Helical Bore Milling

[Ginger_Ninja54]

I have to produce a series of dia' 70mm (proper measurements!! haha!) bores in P20.
They are 81mm deep, blind, flat bottom.

I dont really want to have multiple operations, but was thinking 20mm drill to depth, then dia' 40mm inserted facemill to helical mill.
(or ideally, mill from solid)

My question is, what is the best insert shape for this?
I've got to buy a new holder anyway.
probably go for a shell mill fixation, with a long series holder to suit.

I have 15k rpm.
high pressure TSC
very rigid fixture.
5-axis Mikron HPM1150
HSK63-A 'backends'


Any suggestions gratefully received.

[Bent]

Make sure that the tool can ramp . Very few facemills can. Helical milling works very well IMO a round insert is god because the edges are strong. GET RID OF THE CHIPS or they'll ruin your tool.

Bent