Parting Inserts

[ronboult]

I asked the following Q. in another forum but with no response. Can someone help?


What if any are the differences between PTNT 02 and GTN2 parting inserts.

Retailers images show that the shape ( Chip Geometry?) appears different in the pictures but a using a web search has not given me an answer. Foe example see http://www.shop-apt.co.uk/part-off-tools-inserts.html. The PTNT are listed as GTN style whatever that means.

Thanks Ron

[PixMan]

Hi Ron, welcome.

I would say the two are the same system tools. Iscar had introduced those GTx (GTL/GTR/GTN) style parting inserts and blades in the 1970's or so. Since the patent has long expired and they had such and extensive market, other makers went after it.

You are correct that the chipbreaker (top form geometry) is what varies between the different manufacturers. The PTNT02 is the "general purpose" heavy feed rate parting geometry for plowing through to cutoff solid work. The biggest mistake people make with that one is not giving it enough feed. If you look at the GTN 3 NAC35A version, that's a more positive geometry that will work at lower feed rates and leave a smaller burr. I didn't see it offered in 2mm or 2.1mm wide.

That said there are newer, better products out there today if you want performance over cost alone. Other parting systems won't come as cheap, but do secure the insert against a positive stop in the blade or monoblock holder, and offer premium carbide. You get what you pay for....except in AUS. Man, you guys get taken to the cleaners on tooling there for anything other than cheap (Asian) import crap.

Good luck!

[ronboult]

Hi Pixman
Thanks for taking the time to reply to my beginners Q. I have just upgraded my Sieg SC4 8.5x16 lathe to a Sieg Runmaster 13x40 and while I can still use some of the tooling from my little lathe I am taking the opportunity to also upgrade my tooling. On the SC4 I was limited to 10mm and 12mm tool holders, SCLR with CCMT inserts mostly, and GTN 2 & 3 blade type parting tools. Hence my request for info on the types of inserts.

I have started a search for alternative "modern" parting blades with "positive stops". Now I am even more confused. Are you referring to screw down parting holders like MGEHR with MGMN300 inserts or am I completely looking in the wrong direction? There are so many options out there many of which appear to be proprierty designs that I am not sure where to turn. Any suggestions please.

Also my new lathe has a BXA QCTP which with standard toolholders takes up to 16mm tools, and even 20mm with Dorian Tool holders.
I am unsure whether larger (than 12mm) is better or are their disadvantages of larger shanked tools for smaller work?

Ron