Looking for part swaging advice 3

[DELurker]

I am going to be designing a stainless steel (304) part that will be attached to a piece of spring steel (0.79mm thick). It has been recommended that I swage the two parts together.

Are there any specific design considerations that I would need to take into account in order to do this? I'm looking at using a 2mm diameter hole in the spring steel to take a 1.95mm diameter boss on the end of the part, with the boss being about 1.50mm long, giving me 0.71mm of length (nominally) on the other side to swage with. The extended length, of course, is open to changes to improve the design. The diameters can be made slightly larger (~0.5mm) before they start weakening the spring steel part.

Should the boss have any indents or reliefs to make it easier to swage?

Any advice would be greatly appreciated.

 

[berkshire]

DELurker
send a picture or sketch what you are trying to do.
This sounds more like a squeeze riveting operation than a swage.
B.E.

 

[CoryPad]

How are the parts loaded? Tension, shear, torsion, bending? Environment?

 

[DELurker]

I have uploaded a sketch of the assembly in its undeformed state (

http://files.engineering.com/getfil...8-4110-98aa-456596eed939&file=swagedpart.tif)

For the actual process, I'm afraid that my ignorance of the details of cold-forming forces me to use the terms that I was given. Internally, we've used the terms swaging, peening, and forming (among others) to describe it. Since we're going to have to make about 4,000 assemblies at the start of this project, swaging sounded like the most likely process, since we'd probably have to make a die of some kind just to keep the mechanics from killing me.

For the loading, I've indicated the direction of force on the sketch. The stainless piece is constrained in a hole (slip fit) which will only allow it to translate along a single axis. The last quarter to third of the spring steel is restrained in a slot so that it can push back through the stainless piece.

 

[CoryPad]

Looks like upsetting to me, similar to "bucking" a rivet tail. For rivets, there are semi-tubular ones that allow easy flaring. Orbital riveting is a variant that has some merit:

http://en.wikipedia.org/wiki/Orbital_riveting

Do you have equipment, vendors, etc. already in mind?

Some further information on riveting:

NASA RP1228
MIL-HDBK-5
MIL-STD-403

 

[berkshire]

As Cory says this is an upsetting operation.
My last question is ; does this part F have to rotate after the end is peen ed over. If it does then a tube form would be an advantage.
If not then a straight press with a flat top to swell the stem would work better. And yes you are going to have to make a holding fixture for this.
B.E.

 

[DELurker]

Thank you CoryPad and berkshire for your help so far...

We don't have any equipment or vendors in mind at the moment. The machine shop that has been making the prototypes has been peening them over with a hammer, but we're going to need 4,000 of these inside a short timeframe once the higher-ups pull the trigger on this. Forming that many with a hammer would be ... tedious? Expensive?

As for the part turning, no, the part does not need to turn after all is said and done. I would actually think that turning would be a bad thing (frictional wear on all surfaces).

 

[CoryPad]

A simple arbor press may be sufficient, and certainly better than a hammer.

 

[berkshire]

DE
I do not know what your budget can stand, but for those kind of quantities, a bench mounted squeeze riveter will give faster and more consistent results. If that costs too much, then an alligator jaw squeezer from the same company, mounted on a bench with a home made bracket will work too.
Good luck with your project,
B.E.