I only use carbide for specific jobs. I particularly like the polished DCGT type inserts for light alloys but with only two cutting tips they’re not cheap. For hard materials I use the double sided triangular TNMG style inserts which give you six cutting tips. I’m only using a small lathe though so mostly use a HSS Tangential Tool for general turning.

First, I am assuming that your tool size is 12mm square, from your other thread. You could probably get WNMG 06 inserts for this shank size. They are trigonic, with 6 edges per insert, which is very economical compared to the 2 edges on the CCMT 09 in your other thread.

I have just looked for 12mm tooling for this type of insert, and unfortunately, the smallest size was 16mm square. With a mill, that size could be reduced to 12mm in height.

Edited By old mart on 14/09/2020 13:54:11

Depends on the type of job and size of the holder.

Broadly speaking, inserts work best driven much harder and faster than HSS, which means it helps to own a powerful fast machine. Chip-breakers don't work properly at slow speed.

However Inserts are convenient and worthwhile on hobby machines, but it's necessary to experiment for best results. Older slower machines may be the exception, demanding HSS. Actually HSS has several advantages, so don't dismiss it even in an insert workshop. Easier to get good finish, can be ground into special shapes, and cheap. Having to sharpen it is the main disadvantage.

Having said that, I must be at least 80% carbide in my workshop. Mostly CCMT 060204, (rhomboid) for small work in steel, or CCGT 060204 uncoated for non-ferrous (though the sharp point is good on mild-steel at slow speeds.) I have a holder that can apply the obtuse angle for facing, so all 4 points get used.

For medium sized turning I have TCMT090904 triangles, and for heavier work in steel SCMT09T304 (square) and WCMT06T308 (trigon). Round inserts are jolly useful too, and of course parting and threading inserts to suit their holders.

Several pros and cons with insert shapes. Aluminium prefers sharp rhomboids, but the point is delicate when used on steel. Rounder tipped rhomboids for steel also work on Aluminium and Brass, but may be fussy about depth of cut and feed-rate. Triangles are strong and squares very strong, which makes them good for removing steel at high speed and dealing with awkward metals like work-hardening stainless. The mix of jobs I do usually means heavy facing and turning with SCMT09T304, and turning with WCMT06T308 switching to CCMT 060204 or HSS for anything requiring delicate finesse. The other inserts are used less often, but they do good work when the job calls for them. Your requirements, materials and machine may suit other inserts, but I bet most people do OK with CCMT060204, at least as a starter for ten.

Dave