Shaping Internal splines with mill good/bad?

Garwood · Dec 13, 2011

Considering using a Mori-Seiki MV-45 mill and indexer as a slotter to cut internal involute splines in a blind hole. The bore is 1.5" diameter X 2" depth in 8620. Low volume part, 5-10 pieces/month.

Would using the mill as a shaper be bad for the machine? It's well made heavy mill, would it do well with light .002" passes?

Any suggestions on making a proper cutter to do this?

Ox · Dec 13, 2011

Ohio Broach actually has a new machine out currently that is basically that.

Not sure what is different about it. They may use lesser pitch lead screws in Z I would like to think?

Prolly a bit diff software too maybe?

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Think Snow Eh!
Ox

Metalcutter · Dec 13, 2011

Garwood said:
Considering using a Mori-Seiki MV-45 mill and indexer as a slotter to cut internal involute splines in a blind hole. The bore is 1.5" diameter X 2" depth in 8620. Low volume part, 5-10 pieces/month.

Would using the mill as a shaper be bad for the machine? It's well made heavy mill, would it do well with light .002" passes?

Any suggestions on making a proper cutter to do this?

I've done things like this. Hand Index Mill. If the the broached "slot" needs to be wide, do a narrower slot on either side and then do the middle. This balances the load so the broach doesn't drift. Since the hole is blind you will need to under cut the bottom of the hole to allow the broach to finish the cut at the bottom. You also need to be concerned about chip "stacking" so you don't bang into a "pack" of them at the bottom.

Just trying to help you avoid all the things I ran into.

You'll need to lock the spindle from rotation.

As far as the .002" chips, I don't see a problem, but take in the width too.

The bearings in that machine are precious, try to keep the impact at a minimum. You could start slow, and after engagement, speed up the down feed, when the "Marbles" are already under pressure.

Best regards,

Stan-

david n · Dec 13, 2011

To ruduce impact on the spindle bearings, you could mount your tool solid to the head and not in a toolholder.

Ox · Dec 13, 2011

Good point - the spindle layout is likely differn't on the one designed for it.

For your few pcs - If you have spindle indexing - you wouldn't need the rotary table.

(Not that I am, or are not reccommending it)

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Think Snow Eh!
Ox

behindpropellers · Dec 13, 2011

Garwood said:
Considering using a Mori-Seiki MV-45 mill and indexer as a slotter to cut internal involute splines in a blind hole. The bore is 1.5" diameter X 2" depth in 8620. Low volume part, 5-10 pieces/month.

Would using the mill as a shaper be bad for the machine? It's well made heavy mill, would it do well with light .002" passes?

Any suggestions on making a proper cutter to do this?

For 5-10 pieces a month is it really even worth the hassle ?

david n · Dec 13, 2011

behindpropellers said:
For 5-10 pieces a month is it really even worth the hassle ?

If the customer is willing to pay for it.

Garwood · Dec 13, 2011

behindpropellers said:
For 5-10 pieces a month is it really even worth the hassle ?

First shop quoted $175 each in qty of 5 so doing in house crossed my mind. Today, different shop quoted same at $70 a piece. Sounds much better.

Dan from Oakland · Dec 13, 2011

As david said- mount your slotting bar on the head somewhere- not in the spindle. A set of spindle bearings will be much more than you can charge for the parts.

--OR--

Gear Tooling - The Broach Masters and Universal Gear Company, Blind Hole Broaching

Dan

Ox · Dec 13, 2011

OK fella's 'splain this to me then:

It has been getting more and more accepted to doo this very thing on a lathe..

What's the difference?

I have no horsie in this here race, just not following the logic here...

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Think Snow Eh!
Ox

scudzuki · Dec 13, 2011

The bearings in a lathe headstock are more substantial then those in a VMC spindle. Add in the substantial mass of a lathe chuck and there is far less shock delivered to the more substantial bearings.

I guess.

Joe

metaltech · Dec 14, 2011

Lathe spindle might be more robust (depends on size, of course) than the MC spindle bearings, but both machine's Z ballscrew bearings are smaller, yet. The ballscrew/bearings are going to see the same load as the spindle.

I know the MV-45 well and don't think it would bother the spindle. But, the problem with that scenario is the spindle is electrically-oriented (by the spindle drive) and isn't solid, but held in place by motor torque. That's not a good place to mount a tool like a broach that needs proper alignment. If you're going to do this, mount it to the head as others have said. Best is spend the $70 at the other shop, I think. When you figure the set-up time for your mill and the cycle time it will take, I don't think the $70 sounds too bad. I'd use the mill to do milling.

Ox · Dec 14, 2011

I guess a lathe may possibly set the spindle brake in this case eh?

:scratchchin:

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Think Snow Eh!
Ox

gregormarwick · Dec 14, 2011

metaltech said:
Lathe spindle might be more robust (depends on size, of course) than the MC spindle bearings, but both machine's Z ballscrew bearings are smaller, yet. The ballscrew/bearings are going to see the same load as the spindle.

Static vs. dynamic though. And factor in the inertial mass of the moving turret/head. In practice the ballnut/thrust bearings are going to be getting it very easy compared to the spindle bearings.

Anyway, I do this all the time in the lathe. Advantage there is that I can clamp the spindle. Trying to do it just with the spindle drive holding the orient position is going to be tricky/impossible IMO.

metaltech · Dec 15, 2011

gregormarwick said:
Static vs. dynamic though.

Care to elaborate?

gregormarwick said:
And factor in the inertial mass of the moving turret/head. In practice the ballnut/thrust bearings are going to be getting it very easy compared to the spindle bearings.

As the broach tip approaches the part, there is very low load on the ballscrew bearings. The instant the tip contacts the part, the load greatly increases. The spindle bearings will react part of the load, the ballscrew bearings the other part. The relatively larger surface area of the spindle bearings will spread the load better than the smaller ballscrew bearings, so I would expect the ballscrew bearings to wear (or fail) at a faster rate. I'm not saying your post is wrong, I just don't understand what your position is. I'm not an engineer, so I lack in the theory. I'll ask my son to 'splain it to me when he gets home in a couple of days. He's a fourth-year M.E. student, and he passed me up awhile ago.

I will contend this much: after doing 30 + years of repairs, I've changed a helluva lot more ballscrew bearings than spindle bearings as a result of usage, or wrecks. The difference to me at time of impact between broaching and a wreck is just the severity of the collision.

You're welcome to school me on errors in my thinking.

bnk08 · Dec 15, 2011

Hi all. This is my first post so please be kind

We use the slotting technique in our Okuma Multus B300W very regualy. And over the last 4 yrs and have had no drama's. We slot both internal keys and internal and external splines using a hss tool ground to the desired shape of whats required. For keyways we use a maximum size of 1/2" hss, so to slot a 5/8" key we use Y axis. Our depth of cut is only is 0.05mm.

adama · Dec 15, 2011

Forget the bearings its all about the width and depth of cut. If the bits sharp and narrow the z axis on a non counterbalanced machine may be doing little more than letting gravity make the cut! A 1/8" wide sharp cutter in a bridgeport spindle will easily take a thou per pass with just minimal pressure on the quill handle. Like less than drilling with a 3/8" drill bit pressure.

Yes static bearing loadings are significantly less than dynamic, but even for precision spindle bearings, on a 40 taper machine, there static load rating is in the tonnes range. Remember shaping is a delicate single lip cutting aplication, not a 50 ton broach press cutting method.

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