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Milling Titanium


Jul 23, 2014
Milling around a boss in Titanium. The outer groove is 1/2" wide x .600" deep is down inside a part starting at 4.125" dp.
Trying to ramp down the groove with a 1/2" endmill but chewed up the corners plus deflected off making boss undersize.
2nd thought was to ramp a 3/8" endmill 1st and then chase the 1/2" but it busted up my edges (.03r on corner)
Any tips on feed and speed down that deep?

Booze Daily

Sep 18, 2015
I think I would try to get most of the stock out by chain drilling around that circle.
Then I would plunge an undersize endmill around to remove what the drill left behind.
Last, I would probably try to make up a homemade trepan tool to finish it to size.

I don't think anything is going to survive any kind of side pressure in this situation so you want all your cutting forces straight up the spindle.


Jul 6, 2006
Hillsboro, New Hampshire
12mm extended neck endmill, four flute. Drill an entry hole so you minimize plunge. I'd try to avoid ramping with that much stickout, only the last bit where you have to.

Chip clearing is important - either air blast or coolant. Don't recut chips, it's bad for cutters.


Feb 11, 2014
120SFM .0025" CLPT if it's Ti6Al4V and you're using carbide. It can be pushed harder, but those are good stable parameters. No idea on ramp angle, sorry.

Might help to have a Ti specific tool.


Jun 23, 2002
Vancouver BC Canada
Hi MacDaddy:
I've milled a good bit of titanium in my time, and one of the first things I do when I see cutters being eaten, is to reduce the cutter surface speed.
Titanium is weird...if you go even a tiny bit over the happy SFM for the cutter, it'll get eaten in a heartbeat but it will happily run all day if you stay just below or right at that happy spot.
Before I learned this, I'd use up 3 or 4 cutters per part; now I can get ten parts out of one cutter.

A complicating factor is that you have an obscenely long stickout for your part...about 8:1.
The best solution I've found for this problem is to reduce my ramp angle so the cutter never sees a lot of side load.
Here's a partially completed Ti6Al4V freaky sex toy (don't ask) where I've ramped down into a slot with a 1/8" four flute carbide bullnose endmill about an inch deep.

My ramp angle is 0.75 degrees and my DOC is limited to 0.005".
The cutter has survived nicely for about 10 of these slots and was used for about ten surface finishing ops too, each of which had the cutter running continuously for about 4 hours.
It's still fine under the scope and I'll bet I can get another half dozen parts out of it before I lose the edges.

So if you can avoid getting too ambitious about making time on the part, you can get away with an awful lot...this is the kind of part where pushing it even a little bit is really counter productive.
So my inclination is to just let the automated robot noodle along at a happy pace and go do something else while it nibbles.
Of course that may really piss off the boss, so you might just have to tell him to go pound sand and then go look for a new job:confused:.


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