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The usual procedure for using a Pop rivet involves drilling a hole that will accept the unexpanded shank, and placing a shank-sized washer over the head of the rivet before expanding the head.
In the case of a deep attachment surface, it can be difficult or impossible to provide an orthogonal location
for a washer.
The drill bit in this idea is designed to drill a hole of the shank diameter, for a predetermined depth, and expand rapidly beyond that depth, allowing a Pop rivet to he used in a "blind" location.
The means by which this is accomplished are varied; the simplest would involve a collar attached to the bit, which when it reaches the suitable receiving surface depth would activate a lever on the tip to expand the diameter of the cut.
Means would have to be provided to remove the cut material.
Pop Rivet
http://en.wikipedia.../Rivet#Blind_rivets
For use with this type of rivet [csea, Oct 20 2011]
You mean it's not ...?
http://www.windowbl...nd-People-image.gif
[normzone, Oct 22 2011]
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Wouldn't a rivet with a longer shank be simpler? (actually, I'm not sure if I understand the problem you're trying to solve) |
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The problem is in using a blind rivet to attach a reasonably thin piece to a very thick or inaccessible base. |
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You could use a drill bit that is slightly bowed. Or,
after drilling the hole with an ordinary drill bit, force
in a masonry bit without running the drill. The blade
on the end would make a slight slot in the hole as it
goes in though. |
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Alternatively, use a screw. |
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// normally used washerless // |
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It depends on the application. Some are, some aren't. |
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The requirement is to drill a T-shaped hole. Square corners on the expanded region are important to give the rivet "grip" when expanded. |
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Alternatively, a hole shaped like an arrowhead and shaft would be acceptable. |
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It might turn out to be a two-tool solution. |
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1. Drill blind hole to required depth. |
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2. Insert circumferential cutter and bring up to speed. Lubricant will probably be needed. The head of the cutter beds in the blind end of the hole. Pressure on the butt of the shank would cause cutting blades to expand outwards from recesses in the shank, like a centrifugal governor, cutting into the workpiece. Swarf would be removed by conventional spiral flutes on the shank of the tool, which could be hollow for lubricant injection. |
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This has got to exist somewhere already ... |
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I think it does. I saw an aircraft mechanic using something
like that once, but I have no idea how it works, because he
was on top of a helicopter and I had somewhere else to be
at the time. All I know is that he was punching collared
rivets into a blind space using a very complicated tool, and
I had just long enough to stop and think "that's cool" before
I had to catch up with my boss. |
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Does anybody know what I saw? |
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One could use a grooved bit initially. At desired
depth, feed pointed flexible piece down groove.
Near tip, groove ends in shelf and tip of pointed
flexible piece leaves groove to go laterally. Width
of cavity is controlled by amount of flexible piece
fed into groove. |
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That's clever, but what is the 'flexible piece' made of? |
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Have pawl-like teeth on the drill tip which fold in
when the drill is run clockwise, but catch and extend
when the drill is run anticlockwise. |
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Drill the hole, reverse direction to cut the slot, then
back to normal direction to remove the bit. |
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Another idea: Have bent drill bit, and a guide to ensure the entry point cannot wander. As the drill bit goes in, it gradually drills a bigger diameter hole. |
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And to think all these year I've been tossing bits that did
that... Oh, if only I'd saved them! |
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There's an already-baked non-wobbly version of that called
a tapered (or 'step') bit. |
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Ling, your version would make a cone. I thought
maybe that would not work but the more I think
the better it seems. I did not think fussy tiny
hinged bits in the hurly-burly environment of a bit
head would reliably deploy and so my groove
scheme was to minimize moving parts. But your
hockey stick bit is the simplest of all. |
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Actually, does the hole need to be wider at the
bottom? When a pop-rivet is pulled, the shank
slides into the sleeve, expanding the latter. |
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If the material is hard (steel or concrete), you're
going to create huge frictional forces between the
expanded rivet and the sides of the hole. If the
material is softer (wood, aluminium, plastic), the
expanding base will deform the material, locking
the rivet in place. |
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Either way, I suspect that a simple hole, just large
enough to take the un-pulled rivet, will work well
in most cases. |
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If you want a really high grip, just run a tap into
the hole; the expanding rivet will conform to the
thread and lock itself in place. |
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[MB] but that's a molly, isn't it?
(Edit: Not quite. But it seems to be a "lag shield") |
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Shucks. I was hoping this described a job opportunity for blind pop riveters. |
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Cheer up, Pop. That workman's comp'll come
through any day now. |
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Could a 'butterfly'-style drywall anchor be adapted to this
application? |
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Or a blind drill team sychronised to pop music.
What?... that would be slightly riveting. |
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//Could a 'butterfly'-style drywall anchor be adapted to this application?// |
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Yes, but you'd still need the blind drill to make the special hole required. |
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//[MB] but that's a molly, isn't it?
(Edit: Not quite. But it seems to be a "lag
shield")// |
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No, neither really. A molly is a sleeved bolt,
wherein the sleeve buckles outward as the bolt is
tightened. A lag shield, as far as I can deduce, is
just a confusing name for a rawlplug. |
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My point is that a pop rivet will hold quite
securely in a blind hole in any fairly soft material
such as wood or aluminum (by deforming it as it is
pulled to expand the sleeve); in any hard rough
material such as concrete (by simple friction as
the sleeve expands and presses against the sides
of the hole); and in any hard smooth material such
as steel, if the hole is first tapped (by conforming
to the threaded sides of the hole). |
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(By curious coincidence, our intercalary sibling has
recently returned from Suriname, and reports that
the male Surinamese large-eyed jumping spider
uses precisely this method to lodge its pedipalp in
an unmentionable part of the female Surinamese
large-eyed jumping spider. The forces generated
are sufficient, apparently, to withstand several
hundred G, which is just as well for the survival of
this species.) |
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Pray tell, what thread has a female Surinamese large eyed
jumping spider? By the way, one can't help thinking that
the female has large eyes simply because of the surprise of
the procedure. |
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I shall have to ask him. However, our intercalary
twin is by now about half way to an unspecified
Azore. |
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I have no idea. He said something about "jellyfish
with a negative refractive index", then he was on a
plane. |
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I hope it wasn't one of those new ones built using the new
pop rivet blind drill. Those things are still experimental,
you know. |
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Everything about our intercalary sibling is
experimental. |
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But enough of this. Back to the topic. |
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Yes, on with the spooky story! I _still_ want to know how it
ends... |
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//Yes, on with the spooky story! I _still_ want to
know how it ends...//
[marked-for-tagline] |
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