On 2010-06-07, Don Foreman wrote:
On Mon, 7 Jun 2010 09:19:38 -0400, "Existential Angst"
wrote:
Awl --
Yeah, I know, a sheetmetal screw.....
But are there designs esp. good for semi-heavy loads attached to 16 ga metal
frames? At least I think they are 16 ga....
The problem I have with traditional sheet metal screws is that the ratio of
the major to the minor diameter seems kind of small, ie, there doesn't seem
to be enough thread "behind" the sheet metal.
[ ... ]
Sources for the "right kind" of fastener for this app?
There are threaded inserts that you "set" with a pop rivet gun. They
then take standard machine screws of various sizes.
What you are talking about are Rivnuts (originally from B.F.
Goodrich). Ideally, you want a proper setting tool, because it is
tricky to not strip out one using a pop rivet gun.
They are fit into a drilled (or punched) hole, and many have a
key which can go into a punched notch to prevent them from spinning in
the hole if not crimped tight enough. 10-32 uses 1/4" holes IIRC.
Here is a tool on eBay which is incorrectly labeled. It claims
to be a puller -- but in reality, it is the notching tool for the keyed
rivnuts:
250646494046
This one claims to be a rivnut, but is really a different style:
390110729218
Here is one style which is real, but rather large and somewhat
expensive:
330353272486
Here are some metric (M6) ones in aluminum:
290442533133
O.K. *here* is the proper kind of tool:
350362595796
You pull on the mushroom handle to turn the screw CCW, and push on it
to turn it CW. So -- you pull it out, hold the nut on the screw, push
it in to run the screw into the nut. Then you put the Rivnut into the
hole, squeeze the handle (which sets the Rivnut) and then pull on the
mushroom handle again to unscrew the drive screw so you can go on to the
next one. There are adjustments to set for thickness of the metal and
length of the Rivnut, and if properly set, they set the Rivnuts
properly. If improperly set, they can leave it too loose, or too tight
and strip out the threads.
They are specific to a given size -- and this one looks like it is
either 8-32 or 10-32 with a couple of spare drawscrews. You need to
change both the drawscrew and the nosepiece bushing to change size --
though yes, the same tool (with the right drawscrews and bushings) will
cover the range from 4-40 through 10-24 or even 1/4-28 and 1/4-20.
I've got one of each size.
Note that if you have steel Rivnuts in the larger sizes, you
need hydraulic or pneumatic pullers -- but for your task, I don't think
that you will need that, so I did not mention them at all.
This one is explicit that it is for 6-32 -- and it has a price
which I would not touch. :-)
330410557456
Yes -- you can set them with a pop-rivet gun and a long screw with
part of the length turned down to a pop-rivet pull stud, but be careful
not to strip the threads out.
Enjoy,
DoN.
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