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.
Is the idea for the thread to grab the 16 ga material in the minor diameter
and sort of wedge it, or to thread/cut into the material? Apropos of the
latter, are chassis screws viable? Still made?
Are sheetrock screws a no-no? I like coarse SR screws, bec they seem to have
a large root/major diam ratio.
Sources for the "right kind" of fastener for this app?
As a sort of perspective, screwing into a wood doorframe seems much more
secure than screwing into a metal doorframe, bec well, you just have more to
My goal is to screw into a metal doorframe and come as close to the
"secureness" of fastening into wood.
The loads that I mentioned will be on the order of bodyweight, and not
static loads, but dynamic. So I also worry about loosening in the metal
frame attachment, which would virtually never happen in wood.
I'm hoping there is a screw design that perhaps specifically addresses these
I assume this is for hinges or the like, the few frames I've seen have
had plates welded on and were drilled and tapped. Usually supplied as
a complete assembly, though, door+frame. If you're trying to mod an
existing installation, threaded inserts are probably the way to go,
although not really super-positive for really heavy loads. They CAN
loosen up given enough provocation. Then they're a lot of fun to
drill out. Welding backing plates followed by drilling and tapping
would be positive for heavier stuff. Then all you have to worry about
is tweaking the frame because it won't stand the load. Eventually,
you end up with a door that's heavier than the wall supporting it,
then the bad guys just drive a stolen Suburban through the wall in
reverse and take their time picking things over.
It's called aircraft technology. There are riv nuts and all kinds of solutions
out there. All of them spread the load across a
large area. EBay is your friend. Consider a doubler and pop rivets. Cheap dirty
and very strong.
frames? At least I think they are 16 ga....
the major to the minor diameter seems kind of small,
and sort of wedge it, or to thread/cut into the
large root/major diam ratio.
You _can_ do it without welding and without special fasteners, but it
requires a bit of ingenuity, some epoxy, and some not-so-friendly (read
this as frustrating) work through a small hole in the frame.
Say you wanted to put two bolts into the frame about 3" apart. Drill
them, and de-burr the inside edges -- you'll want the inside smooth.
Using your bolts as guides, epoxy the appropriate nuts to the appropriate
washers, and let them cure.
Drill a third hole between the others just a tad larger than the diameter
of the washer for that bolt. Smear some more epoxy on the open face of
one of the nut/washer assemblies. With curved forceps or just a curved
wire and magnet (glued to the end!) hold the washer the inside of the
buck while you screw in and gently tighten a bolt. Do to both. Prepare
yourself for losing one or two down into the cavity (DAMHIKT). Let the
epoxy cure, then remove the bolts.
Be gentle when first starting the bolts in again so that you don't break
the "backer nuts" off the inside wall.
"Lloyd E. Sponenburgh" fired this volley in
I could add that if you'll be removing/re-attaching the item any time in
the future, blowing some Great Stuff foam into the buck through the access
hole will help assure that the nut are still where you expect them to be
[ ... ]
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
This one claims to be a rivnut, but is really a different style:
Here is one style which is real, but rather large and somewhat
Here are some metric (M6) ones in aluminum:
O.K. *here* is the proper kind of tool:
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. :-)
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.
All inneresting responses, but the nature of this attachment requires simple
screwing, no fancy stuff.
I'm pretty sure I'll be OK strength/shear-wise with regular sheet metal
screws, just want to make sure they don't loosen with
If worse gets worser, I was thinking of using a silicone seal/loctite type
ditty with the screws.
I guess I can make the rounds of Thomasnet.com, but goddamm, I hate talking
to salespeople, and I'll proly wind up with 5,000 samples I'll have to
organize, since I can't bear to throw shit away....
How does a coarse sheetrock screw "rate" as a sheet metal screw? In
principle, they ARE sheetmetal screws, at least when used with metal
Innerestingly, according to a thread a while ago (comparing fine thread to
coarse thread SR screws), the fine thread are what are used w/ metal studs,
whereas I would have predicted the opposite.