Check my chips

[Skierdude]

I hope everyone had a great Christmas.
I’m machining some 4140 HT for the first time. Milling a flat on some 30mm dia round using an 80mm face cutter with 6 carbide inserts, about 440 sfm. (The face cutter is the only insert tool I have right now). No coolant. Very happy with the finish.
Can someone take a look at these chips and let me know if they are too dark. There’s no heat in the work piece and the inserts are not unduly hot but not having any experience with this material I seek guidance from the wise. Going to try a HSS end mill next but somewhat slower.

 

[benmychree]

Chips from a carbide facemill should be dark blue for steel. for HSS tools, SFM should be around perhaps 60 SFM.

 

[Skierdude]

Thanks benmychre. I’ll you the HSS end mill today and see how that goes.

 

[benmychree]

If you see any blue on the chips, slow down ---

 

[T Bredehoft]

I'd be happy with thous chips under your circumstances. Keep up the good work.

 

[benmychree]

I'd be happy with thous chips under your circumstances. Keep up the good work.

I'd be happy with those chips too, unless one landed on bare skin!

 

[Skierdude]

Yep, once a few of those landed on my bare arm I sure learnt how much heat they were carrying. Got a piece of plywood for a shield real quick.
I read quite a few posts before trying the first cuts on 4140 and it was mentioned that the chips should carry away the heat from cutting. After the first pass I was surprised that the work piece had no noticeable heat.
Still trying to clean up all the chips that the face cutter threw around the shop. I see a curtain for the mill table in my future!