# Positive Stop Insert Cut Off Blades



## maker of things (Oct 29, 2015)

Do you think my 1440 E LB could make good use of this type of parting/cutoff blade?  i.e. is the machine rigid enough etc.  





I work mostly with steel.  I like the idea of the insert being wider than the blade for deep cutting.  Assuming thicker blade = more rigid doing deep cutting; what do you think would be the widest insert that my lathe could use effectively?


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## tmarks11 (Oct 29, 2015)

No problem.  Those cut great.  I don't have that style of holder, but use a similar insert.  My insert is 0.094" thick.

You will like it much better than using HSS cut-off blades.

I use one of these, because I like the positive clamping action of the cap screw, and the shape makes it much stiffer and less prone to chatter. Downside is that you can't part anything more than 1.25" in diameter with one of these.

http://www.iscar.com/eCatalog/item.aspx?cat=2301399&fnum=557&mapp=TG&app=52&GFSTYP=m


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## mikey (Oct 29, 2015)

I use the Aloris version of that blade on my 11" Emco Super 11CD so I should think a 14" lathe is more than rigid enough. Aloris uses a GTN-3 insert (1/8" wide) so its a big insert. Others, like Iscar, Seco, make narrower inserts/blades. The GTN-3 takes a big bite but it will go through most materials without much effort.


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## Dan_S (Oct 30, 2015)

you could use it on a 7" machine if you wanted. The only thing the really maters, is if you can get in on center, and that the machine is capable of taking a cut the width of the insert. GT(R,L,N) size 2 inserts are only 3/32" wide.


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## Chipper5783 (Oct 31, 2015)

I use that style, with the 1/8" insert (the blade being a bit thinner).  It is true that a wider blade will allow a deeper part off, but a wider blade is more likely to chatter.  To start with, get as narrow a blade as you can, that will plunge as deep as needed for the type of jobs you do.  For the 14" lathe, you should have no trouble with a 1/8" set up.  As Dan_S pointed out, you can use that blade on even a pretty small lathe - it really depends on soooo many factors.

What sort of work are you parting off?  A narrow blade will be quite forgiving of a less than ideal set up.  You may get a wider blade later, but the narrow one will always be useful.


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## maker of things (Oct 31, 2015)

I don't have a specific project in mind.  I started thinking about this after I launched my hss blade parting off a 2" aluminum round.  I think that was largely due to the fact that I ground the blade to be a "right" and I think the blade curved as I plunged until it grabbed and pewww.  Not overly impressed with the "standard" import blade holder that came with my set either.


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## maker of things (Oct 31, 2015)

Chipper5783 said:


> - it really depends on soooo many factors.


That does make it difficult to solicit advice.  Especially when I don't know what those factors will be.  Well so long as I am at least barking up a tree in the right forest that's a good start.  Now I off to order the one and only version of blade and insert that exists...


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## mikey (Oct 31, 2015)

I'm not sure what factors Chipper5783 is referring to but your lathe is large enough and rigid enough to handle a GTN-3 inserted tip parting tool provided you have the proper holder for it. Nothing to be confused about if parting is all you intend. If you need to use it for grooving or making thread reliefs then you may want a narrower blade but it will do just fine for parting. This blade is very rigid as long as it is perpendicular to the work and on center. Holders for this blade are available from Aloris and others. 

If you need a narrower insert, like a GTN-1 or GTN-2, then just be sure you have a holder that will get you on center and you're good to go. If you want to use other types of inserted tip tools then, again, you need the proper holder. The GTN type blade is an old design. More modern parting tools use different shapes and screws to hold the insert in place. 

You can also use a HSS tool  but I suggest a square grind instead of an angled one.


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## Thad (Dec 29, 2015)

Iscar recommends running a little above center if possible grooving and part, their cheat sheet for it is
 width of insert X .031 +.001 = max above centerline


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