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# Pop Rivet Blind Drill

Drill bit for producing holes designed to accept pop rivets
 (+6) [vote for, against]

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.

 — csea, Oct 20 2011

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]

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)
 — xaviergisz, Oct 20 2011

The problem is in using a blind rivet to attach a reasonably thin piece to a very thick or inaccessible base.
 — csea, Oct 20 2011

 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.

Alternatively, use a screw.
 — marklar, Oct 20 2011

 // normally used washerless //

 It depends on the application. Some are, some aren't.

 The requirement is to drill a T-shaped hole. Square corners on the expanded region are important to give the rivet "grip" when expanded.

 Alternatively, a hole shaped like an arrowhead and shaft would be acceptable.

 It might turn out to be a two-tool solution.

 1. Drill blind hole to required depth.

 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.

This has got to exist somewhere already ...
 — 8th of 7, Oct 20 2011

 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.

Does anybody know what I saw?
 — Alterother, Oct 20 2011

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.
 — bungston, Oct 20 2011

That's clever, but what is the 'flexible piece' made of?
 — Alterother, Oct 20 2011

Probably flexiblinium.
 — normzone, Oct 20 2011

 Easier yet:

 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.

Drill the hole, reverse direction to cut the slot, then back to normal direction to remove the bit.
 — MaxwellBuchanan, Oct 20 2011

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.
 — Ling, Oct 21 2011

 And to think all these year I've been tossing bits that did that... Oh, if only I'd saved them!

There's an already-baked non-wobbly version of that called a tapered (or 'step') bit.
 — Alterother, Oct 21 2011

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.
 — bungston, Oct 22 2011

 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.

 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.

 Either way, I suspect that a simple hole, just large enough to take the un-pulled rivet, will work well in most cases.

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.
 — MaxwellBuchanan, Oct 22 2011

[MB] but that's a molly, isn't it?
(Edit: Not quite. But it seems to be a "lag shield")
 — mouseposture, Oct 22 2011

Shucks. I was hoping this described a job opportunity for blind pop riveters.
 — Grogster, Oct 22 2011

Cheer up, Pop. That workman's comp'll come through any day now.
 — mouseposture, Oct 22 2011

Could a 'butterfly'-style drywall anchor be adapted to this application?
 — Alterother, Oct 22 2011

Or a blind drill team sychronised to pop music.
What?... that would be slightly riveting.
 — 2 fries shy of a happy meal, Oct 22 2011

 //Could a 'butterfly'-style drywall anchor be adapted to this application?//

Yes, but you'd still need the blind drill to make the special hole required.
 — csea, Oct 22 2011

 //[MB] but that's a molly, isn't it? (Edit: Not quite. But it seems to be a "lag shield")//

 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.

 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).

 This is so.

(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.)
 — MaxwellBuchanan, Oct 22 2011

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.
 — Ling, Oct 23 2011

I shall have to ask him. However, our intercalary twin is by now about half way to an unspecified Azore.
 — MaxwellBuchanan, Oct 23 2011

I have no idea. He said something about "jellyfish with a negative refractive index", then he was on a plane.
 — MaxwellBuchanan, Oct 23 2011

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.
 — Alterother, Oct 23 2011

 Everything about our intercalary sibling is experimental.

But enough of this. Back to the topic.
 — MaxwellBuchanan, Oct 23 2011

Yes, on with the spooky story! I _still_ want to know how it ends...
 — Alterother, Oct 23 2011

//Yes, on with the spooky story! I _still_ want to know how it ends...// [marked-for-tagline]
 — csea, Oct 22 2013

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