Spline help - error in interaction with hub 1

[RJRoberts]

Hi all,

First time post here so go easy on me!

I have an issue with a current build I'm working on. There was a CAD error which has resulted in hubs being manufactured with an identical spline form to the driveshaft. Obviously this has resulted in a transition fit and thus making the 2 parts not viable to fit together. What options do I have? Can I get an oversized broaching tool made to clean out the excess material? So far possible resolutions are;

1. Try to use current driveshaft as the broaching tool, creating a lead in to aid location
2. Heating and freezing mating components (very difficult to do as bearing is located right next to the splined area and will likely distort
3. Looking at a tool to individually remove material from each tooth

Any suggestions? Need to do something asap! The hub is EN16T and at this point I'm not sure on the driveshaft material. Any help would be appreciated.

 

[gearcutter]

More info would be helpful.
Spline data, drawings, material/heat treatment specs and parts quantity.

 

[EdStainless]

Can you remove the part with the female?
If so see if you can find someone to slurry (ExtrudeHone) hone it.
This should be able to take out enough material for a fit without changing the profile much.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[RJRoberts]

See attached drawing of the spline, both internal and external spline will be done to this drawing (due to the error). The driveshaft is a GKN part unsure on material spec at this point.How would you hone the profile? Parts aren't together at them moment. For these builds it doesnt matter if they never come apart again. The spline's were wire cut.

 

[MikeHalloran]

I suppose the next unanswered question is, "How many do you need to fix?".

My friend Fred used to accurize M1911s by squeezing the slides in a vise so they were a little tight, then assemble them with non-fluoride toothpaste, and run them back and forth by hand until they loosened up just a tad. Of course, he only did one at a time, and didn't really care about the uncertain number of hours of hand labor involved.



Mike Halloran
Pembroke Pines, FL, USA

 

[gearcutter]

If both the internal & external profiles have been machined to the same dimensions; there aren't all that many options for you.
Due to tooth-tooth spacing errors as well as profile error; the transition fit you describe is more than likely going to be an interference-type fit for the majority of the contact.
Also, the flanks are not going to be the only point of contact. The major & minor diameters will also be making contact.

You still haven't told us the heat treatment & material specs or the quantities involved.
We also need to know how these parts were manufactured.

 

[RJRoberts]

You still haven't told us the heat treatment & material specs or the quantities involved - EN16T, machined from solid, no further heat treatment

We also need to know how these parts were manufactured - As above, machined from solid. Driveshaft from GKN I cant get hold of the tech specs yet.

I have 12 in this condition. I agree with the interference fit. The spline was cut using EDM, would I have any chance going to the supplier and seeing if they can reset the pieces and re cut?

 

[3DDave]

Ouch.

Getting the parts set up again is going to be a bit painful, but may be the most predictable outcome. At least with EDM you won't have tool deflection. I expect it to cost a bit more than the first go around as the entire surface has to be recut, plus it has to match the location and orientation close enough not to be cutting 'air' which will leave mis-matches. Other than that it's up to the skill of the EDM operator.

It may be the parts are close enough that crocus cloth and a power file setup would polish the part to fit, but there is less control and getting the fit uniform will not be guaranteed. You could make a tooth=shaped support for the crocus cloth to try to maintain the shape, but it's tough to create root clearance that way.

The match-polish method is OK, but it also will alter the shaft spline so any replacement with a correct hub won't fit quite right. I don't know if that's a problem, but it should be noted in the as-built list if that's what is done so any future repairs aren't mystery items about unexpected clearance.

I think the extrude hone won't be the best solution as it tends to smooth off the high shear points, which won't be in the recesses. I expect it would open up the tip diameter and round the tips but not help with the sides or the root fit. If it was cylindrical extrude honing would be a good answer.

Best of luck.

 

[MikeHalloran]

You could look into electropolishing.
I think the parts can be masked, e.g. with a strippable coating, so the electrolyte only touches the splines.
I think the electropolisher will have to make an electrode, basically a slightly undersize mating part.


At some point you are better off painting the mere dozen parts purple and mounting them on nice walnut plaques to give away as desk ornaments.


Mike Halloran
Pembroke Pines, FL, USA

 

[gearcutter]

As you seem to be unable to provide all of the info that's been asked for; the only thing I can suggest is to re-make the parts. With such a small quantity involved; I doubt that there would be a solution that would end up being more cost effective than simply re-making the parts.

 

[RJRoberts]

What information haven't I given?

I have spline info for the hub and shaft,

Hub
photo uploading

Shaft
image hosting over 10mb

I have been in touch with a few spark erodes who believe they will be able to do it without too much trouble so that's the route I will probably take.

 

[gearcutter]

What information haven't I given?

Perhaps you could re-read the posts.

The spec is calling for a lead correction of 32', +/- 4'.
I don't know of an EDM that could replicate that, let alone applying it to a profile which has, no doubt, already been machined without the correction.

 

[RJRoberts]

I'am surprised by that, the driveshaft CV spline is from an Aston Martin, a GKN part.