Machining M2 - Speeds and Feeds - Boring Tip

Recently came across an application machining M2 with CBN Inserts. Thought it was worth sharing. Here is the breakdown:

Job: Finish Bore M2

Material: M2

Hardness: 58-62 HRc

Insert: CDCD51 CBN Insert - Circle $150/ea

Depth of Cut: .002" per side

Feed: .005" per revolution

Surface Feet per Minute: 400 SFM

The Problem: Inconsistent tool life and insert would chip after two parts

Solution:

I am sure that some may have already figured this out based on the radius size of the insert compared to the feed rate, but for those not in the know, here is the fix:

Change to:

Insert: CDCD 51 T DR-50 Insert $50/ea.

Surface Feet per Minute: 300 SFM

Feed Rate: .003" - .004" per revolution

Depth of Cut: Keep the same

Result: Increased tool life by more than 15x to 30 parts per edge and saved over $100 per insert.