Need Help!- cutting speed and force required to cut 4140 with HSS

[Aquatic]

I need to cut 4140 pipe.
OD - 137.6mm
wall thickness - 18mm

With the beautiful piece of engineering you see in the attachments.
It has 3 HSS blades(62-65HRC) that rotate out on pins. They are driven by a hydraulic piston down the center on a lever system.

What I need is an RPM and a cutting force (which I can translate into required hydraulic pressure) to cut through the pipe.
The blade at their widest measure Ø138mm

Can anyone help me with a place to start.

The main problem is it is DEEP down a hole so no visuals. Only a RPM and pressure guage

Cheers
Craig

[BobWarfield]

If it was a single point boring head, you'd be running it at approx 50 rpm. Power required, which you can translate to a rough force estimate would be 0.0207 KW.

Sure you wouldn't rather use carbide cutters? Should be pretty easy to figure some lathe inserts that can be installed on the swing out cutters. That would make your rpm more like 400 and the power required is now 0.1775 KW per cutter.

For 3 cutters instead of a single point, the rpm will be the same. Power will be a little less than 3x, but assume 3x for the sake of conservatism. You'll want to consider how the 3 cutters will interact too:

Are they all cutting along the same annulus, with each one cutting deeper like an endmill? Are they staggered along the bore with each a different depth?

My rpm and power computations were done on G-Wizard and assumed an 0.1 mm depth of cut.

Cheers,

BW

[Aquatic]

Thanks Bob

The reason for the HSS was the instability. The body of the cutter has about 12mm a side movement. So the blades will have to guide and cut.

I have the design for a set with carbide inserts all ready for machining.

Thanks again for the help. Will let you know if it worked

C