Mark,
I guess we are talking about the same thing, but I think this is a design
limitation. Rivnuts are not really suitable for high torque applications.
I have used them for low torque applications, such as holding my wheel
spats (M8 size), or fitting my GPS and radio on the instrument panel (M4
size). I plan to use them on inspection hatches too, and also for all the
engine baffling., stuff like that
Also, it is important to use the knurled part best suited to the material
thickness and type: either knurled body or knurled flange.
When I put them in composite, I generally use Epoxy, just in case.
Serge
"Mark Langford" <n5...@hiwaay.net>
Envoyé par : krnet-boun...@mylist.net
2005-04-22 16:26
Veuillez répondre à KRnet
Remis le : 2005-04-22 16:27
Pour : "KRnet" <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : Re: KR> rivnut question
OZ wrote:
> The "real" rivnut tool isn't cheap and neither is the "simplified"
model,
> but there is a mandrel available such that you can install them using
your
> regular pop rivet puller. My question is, does a regular pop rivet
puller
> have enough backbone to pull a rivnut?
Sound like Serge's tool will work fine, given his experience, but you do
need to be careful. The project I just finished up (at work) required
several hundred knurled rivnuts (which are less likely to spin), so we
learned a lot about them in the fabrication process. Maybe Serge and I
are
talking two completely different kinds, so I can only speak to the ones we
used, which came from McMaster Carr. We cheaped out and bought the
"simplified model" ($170 or so), but I don't see a lot of difference
between
that and the $250 model. The problem with that is if you don't get it
tight enough, the rivnut just spins, and you can't tighten up the bolt. If
you squeeze it too tight, the threads get scrunched up and distort, and
the
bolt binds and the rivnut spins. You'd think after several hundred, you
could get the feel of it, or get it adjusted correctly, but it never
happened. Keep in mind that these guys are not just "Bubbas", they're
well-trained experts who commonly fabricate space, defense, and nuclear
hardware day-to-day. We eventually drilled every one of them out and
welded
custom made aluminum inserts into those holes, and have had no problems
since. These were relatively large rivnuts (3/16", 1/4" and 3/8"), so it
may be that the smaller stuff that we'd use on airplanes isn't as touchy,
but I personally have deleted them from my fastening options list, next
time
I have something in a blind hole that needs threads. Some of these
rivnuts
were $4-5 each, but the bosses we welded in were made overnight for about
thirty cents each on our CNC lathe, and were welded in place about as fast
as you could use the rivnut installation tool, but that's not an option
for
most homebuilders...
Mark Langford, Huntsville, Alabama
see KR2S project N56ML at http://home.hiwaay.net/~langford
email to N56ML "at" hiwaay.net
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