Pie jaws for rings.........what to expect?

So in all my years I have never really used full pie jaws on ring shaped parts................I have some 7075 rings(a gear of sorts) 3/8" thick, 4.75 on the OD and about 3.75" on the ID..............right now they are slugged, OD turn, ID roughed and some material is left to add some backbone for the 1st milling OP(keep it from deforming when clamped). On the first mill OP, holes are drilled(they need to be right on for location) then the part is decked. Once the extra material is removed, they go egg shaped due to getting clamped in the vise. They are then removed(now they are round again), and bolted to a fixture for the finish milling the teeth on the ID and two small holes are drilled for location during final assembly. Cuz they are bolted down, all the teeth are all on location as are the locating pins.........The teeth need to be "round"(+/-.005) more so than on location with the drill holes.....................

What I want to do is cut a long slug, turn, rough bore and part off mutiple parts in one chucking(less sawing and part handling). Now I have 3/8"x4.75"ODx 3.7"ID blanks. (Obviously clamping in a machine vise will make it egg shaped)..................Pie jaws in some 3 jaw chucks should take care of deformation, no? I now can mill all of my features w/o flippin or fiddlin' with boltin parts to a fixture. Just clamp in the three jaw and go...........................should work eh? Or what about some really wide soft jaws(2.5") in the 6" vises? Encapsulate the whole ring? What's some of yoos guys's experiences with similar parts? Maybe I'm just overthinking things?





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I just finished a job with 400 aluminum rings as short as .5" and as long as 2.5". Diameters from 1.5" to 6".

Everything over 3" diameter, I ran in pie jaws and chucked on the ID.

The material was egged out, but they ran beautiful in the pie jaws, and finished with nice concentric diameters.

Your vise jaws look fine. Lots of surface that you’re clamping on.
I don’t think I’d spend the money on pie jaws. You’re not beating the vise handle with a hammer are you?

I’ve held +/- .001 using vise jaws. Just takes a light touch.

Edit. You’ll want to hold your OD’s really close so centerline doesn’t float around.

If your pie jaws are exactly round and matched size wise to the parts they will come out round and on location within .001, or as good as your 3 jaw chuck can repeat. If the blanks vary in size, they will be made tri-lobed to some degree, more or less depending on the size variation.

I like 3 jaw (or 6 jaw) chucks to hold round parts, because the center of the part stays on location even if the part diameter varies or the operator torque varies.

We use lots of pie jaws here, we even make our own for certain jobs. For thin parts like that we have welded a hunk of steel bar or plate to the tops of soft jaws then milled or turned them to shape.

Not exactly recommending this, but it is a thought that came to mind:


Maybe you stand the bar up in the vise and make your part, and cut it off with a slitting saw when done.

G10 P0 X0 Y0 W.425

Go again....


If you don't have a counter - with a "max setting" and a REPEAT function (I doubt most mills doo) then you would likely need a repeat macro so that it doesn't make parts into the vise.

A macro like this has been shown and discussed many times for un-optioned lathes, but would likely werk in a mill?


If I was dooing this - I would likely run the saw around on the inside enough to clear all the teeth, and then saw from the outside when done.

Not sure how you would be sure that the part fell off the stack tho?


Just thinking out loud....
Not saying that it is a good idea...


edit:

Actually - you could just:

G10 P0 X0 Y0 Z.425

And then subroutine it.

If you started mid bar, you could just start at whichever workshift point was appropriate and have all your header info in the sub.

I like that more better!

G10 P0 X0 Y0 Z.850
G10 P0 X0 Y0 Z1.275

Begining of part = G10 P0 X0 Y0 Z0 and you are back to basic.




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Think Snow Eh!
Ox

Pie jaws will work good. I had an ongoing job for rings that were much flimsier than your parts, about 6.5" diameter, the only thing was, as Mud said, bore the jaws to almost the size of your o.d. so you get minimum distortion. My parts were so thin that even then I'd see a tiny bit of trilobing but it didn't matter, you couldn't tell in use. Looking at yours, you shouldn't see that at all.

It's too bad they don't make many sizes of 7075 in thickwall tubing, you sure do throw away a lot of material on those We eventually went away from sand castings to spun cast tube, I don't know if they can do 7075 but it might be worth looking into. There was a place in the Redwood City / East Bay area doing that, they were really helpful if they are still there.

Nice teeth, btw

A bit of missing info is how many of these we are making, for a few hundred I think I would drop a blank in a vise just as you have in your first pic, face it off, chamfer the od and drill 3 holes in the center slug somewhere out of the way. Bolt it on a fixture like in your 2nd op with the 3 holes, face it, drill, countersink, then put in 3 more bolts ( I like flatheads for this ), finish the ID, OD, and remove a finished part without clamping distortion. If there are thousands of them I can make you a good deal on an air chuck new in box.