On 2011-10-06, DougC wrote:
Is there such a thing? The usual places show nothing of the kind.
Countersunk-head screws fit flush with the surface of course, but
another aspect of them is that they stay centered in the holes. Is there
a nut with a conical contact area to fit similarly?
Yes. One place to find them is in the old metal-flanged NAB
10-1/2" audio tape reels. They have a cylindrical projection below
the head. These are 6-32 screws and nuts.
Now -- normal ones are called "sex nuts" or sometimes "sex
bolts", and you can see a drawing of one at the bottom of this web page:
http://www.boltdepot.com/fastener-information/Measuring/Measure-Length.aspx
Do a search on "sex nuts" and "sex bolts" to see if you can find
what you want.
Or -- if not -- you could get a countersunk Rivnut and use it
backwards. I can't find one on eBay at the moment, but the normal
flat-head ones look like this:
eBay auction # 120569009508
(no clue what size this one happens to be.)
Note that the part near the head is not threaded, only the bottom half
is threaded, and it normally is put into a hole then pulled so the
threaded half gets closer to the head and the walls expand to hold it in
the sheet metal. And often there is a radial projection to keep the
rivnut from rotating in the panel. There is a special tool for pulling
the rivnut to lock it in, and another special tool to cut a notch in the
hole to engage the radial projection. You want countersunk and no
radial ridge under the head. And you are using it backwards.
I know a lot of nuts have one or both sides sort of a rounded-off, but
the contact area is not nearly the entire possible.... and I know I
could trim some regular high nuts or coupling nuts off if I only needed
a few, but that would be impractical when I needed 50-100-200 or more.
Even less so when I needed smaller sizes--#8, #10....
The Rivnuts come in sizes at least from 4-40 to 3/8-"whatever
pitch" -- to lazy to see what I actually have.
O.K. Here is a supplier:
http://www.gen-aircraft-hardware.com/template.asp?pagename=rn
Note that the 4th of these is a countersunk rivnut, and maybe the next
to the last in the first photo.
Download the pdf of their Blind Rivet Nuts page (3 pages) and
you will find that they have them in 6-32, 8-32, 10-32 and 1/4-28.
And you don't really need to worry about the grip range, as you
are using them backwards. :-) (Oh yes -- you might need to make a holder
to hold them while you drive a Phillips screwdriver into the head, if
you want a Phillips head in it. If you can simply hold it in place with
your thumb while you tighten the other side, no problem.
In a perfect world there would exist 'countersunk' nylon-washer-style
locking nuts.... as long as they're not a mil-spec item where a 1/4-20#
costs a dollar each....
They would be. :-)
Good Luck,
DoN.
--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---