GTN Parting Tool Interchanability

[Allan]

New Years Greetings.

I have a recently acquired parting tool that I tried for the first time yesterday. It uses what I think are GTN series inserts. The tool says S=5 so I assume it is GTN 5. It came with one insert, well, ah...inserted.

When I began parting some 1045 it chattered like crazy at 90 RPM. So I got a little more aggressive with in feed and things went swimmingly until about 1/2" in the insert snapped without warning. Was using lube brushed on.

In looking for a replacement insert it quickly became obvious that the set of inserts that came with it are wrong- double ended.

So this is all a long way around to ask about the interchangeability of these inserts. When I looked up specs on the inserts they say that a No5 is .2" wide. The one I was using was nowhere near that wide. Are the inserts all the same dimensionally apart from the width? Can I use a No 3 insert? Or is that part of the reason that the original broke? The one that was in there is the same width as the tool where it is clamped in.

Obviously this is my first foray into bewildering world carbide part off tooling. I have always used HSS up until now with not too many interesting events. Seems to be calling back to my roots.

 

[keeena]

It (only) takes GTN-3 inserts. S-5 is the size of the tool for the bolt (5mm Allen)

 

[Allan]

Ah. I see. Thanks. Some of this information is simple but hard to find. Odd they wouldn't make that distinction on the tool.

 

[Allan]

Although, now that I look at the tool again it has what I assume is the bolt size as 6M- (mm?)

 

[ChazzC]

Although, now that I look at the tool again it has what I assume is the bolt size as 6M- (mm?)

I have a similar 1/2” tool holder, which has “S 4” (and “GTN-3”) on it: as @keeena says, the S 4 refers to the tool size (5mm hex) which fits a 6mm SHCS; mine has a 5mm SHCS, which takes a 4mm hex.


[Had to mill the bottom of the tool holder to get correct center height]

Typically, insert screws use torx head screws, so will have a “T” before the number.

 

[Allan]

Gotcha. This is all new to me. A real rat's nest of information. So many styles and grades and applications and manufactures and.....

Nice that yours actually says GNT 3 on it.

 

[mksj]

It states in the description for that model the insert and the screw, in the picture below on the holder it shows the insert size, so maybe yours got rubbed off. I usually part at higher speed with carbide, although crappy inserts, are just that. I use to have a GTN type cut off blade and bought some generic (cobra) inserts, went through the box like toilet paper. You need rigidity, the holder must be perfectly parallel to the chuck, you need to cut with even pressure and just be careful of a chip getting jammed at the tip or side. I also increase the RPM as I cut closer to the center.

 

[Allan]

Thanks for all that . I have gone through various forums here and watched the recommended video. So I just ordered a box of Iscar inserts based on other people saying quality saves money, it doesn't cost more. I will have to use a dial indicator and make a height gauge. Servants beget servants.