Face Milling 6AL-4V - Best approach for a small manual mill

Erin Burke

Erin Burke

KnifeMaker...ish
Joined
May 19, 2003
Messages
1,330
Hey guys.

I've been playing around with 6AL-4V for a few months now... mostly drilling, reaming, and simple slot-milling for inlays. I've been using 0.13" plate, but decided that I'd like to try some 0.15"-0.16" for a new project. Rather than buy the thickness that I needed, I got a great deal on some 0.20" plate off Eeeeebay. I figured I'd try face-milling small pieces to the correct thickness. I'm starting to think that the thicker plate wasn't such a great deal. :eek:

I'm running a manual Sieg X3 from Grizzly without flood coolant. I decided to use a 2" indexable face-mill to take off 0.04". I've had decent luck in the past (with smaller carbide end-mills) using the milling speeds taken from table 11 of the TIMET page. For the larger 2" facemill, however, the speed turns out to be approximately 140rpm. I gave it a go, taking multiple passes with a VERY shallow depth of cut (<0.01" per pass). I ended up galling up the carbide inserts quickly and a rough surface finish... you can kind of see it in this photo.
5636295445_d6e04cf3ee_o.jpg


So what is the best way to clean this up?... and how should I do this in the future (since I have a LOT of 0.2" Ti)? I just bought some re-ground 1/2" carbide end mills, and am thinking about giving them a try... (at about 550rpm). What do you think?

I'm really looking for a clean final finish.

Thanks in advance. Erin
 
6-4 AL-V, 2" face mill, and mini mill don't all belong in the same sentence. I see rebay in your future...

The yield point of that titanium is about 150 KSI, at least 3X most regular soft steel, and it is half as stiff. So cutting 6-4 isn't easy.

The machining strategy to use with titanium is rigid setup (do I see plywood in there?) low depth of cut, low SFM and relatively high feed per tooth (probably .005" in your situation). I think you're probably already doing it "right" and seeing the limitations of your tool. You might have better luck using a high rake face mill and inserts designed for low HP machines. You might remove some inserts to reduce cutting forces (6--->3 etc), reducing your feed proportionately. But ultimately, I don't think you have enough mill to do what you're wanting to do and achieve a good finish.

Sometimes inserted face mills make their best surface finish in a sweet spot depth of cut. .040" DOC is a pretty reasonably number for that, but my 8,800 pound mill would have trouble with that in 6-4, I really don't see that working on a mini mill. I could be wrong *shrug*.
 
Thanks Nathan... I'm definitely trying to do too much with this little machine, but I'm working with what I have. ;)
I've heard it recommended to use smaller mills when working Ti... so I'm hoping that by changing to a 1/2" end mill and upping the rpm I can help compensate for the lighter machine (and lack of a heavier machine's rigidity).
BTW, that's not not plywood... it's face-milled purpleheart. It's very hard/dense/rigid... though not as rigid, I'm sure, as a block of steel. ;)
Thanks again for the info Nathan. I was hoping you'd chime in. I'll let you know how it works out. Maybe next time I'll just bite the bullet and buy the correct thickness of Ti to begin with.
 
Erin, i do it all the time on a similar machine. i too first tried to use a 2" indexable and it was a no go. i now use 1/2" carbide endmill's. it takes more passes but i can easily take .020 per pass if need be. i go between 500-700 rpm. i also have a very rigid aluminum plate fixure that i machine off of.
 
balibalistic said:
Erin, i do it all the time on a similar machine. i too first tried to use a 2" indexable and it was a no go. i now use 1/2" carbide endmill's. it takes more passes but i can easily take .020 per pass if need be. i go between 500-700 rpm. i also have a very rigid aluminum plate fixure that i machine off of.
Click to expand...

Thanks Shawn. :thumbup: Should have figured that you'd have experience with this.
 
I'd rather take a beating than mill titanium to thickness. I understand why you're trying, but it's too easy to buy the stuff in the thickness needed.
 
Don Hanson III said:
I'd rather take a beating than mill titanium to thickness. I understand why you're trying, but it's too easy to buy the stuff in the thickness needed.
Click to expand...

Hahahaha... my poor face-mill inserts sure took a beating. Thankfully they have four sides. I'm kind of anxious to give the 1/2" carbide end-mills a try though.
 
Don Hanson III said:
I'd rather take a beating than mill titanium to thickness. I understand why you're trying, but it's too easy to buy the stuff in the thickness needed.
Click to expand...

I too, try to buy it in thicknesses that i need. but i often make one of's with different blade thicknesses so i generally just machine the titanium to size. as long as the endmills are sharp it's easy as pie.

Erin, dont bother using even slightly dull endmill's for this. it will cause the titanium to bow and give you all kinds of issues. just check ebay and get some good endmill's. wait till you try a hanita varimill!!
 
balibalistic said:
I too, try to buy it in thicknesses that i need. but i often make one of's with different blade thicknesses so i generally just machine the titanium to size. as long as the endmills are sharp it's easy as pie.
Click to expand...

All mine are one-offs, but I take the steel to the surface grinder.;) I do know what you're saying though.
 
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