Re: Rivnut Tool
 

When you machine 6063 Aluminum the chips tend to reform and stick on your end mills and other cutters.

Re: Rivnut Tool
 

The longer (.225") rivnuts arrived a couple of days ago, and I spent some time today in testing. I'm planning a white paper to be out before kickoff, but here's the gouge:

• I began by inserting the machine screw "dry", and tightening with a T-handle (I did not use arm strength; with limited hand strength, I can get to about 2 ft-lb with a T-handle). Unless that failed, I then disassembled the test unit, sprayed the threads with WD-40, and re-assembled for higher torque tests. All tests utilized new (or lightly stressed) stainless 10-32x1" allen-cap-head machine screws; I expect these to be a bit stronger and more consistent than "plain steel" machine screws.
• In 1/16" 6063 aluminum, I only tried the short rivnuts, because the longer ones would clearly not grip. The maximum torque supported with lubricated threads was 4 ft-lb, which theoretically corresponds to a clamp load of over 2200 pounds, which should have broken the machine screw. However, the failure mode was the rivnut pulling out of the aluminum through a "volcano" deformation.
• In 0.1" versaframe tubing (6061), the short rivnut performed sililarly to the 1/16" case above. The long rivnut secured tightly originally, and supported a torque of up to 6.5 ft-lb for several full revolutions. Failure was due to shearing of the machine screw near the head. After failure, there was definite visible deformation of the surface (~1/16"), and the rivnut was loose in the hole after failure of the screw.
• In 1/8" 6061-T5 C-channel, the short rivnut pulled out easily with about 2ft-lb of "dry" torque (provided by an Allen T-handle; torque estimated by hand). Note that in the preliminary test, I had applied far greater clamping force to the tool than should be required; in this case, I applied forces similar to those necessary to clamp in thinner material.
• In 1/8" 6061-T5 C-channel, the longer rivnut supported a maximum torque of about 6 to 6.5 ft lb. Failure was due to shearing of the machine screw, and there was no discernible deformation of the aluminum.
• In 1/8" 5052 plate (particularly, an AM-14U2 end plate), the behavior closely matched the 6061-T5 C-channel above in both cases.

Bottom line: Use the longer (.225) rivnuts in 0.1" and thicker material. TBD if a spacer or gusset will make mounts in VF thick wall tubing more secure.

Caveats: Due to budget limitations, we decided to try rivnuts this year in a very limited case. As we use 10-32 bolts for the majority of our structural work, this was the single thread we decided to experiment with this year.

Thanks. I have noted that sometimes holes drilled in 6063 are not as large as the drill bit would indicate; I presume this is somehow related to "gumminess".

Re: Rivnut Tool
 

Geetwo,

Help me understand your test. It seems that you are torquing the screw in the mounted rivnet to see when it will fail/stripout, is this the case?

Considering that the recommended torque for a typical 10X32 screw application is in the 30 In Lbs range, reaching from 48 to 80 In Lbs in most of the material is fairly impressive. http://www.federalscrewproducts.com/torque-chart.htm

Re: Rivnut Tool
 

Yes. As described several posts above, I was using a 1/2" nut and three washers against the stock so that I was pulling on the rivnut, not simply tightening against the flange.

I had already noticed that the stainless machine screws supported several times the rated torque, even a good bit over grade 8. What I found even more impressive was that all of the shear failures occurred at the same torque to within about 10% (my measuring precision with this tool at that torque). Further the torque on the threaded portion was probably quite a bit less than the torque I was applying, due to friction between the head of the screw and the large washers.

Re: Rivnut Tool
 

Testing is fun and you can learn a lot. Have you looked at the published ratings?
http://www.cardinalcomponents.com/as...properties.pdf

Like Clint mentioned fasteners under 1/4" will generally be measured in in/lbs rather than f/lbs.

Understand that the torque charts are a guide for a properly torqued fastener. These are within the working limits of the fastener. As you've discovered the shear point is quite a bit higher and material plays a big part.

I would think that if your seeing fastening system failures it is likely due to poorly designed joints and/or improper fastening system selection. Of course that's assuming proper installation. ;)