[fettersp]

I am currently trying to hard turn right now and have not ran into this issue yet. normally the parts only need 2 grand to come off after heat treating. These parts need about 8 grand for depth and bore on the ID. I broke my poor insert and don't want to break another expensive insert. What would you say is a good amount to take off at a time without the risk of breaking my insert? The inserts are cbn tipped

[deadlykitten]

hy general infos for cbn :
... radius 0.4mm, 080-180M/min, 0.05-0.35mm/revo , doc0.38mm ( avoid doc>0.5 )
... radius 0.8mm, 100-300M/min, same as above
* target lower values

if you wish, please share :
... material/steel type
... hrc after heat-treat
... drawing before & after heat-treat ( and please highlight the places where hrc is being tested )
... cutting specs ( rpm, feed, doc )
... also, maybe these ( is not a must, maybe you have time ) :
...... actuall tools
...... a photo with the setup will help ( so to check the fixture, the atmosphere, etc )

These parts need about 8 grand for depth and bore on the ID

how much is that in mm ?

i guess that by "bore on the id" you mean to increase the diameter, thus X axis

by "depth" do you mean depth-of-cut among X axis ( radial, or diameter ), or do you mean Z axis ( is there a blind hole ) ?

i need to understand where is located the material that has to bee removed, and also if there are shoulders, and if yes, i need to know how you attack those shoulders i also need to know where did you broked your insert ... did it breaked because of cutting forces, or because of chips hanging arround ? it may be possible that insert got weaken when cutting the face, or when entering the cut, because material was not uniform, thus the 1st cut, that "cleans" the surface, has a higher chance to break your insert

please excuse me if it seems that i am asking for too much info, but cbn inserts don't fall from the sky

with a bit of luck, maybe hi-quality carbide will work 4 you, and that is less $$$, compared to cbn inserts ( if it heps, i have delivered a setup in 41Cr4, 45-48hrc, that lasted a few months, changing tools 1-3 times/week, with coolant; i also used cbn in 60hrc, without coolant )

I broke my poor insert and don't want to break another expensive insert.

if feel like it, please write a small motivational story, about how an expensive thing can also be a poor thing if you wish, i will do it too ... no kidding

What would you say is a good amount to take off at a time without the risk of breaking my insert?

if you wish to avoid the risk of breaking, then cut only air / kindly