[bsharp]

Looking at general tips on machining Inconel. I do all types of machining and have quite a bit of experience machining 4140, 304 SS, 1045 and A2. From the videos and little I have read online about machining it I gather it would work similar to 4140 and 304 but a bit slower. I normally trochoidal mill using ether indexable or SC end mills and coated cobalt rougher's on 4140 and 304. Because chromoly and stainless surface harden I normally run it all dry and slow. Drilling I usually use cobalt drills and slow speed with aggressive feed.
If any one has experience doing custom work with this stuff I would be interested in hearing any tips you have. The stuff is a little pricy to just buy a piece to play around with.
Thanks in advance.

[RCaffin]

The stuff is a little pricy to just buy a piece to play around with.

But that is what you will have to do, eventually. Try for some scrap maybe?

Cheers
Roger

[ERUS]

Mill or lathe? I have more experience on the lathe end. Mostly with 718. We run a lot of production Inconel. Inconel has a lot of nickel in it. Can't run dry. Work hardens worse than 300 series.

Nasty stuff. Makes a beautiful finish.

Roughing I run about 175 - 250 sfm. Maybe .03" to .05" depth of cut. 0.006" - 0.008" FPR.

We have tried every manufacturers special inserts under the sun and can still only get about 8 parts out of one insert edge. Best option we found are the new mini DNMG and CNMG offered by Tungaloy and Iscar. Iscars mini C works the best so far.

Cobalt drills work fine in inconel. You don't need carbide drills.


Where do you live? I can send you some little scrap rounds.

[ERUS]

Just to add for a 0.25" drill. 300 - 350 rpm, 0.001 - .002" Feed per tooth. 0.4" depth. Cobalt. Drill will usualy last 50 holes or so.

[RCaffin]

Cobalt drills work fine in inconel. You don't need carbide drills.

That's the bit which puzzles me. I machine titanium alloys, and the same is said for that metal.
But if Co-HSS works fine for drilling, why doesn't it work for milling? Why does carbide die so quickly? Yes, sure, drilling is not the same as milling, but even so it still seems a bit strange. Are people still pushing the carbide milling tips too fast through the metal?

I was drilling some 6Al4V and accidentally set the spin too high. The spindle power rocketed up. I cut the speed down a little bit, and the power dropped dramatically.

Cheers
Roger
EDIT: carbide milling tips = carbide inserts

[mkd]

That's the bit which puzzles me. I machine titanium alloys, and the same is said for that metal.
But if Co-HSS works fine for drilling, why doesn't it work for milling? Why does carbide die so quickly? Yes, sure, drilling is not the same as milling, but even so it still seems a bit strange. Are people still pushing the carbide milling tips too fast through the metal?

I was drilling some 6Al4V and accidentally set the spin too high. The spindle power rocketed up. I cut the speed down a little bit, and the power dropped dramatically.

Cheers
Roger

HSS-Co DOES work fine in Ti for milling. Cuts i've done in the stuff might make your HSM fanboi's head spin.
why carbide die so quick?....cause you're doing it wrong.(nuts)

what are carbide milling tips?

ceramics are prolly best for milling Inconel.

[RCaffin]

why carbide die so quick?....cause you're doing it wrong.

I was referring to someone else's comment there. I have not had carbide fail on me on Ti in production work.

I have tried using narrow HSS-CO for parting off Ti tubing. Not a lot of joy, but perhaps I was going too fast. I switched to plain carbide and had zero problems thereafter.

Ceramics for Inconel - a good thought. Thank you.

Cheers
Roger

[ERUS]

My opinion on it.

The surface contact is lower on a endmill versus a drill. The cutting edge of the endmill heats up faster than the cutting edge of a drill due to the cutting edge having less mass to dissipate the heat. Carbide can take the heat with a adequate cooling system.

Edit - HSS does work, but for how long versus carbide? The thermal conductvity of inconel is extremly low. Titanium as well. Since the material can't absorb the heat fast enough the heat concentrates on the cutting edge of the tool. Pure copper is 357 W/(m·K), pure aluminum is 212. Inconel and titanium are 14 and 20, respectively.

The reason our inserts fail so fast is due to the geometry of the part and the nature of inconel. The chips stay one continuious string and build up in front of the insert between the edge of the insert and the back face of the part. When the tool gets to the back face of the part it then has to cut through the continuious chip it has just pushed there. This usually knocks out the inserts above the tool nose radius. We tried a special kennametal insert that was notched out above the TNR to specifically allow for this, but it still happened. 32 parts per roughing insert. Iscar mini-CNMG. 50 - 250 part production runs.

Roger - Check out some of the Iscar endmills. Its a 1/2" 12 flute. The cutting geometry is much different that a standard endmill. The flute depths are very shallow and the cutting edge is much thicker than a standard endmill. We've used them for Ti- Ebay Listing

[RCaffin]

ISCAR ECI - um ... yeah, VERY different!
That needs some thought.
Thank you!

Cheers
Roger

[mkd]

erus, cool part!!!

fraisia has some cutters on you that are maybe like you are saying:

Inconel 718 Dynamic Milling - YouTube

[RCaffin]

Interesting: 820 RPM!
And LOTs of coolant.

Cheers
Roger