I just bought some HSS T-15 inserts to try on both my SBL 9 inch and heavy 10. Bought TPG 221/222, DCMT and VCMT. So far I have tried them all on Aluminum, Brass, 12L14, Cr, Delrin and Stainless Steel (gun barrel) both turning and facing. And have on the SB Heavy 10 taken cuts as light as .00025 and can measure it on all the above workpeice's. I use carbide insert's for all roughing in cut's Then just remove the carbide insert and put in the HSS insert then sneak up on the last couple thousands of the finish cut. Have not gotten a smoother or prettier finish. Just as good as any HSS tool bit that has been hand ground on a good bench grinder. I found them doing a Google search for HSS inserts. Very happy and pleased with them and glad I found HSS inserts.
Chet
Chet