Carbide insert number designations?

Does anyone have any info on the difference between APMT and APKT inserts or better yet, what does each letter stand for? I was completely at home with the inserts I used for years, I actually easily understood what each letter and number meant on everything I used like CNMG-432, and all the round, square and triangle inserts, but something seems to have changed with the mill inserts that has left me in the dark. I have bought many in the last year or so that don't fit any of my holders due to not knowing the number system. Anybody shed some light on this one?

Most milling inserts today are proprietary. The letters matter with APMT/APKT/APHT but the following numbers may vary from each maker despite looking the same.

A = Parallogram shape
P = 11º side clearance angle (you'll also find ADxx inserts D= 15º)
M = +/-.005" I.C. size. usually molded not ground periphery
K = -.002"to -.006" I.C. size, usually ground periphery
H = +/- .0005" I.C. size, nearly always ground periphery
T = countersunk for screw, usually 45º to 60º

Here's a useful chart: Insert Designation Chart - provides ANSI and ISO designation code definitions for carbide insert shapes, relief angles, tolerances, chipbreaker codes, hole types, size values, thickness values, radius values, wiper lead angle, wiper clearance angle,

Thanks PixMan and red beard, this helps a lot, one big problem when ordering was size. Somehow the pictures would not be good indicators of size, many times I get tiny inserts that aren't even close to the size I needed. My old method was to keep buying Ebay face mills and Ebay inserts in hopes of someday finding an insert that actually fit one of them, you would think eventually it might happen!

When it comes to that style/shape insert in milling, the sizes are usually given in the ISO (metric) designations. Lets say you had an Iscar 1" end mil that uses 3 APKT130408PDR inserts. A similar APMT/APKT 130408 inset from another maker probably wouldn't fit quite right in the cutter even though they have similar numbers.

It is always best to go to the website of the cutter body manufacturer to look up the cutter by catalog or EDP number and see what inserts they have for it. You can work it backwards and find a good bargain on inserts for your application, then use the maker's website to find what cutters the inserts fit into. One of the problems with this method it that on eBay you will often find obsolete inserts and/or cutters that you should just stay away from buying.

If you don't know you're buying a current product, don't buy it!