's at a 90 degree angle to the work so it goes in straight. I use a machinist square but many ways will work.
2) Tighten the cross-slide gibs so that there is no play at all. You will be using the cross-slide to move the tool, so you can even tighten it enough to lock the gibs.
3) Run the spindle speed at about 1/2 the speed you'd turn it.
4) lock the carriage in place so it does not move (the 9x20 has a carriage lock) 
5) make sure the cutting edge is sharp. I use a grinder, then a small diamond hone to make it sharp.
6) make sure there is some top rake. It does not have to be a lot. ( see my picture) 
7) make sure the cutting edge is on center, possibly up to .005 below center. Above center will cause it to dig in.
8) dribble cutting fluid as you part it.
9) back it out and clear the chips if it sounds like it's chattering.

That works for me every time. Parting is not as exciting for me as it is for some folks. 

Daniel


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## las3r (Apr 29, 2012)

Awesome thanks for the tips


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## KC2IXE (Apr 29, 2012)

Probably the best description of the "art" of parting off in the lathe was posted many years ago by the late "Teenut" - Robert Bastow. Miss the guy still

http://yarchive.net/metal/parting_off.html


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## precisionworks (Apr 29, 2012)

IMO the best parting tool is (and always has been) the band saw.


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## will (Apr 30, 2012)

precisionworks said:


> IMO the best parting tool is (and always has been) the band saw.



+1


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## gadget_lover (Apr 30, 2012)

precisionworks said:


> IMO the best parting tool is (and always has been) the band saw.



-1 

IN MY OPINION.... 

I find the bandsaw is good for many things, but it is no replacement for a parting tool. I always have to clean up after the bandsaw. I have to cut long and then face it because it's never quite straight enough. The bandsaw is accurate to 1/16 inch. The parting tool to within .001 inch.

A cold saw might be a good substitute in many ways. I don't have room for one.

Daniel


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## will (May 1, 2012)

I have a mini lathe 7x10 and I use a parting tool that is .040 wide. I do use it as I do not have a band saw. I still have to face off the back because the finish is never as good as a face cut. Like many things in life, depends on what you are cutting, how many you are doing, is it quicker to remove the work and move it to the band saw, etc. etc....


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## precisionworks (May 1, 2012)

Back when I bought my first lathe (actually well before the internet) an old timer told me to buy a band saw for parting off. The band saw is my most used part off tool although the cold saw does a much nicer job, leaving a milled finish & holding +/- .004 (.1mm) when using the stop. 

Lathe parting is done on small diameter parts, mostly 1.5"(38mm) or less. Strange as it sounds there's only one material that parts really well on my machine ... Ti-6-4. Everything else falls into acceptable, bad, worse, etc. Parting is a form tool operation for all practical purposes. The tool is forming a square groove. Almost every form tool wants to chatter & many parting cuts follow suit. The lathe is designed for shearing cuts & parting is not.


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## unterhausen (May 2, 2012)

I think even my crummy lathe is better at parting than a bandsaw. I guess it depends on what you are doing, If you are going to want fully finished/perfectly dimensioned parts, you are going to have to put the part back in the lathe and might as well bandsaw. For a lot of the work I do, the parting tool leaves a good enough surface to call the work done. That would not be the case on a bandsaw.


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## wquiles (May 2, 2012)

I don't think of parting on the lathe or the band saw as exclusive. I actually see both parting methods as being complementary.

- For parting of a piece of a longer rod, to then chuck on the lathe for some operations/process, about 99.9% of the time it goes in the band saw.
- For parting of a finished piece, 99.9% of the time I part on the lathe for smaller parts. For anything larger or "iffy" (like a solid rod of over 1" dia), I then grove on the lathe, cut on the band saw, and then finish (face off) on the lathe.

For example. I am about to make these Bearing Bronze retaining rings for the Sunwayman V10R/V11R LED light. I cut the 7-8 inch piece I need in the band saw, and then start working on the lathe with it:






But after making the parts, the finished pieces are cut on the lathe:











But parting on the lathe requires the right setup and cutting tool. Not to start a religious war on inserts vs. HSS, but in "my opinion", anyone starting today as a machinist should skip the HSS and grinding, and head straight to inserts. Specifically, the parting tools using inserts are superior to HSS not only on being ready to use ("never" having to adjust the blade "is" a huge factor for me), but also far more durable, come with various built-in chip breakers, correct coatings for various metals, etc.. Except for cost, inserts are the way to go, hands down.

I particularly like the Do-Grip from Iscar for the thicker blades and deep cuts (1.5" to 2" dia), but those inserts (although strong) are .118" wide. I also sometimes use a solid carbide tip (M100 micro carbide) which is very, very sharp, but it is 0.125" wide at the cutting tip for cutting Delrin rod up to about 2" in diameter. Although my setup is very rigid for these "wide" blades, and I don't have problems with an insert that wide on my 12x lathe, it does waste a lot of material, specially when making several back to back parts that are thin (some 0.025" thin). So, I am now using a much thinner blade/insert from Iscar whose inserts are only 0.063" wide, and SHARP!


Here are both the solid carbide cut-off blade on the left (0.125" wide) and the 0.063" wide Iscar:











And the narrow cut-off blade in action:






Will


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## darkzero (May 2, 2012)

I use the bandsaw as much as I can but I part off in the lathe much more. The bandsaw is too slow (except for alum & brass). But I don't work with diameters larger than 2" very much at all. Most of my work is smaller items, usually turned to final diameters & lengths & finished before parting off. Not always can I use the bandsaw to cut the finished pieces off & I would have to be more careful not to screw up the finish. I rather part off & catch in my hand. Even with the larger diamters, I use the parting tool, as much as I can, then cut with the bandsaw. It's just much quicker to do that way.


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## precisionworks (May 2, 2012)

> anyone starting today as a machinist should skip the HSS and grinding, and head straight to inserts.


+1

I had to show my instructor that I could grind a tool with all the correct angles, rakes, etc. in 1967 IIRC. We would still grind a few specialty tools during the 1970's but by then the price of inserts had dropped dramatically & all the big shops ran them - as did most small ones. 

If you like history you'll want to know that the first large metal cutting machine tools were water-powered cannon boring mills. These were built in Italy in the early 1500's. Heavy lathes for machining rolling mill rolls were used in Swedish iron mills in the early 1700's. By the 1850's the early English machine tool builders had perfected many designs. Frederick W. Taylor, working with Maunsel White at the Midvale Iron Works (Philadelphia PA) developed HSS about 1905. Taylor summarized his development work in the landmark research paper _On the Art of Cutting Metals _which was delivered to a convention of the American Society of Mechanical Engineers in 1906. HSS tools were phenomenal because they allowed machining at 100 sfpm (30 m/min), over twice as fast as carbon steel. 

In the 1930's the Krupps company introduced sintered tungsten carbide tools, first in brazed form & later as a detachable insert. Carbide tooling was significant because it allowed running the tool twice as fast as HSS, about 200 sfpm (60 m/min). The development of coatings for carbides raised the bar again, with speeds up to 400 sfpm (120 m/min). 

The time spent learning to properly grind HSS tools can be better utilized in learning correct operation of the lathe & mill, including proper job set up on that equipment. High quality machine work is the goal for many or most of the readers on this forum. Inserts will shorten the learning curve.


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## LukeA (May 2, 2012)

precisionworks said:


> If you like history you'll want to know that the first large metal cutting machine tools were water-powered cannon boring mills. These were built in Italy in the early 1500's. Heavy lathes for machining rolling mill rolls were used in Swedish iron mills in the early 1700's. By the 1850's the early English machine tool builders had perfected many designs. Frederick W. Taylor, working with Maunsel White at the Midvale Iron Works (Philadelphia PA) developed HSS about 1905. Taylor summarized his development work in the landmark research paper _On the Art of Cutting Metals _which was delivered to a convention of the American Society of Mechanical Engineers in 1906. HSS tools were phenomenal because they allowed machining at 100 sfpm (30 m/min), over twice as fast as carbon steel.
> 
> In the 1930's the Krupps company introduced sintered tungsten carbide tools, first in brazed form & later as a detachable insert. Carbide tooling was significant because it allowed running the tool twice as fast as HSS, about 200 sfpm (60 m/min). The development of coatings for carbides raised the bar again, with speeds up to 400 sfpm (120 m/min).



All in the pursuit of better hot hardness while maintaining acceptable thermal and mechanical shock resilience. With PCD inserts and specially designed and engineered processes, cutting speeds of thousands of sfm are attainable.


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## koala (May 3, 2012)

wquiles said:


> Not to start a religious war on inserts vs. HSS, but in "my opinion", anyone starting today as a machinist should skip the HSS and grinding, and head straight to inserts. Specifically, the parting tools using inserts are superior to HSS not only on being ready to use ("never" having to adjust the blade "is" a huge factor for me), but also far more durable, come with various built-in chip breakers, correct coatings for various metals, etc.. Except for cost, inserts are the way to go, hands down.
> 
> Will



Agree 100%, coming from a 6 months beginner who spent countless hours and money on silly HSS tool blanks and grinder. Today the inserts are far more superior with special coating for specific purposes. You will never believe the mirror finish you get from these coated inserts vs HSS. Those people who encourage HSS on the internet hasn't been updating their finding or maybe they live not trying new inserts.

I've been wanted to say this for months but I wasn't confident enough as I am relatively new to machining, but as more and more turned, I am pretty sure of coated inserts. I use HSS for roughing turns then finish with coated inserts. I try to keep mess to minimum so I cut dry at all times except for center drill and boring. Still on my first edge of the coated insert, no wear detected upon inspection with magnifying glass after ~200 hours of turning. These TCGT inserts are so sharp, that it doesn't matter what feed rate I use as long as it doesn't jam it.


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## KC2IXE (May 3, 2012)

There are times where HSS is VERY useful (oddball form tools where you don't have CNC), that said, I donated most of my HSS to my daughter's school, where they still use them (I have to get them a QCTP, and then they can use the carbide holders I gave them)

Now here is the fun RE Machining the Tee nut for the QCTP - I can do it here, quickly, and easily. I can do it there on thier RF-45 Mill. I can use the job to train some of the kids, or...

I can play, and use a shaper for the first time, just to say I've done it - I gather it hasn't been turned on in YEARS, but it might be fun to do it


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## precisionworks (May 4, 2012)

KC2IXE said:


> I can play, and use a shaper for the first time, just to say I've done it - I gather it hasn't been turned on in YEARS, but it might be fun to do it



Watch where you put your fingers & verify the ram stroke before using any shaper. They have a well deserved rep for amputations & for punching holes into heads 

I learned to run a good sized shaper from an old timer who was a great instructor. He'd set up the job, stand off to the side, hit the power switch & verify that all was good. The machine was a 24" Cincinnati that weighed about 6000# (2700 kg). The vise alone was a good 300# (135 kg) & we always used the overhead crane to move the vise. Shapers sales declined when Bridgeport brought out their "new" knee mill in 1938. Few shops had a shaper in the 50's, fewer yet in the 60's, almost none by 1970. 

Running a shaper always reminds me of running a table saw without a guard & without a rip fence :shakehead


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## Th232 (May 4, 2012)

Funny you mentioned shapers. I admit I had to look up what it was, but when I saw it I was reminded of this video:

http://www.youtube.com/watch?v=zrFR_lwZBRA&feature=player_embedded


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## Lyndon (May 8, 2012)

Only time I've ever seen a shaper is driving past a machine shop near my son's school. They have a rusty one out front with a mailbox bolted to it


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