[keen]

I find this work challenging. If the settings and cutter are not right the cutter will soon break down and self destruct!

The pics below show a 100mm bore cut in 56mm thick 4150 H/T steel. I cut through 28mm from each side. I have found that a small negative top rake needs to be lapped on the cutting edges for it to last the distance. Without this 'Eating' its own swarf and the chatter (difficult to entirely avoid especially on a light NC mill) will cause a sharp edge to break down quickly in tough steel.

[dertsap]

you'e be best off using a coated variable flute end mill with a slightly radiused corner .03" or so

[keen]

you'e be best off using a coated variable flute end mill with a slightly radiused corner .03" or so

I should have mentioned I dont use new cutters for this work - I diamond grind by hand about a 15 deg chamfer on a blunt carb cutter. Also makes the neg top rake lapping easier also.

[dertsap]

I should have mentioned I dont use new cutters for this work - I diamond grind by hand about a 15 deg chamfer on a blunt carb cutter. Also makes the neg top rake lapping easier also.

if your doing it for money and production then I suggest getting the right tool for the job , it will pay for itself , if its for hobby then what ever works
the collet probably isn't helping with the chatter , if you have a solid holder then that would probably help

[keen]

if your doing it for money and production then I suggest getting the right tool for the job , it will pay for itself , if its for hobby then what ever works
the collet probably isn't helping with the chatter , if you have a solid holder then that would probably help

dertsap are you using a tormach?

[dertsap]

no

[Geof]

It is called "honing", and yes it does prolong tool life.

What you can also do is rig up a powerful airblast to blow chips clear to avoid recutting.

[keen]

It is called "honing", and yes it does prolong tool life.

What you can also do is rig up a powerful airblast to blow chips clear to avoid recutting.

Hell Geof - if I used an air blast on an open machine I would have chips for miles!