What tool to mill this feature?

I've got a job coming up that requires pocketing down 3.275" with a radius in some corners of .188". I'll be using my Tree VMC500 w/ 8k spindle.
What would be the best tool and strategy to tackle this? Material is 7075AL.
Thanks!

The only tool I can think of that will do something like this would be a "neck relieved" style, carbide, asymmetrical flute end mill.
You would need to rough out the pocket using HSM programming, and clean it with the neck relieved style tool.

Just my $0.02,

Doug.

Extra long reduced shank end mill, like this https://www.maritool.com/Cutting-To...r-5.0-long-X-.354-Shank-ZrN/product_info.html

Or this - https://www.maritool.com/Cutting-To...r-4.0-long-X-.281-Shank-ZrN/product_info.html

Plunge mill it.

I recognize that part. Are you getting them as already turned and threaded parts and just doing the milling?

Josh

I'm starting from scratch.

That's interesting. They wouldn't happen to be for an educational institution, would they? I ask because the local college asked us to make a bunch of parts for the indy car team, one of which was that very same part. The company I work for only wanted to donate a weeks worth of machine time, so I ended up just doing the turning work and they said that they'd handle the milling work. I too was stuck with the dilemma of how I was going to do that feature, but ended up not needing to because I ran out of time. I was initially planning to find a reduced shank 3/8" end mill as has been suggested.

Good luck.

Josh

Mr. PishPosh said:

That's interesting. They wouldn't happen to be for an educational institution, would they? I ask because the local college asked us to make a bunch of parts for the indy car team, one of which was that very same part. The company I work for only wanted to donate a weeks worth of machine time, so I ended up just doing the turning work and they said that they'd handle the milling work. I too was stuck with the dilemma of how I was going to do that feature, but ended up not needing to because I ran out of time. I was initially planning to find a reduced shank 3/8" end mill as has been suggested.

Good luck.

Josh

Click to expand...

Oh that's funny! We ran some hubs for the Baha team. Which they never used. I found out during that project how much I hated CAMWorks!

Looks like a cnc ram type edm . . . easy job for that. Or wire cut the profile thru and plug as needed.

Red James said:

Looks like a cnc ram type edm . . . easy job for that. Or wire cut the profile thru and plug as needed.

Click to expand...

9X deep, no need for EDM.

Those reduced shank endmills are miles ahead of a fluted tool of the same length. The different in rigidity is
pretty amazing. Probably won't set any speed records, but I wouldn't be worried or be sweating about running a reduced
shank endmill in there.

I'd probably run it with an ER32 or 40 instead of an ER16, just to grab as much of the shank as possible. The biggest
problem is going to be getting the chips out. When you get down to the bottom the collet nut is going to shield your coolant.

I don't think I've ever had a melt down with 7075, so I might try it dry with an airblast. Though I would probably test that
out first with a cheaper standard length endmill first.

Bobw said:

9X deep, no need for EDM.

Those reduced shank endmills are miles ahead of a fluted tool of the same length. The different in rigidity is
pretty amazing. Probably won't set any speed records, but I wouldn't be worried or be sweating about running a reduced
shank endmill in there.

I'd probably run it with an ER32 or 40 instead of an ER16, just to grab as much of the shank as possible. The biggest
problem is going to be getting the chips out. When you get down to the bottom the collet nut is going to shield your coolant.

I don't think I've ever had a melt down with 7075, so I might try it dry with an airblast. Though I would probably test that
out first with a cheaper standard length endmill first.

Click to expand...

A big +1 on Bob's post.
7075 is much nicer to cut than 6061, especially when coolant (or lack of) becomes an issue.
It does not gum up the flutes like its softer cousins.

If I were running the part, I think I would rough and finish at the same levels, before dropping Z to rough the next. (this is semi-contradictory from my first post; bu, I have had more coffee this morning. LOL)
It will keep the rigidity in the part, and keep chatter to a minimum.

Good luck with the part.

Doug.

My eyes tell me that both drawings are way out of proportion!

???


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Think Snow Eh!
Ox

Rough then just plunge the corner with a 3/8" relieved endmill (destiny, helical, sgs, swiftcarb, etc), and then finish the profile. Its a pretty open area, and the radius doesnt appear to go into a full 90 degree wall, so it shouldn't even be that bad.

Ox said:

My eyes tell me that both drawings are way out of proportion!

???


----------------------

Think Snow Eh!
Ox

Click to expand...

OK - I'm seein' it now.

Apparently both the C/L rad and the outter spur rads are both .718R.
Or maybe the other is "The Mystery Rad"?

It is the corner where the outter spur rad meets the wall that is .188R.

Kept seein' lots of replies about a 3/8 mill, but the rad doesn't go all the way around. It gets clipped off at the wall.

I agreed that it looked like the outter spurs were a 3/8"D feature, but the pic Shirley didn't look like it to me.


The 2nd pic is bogus. Not gunna make that feature look like that with round tooling at all.
But the URH view in the first pic does show the secondary rad in the corner of the spur rads, right where the .188R is pointing on the other view.


The RH pic is poorly drawn and the LH pic is poorly labeled, but I get it now!


------------------------

Think Snow Eh!
Ox

Ox said:

......

Kept seein' lots of replies about a 3/8 mill, but the rad doesn't go all the way around. It gets clipped off at the wall.

......
Ox

Click to expand...

Yes that does look like a problem, it does not look like that rad is tangent to to the outside wall.
If it was a way another alternative would be to drill , bore, plus maybe ream the 3/8 holes which I guess to be the driving surfaces, while everything was still solid.
Then cut away the rest.
Finish bore the .718R last as it looks to be the shafts center locator.
I doubt the bottoms need or would even want nice 90 transitions.
All pretty in the CAD, not so good for actual use.

If not tangent as the drawing looks to me:
You could blind broach it with a cherry head but that would not be much fun and the custom tooling won't be cheap.
Certainly could be EDMed if you had very large piles of money to spend.

Easy to draw stuff in Cad and then throw it over the wall to manufacturing.
Everything should be designed/drawn with an eye towards how to make it. Not the other way around.
Bob

CarbideBob said:

Easy to draw stuff in Cad and then throw it over the wall to manufacturing.
Everything should be designed/drawn with an eye towards how to make it.Bob

Click to expand...

And it's only gonna get worse with the proliferation of 3d printers for 'prototyping'.

I'm guessing the non-tangent looking internal corners are just a crappy graphics illusion. If not, the 'student' who designed this should be failed for this class.

There's also the notched tabs on the outside. Floating brake rotor attachment maybe? Eyeball out to me as a smaller radius than the internal, and farther down. But at least they're out in the open. Could be profiled on a 4th or with a live tool if you have the capability.

No fillet radius at the shoulder where presumably a bearing seats. And the whole outer section where the wheel attaches looks awfully thin to me. I'd have put a tapered bore in that to increase the wall thickness at the bottom. But I don't do any FEA so maybe it's fine as is.

Ox said:

OK - I'm seein' it now.

Apparently both the C/L rad and the outter spur rads are both .718R.
Or maybe the other is "The Mystery Rad"?

It is the corner where the outter spur rad meets the wall that is .188R.

Kept seein' lots of replies about a 3/8 mill, but the rad doesn't go all the way around. It gets clipped off at the wall.

I agreed that it looked like the outter spurs were a 3/8"D feature, but the pic Shirley didn't look like it to me.


The 2nd pic is bogus. Not gunna make that feature look like that with round tooling at all.
But the URH view in the first pic does show the secondary rad in the corner of the spur rads, right where the .188R is pointing on the other view.


The RH pic is poorly drawn and the LH pic is poorly labeled, but I get it now!


------------------------

Think Snow Eh!
Ox

Click to expand...

I see your point about where the 0.188 rad joins the wall OX, but the dim' arrow does point to that ''corner'' and not the middle of the larger arc.

I think we may have an incomplete drawing?

I see your point about where the 0.188 rad joins the wall OX, but the dim' arrow does point to that ''corner'' and not the middle of the larger arc.

Click to expand...

That was my point.

I think most of us at first glance is ass_u_ming that the .188 is for that secondary rad (cloverleaf?) when it is actually for the corner only, and the cloverleaf rad is not spec'd on this drawing at all.


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Think Snow Eh!
Ox

I only dimensioned a few things to give a sense of scale. I wasn't too happy with the model I rec'd from the student... Originally there was no radius in the corner at all...

The feature is for a three lobed axle shaft to fit in. From what I gathered talking to the two students I dealt with, they don't do any original designing, they just take the previous years design and modify it slightly to make it "theirs".

I'm guessing this is a plunge style tri-pode (or tripod) drive hub for an FSAE car? I'm siding with the guys who aren't thrilled with the drawings, both from a "makeability" standpoint and for basic design:

1) Bad stiffness continuity at the transition from the wheel mount flange to the tri-pode/bearing mount section. A more gradual transition would lower stress concentrations at the highest loaded area. And considering they're likely using a heavy bearing assembly from a FWD car for the hub, this is a poor area to try to save weight.

2) Lots of wasted material with that thick disk that's leftover just inboard the (1) thinned area. All it needs to be is a very thin section to keep dirt out, a sheetmetal diaphragm could have been pressed in afterwards to do this. Would also make the inside geometry a snap for wire EDM. Maybe RTV a slip fit disk so you don't scratch the bore, but a reduction of diameter just for the disk press distance might be better.

3) Aluminum, even 7075, sucks for rubbing and point-loading, which is what's happening with the three drive bearings. Even hard coated, it's really only acceptable for a disposable racecar part, and the premise for FSAE is a low cost, easy to maintain autocrosser design (so you should try to avoid lifed parts). And if the whole hub is hardcoated it can increase the risk of cracking at the stressed section in (1).

And the drive surfaces should be very uniform and closely held to minimize bouncing or binding of the drive bearings - do they call that out?

4) No real argument with the drive bobbin area for the disk brake, but I'd like to confirm their bobbin design is reliable and safe given that they don't leave much room for a flange diameter. And how are they planning assembly?

I supported a local FSAE team for a couple years, I would have tried to guide the student towards revising this part.