BH Screws

[Jerry Forwood]

Question?
Why would a kit manufacturer use a "Tamper Proof" screw on something that by definition surely be "Tampered with"?


73 de Jerry, KØEJF
E.J.(Jerry) Forwood

-- Fred Olsen <fwolsen at EXECPC.COM> wrote:
Folks, here's my two cents' worth to try to clear this up a little.  I'm
sure of it but you believe what you wish.

When specifying production hardware, or writing a parts list or bill of
material, there are certain common abbreviations used.  These can
include but are not limited to RHMS, FHMS, PHMS, and BHMS.  Those
signify 'round', 'flat', 'pan', and 'binding' head machine screw.  There
are numerous others but because they are much less common, standard
engineering practice dictates that they are normally spelled out.
'Button', truss', and 'fillister' come to mind.

This is in no way an absolute, and different houses follow widely
varying conventions, but proper practice intends to leave no doubt as to
what's called for.  These are all HEAD style callouts and have nothing
to do with DRIVE style.  One won't find all drives available on all
heads, surely, but there are many common combinations.

Specifics relating to prior questions or statements:
A binder is similar to a pan, sometimes with a slightly larger head
diameter per size, but differs in having a concentric relieved area on
the underside of the head, adjacent to the shank.  It does provide some
anti-rotation due to deformation of the head when applied within a
specific range of torque.  The higher specific pressure of the reduced
head contact surface also improves retention on some surfaces.

A button is a more rounded head.  It usually employs a socket drive such
as a hex, spline, or Torx.  It is often used in 'dress' applications,
sometimes with a special painted or plated finish.  I can't off hand
recall where Heath used any button heads, so to the best of my knowledge
in Heath-speak BH means 'binding head'.  That is not by way of
requesting an argument.  If anyone is aware of an application I'm sure
they'll be pleased to let us all know about it.

Nearly any drive style is available in a tamper-resistant version.  That
has nothing at all to do with the head style or drive style, but is a
separate issue.  Again, some styles better lend themselves to it than
others.  There is no such thing as tamper-proof, short of welding.  Any
vandal can buy any bit style.  Some styles are more highly
tamper-resistant.  Go hang around a public lavatory and check out
"toilet screws".

For a good time call ...  No, wait a minute.  For a further education in
the arcane world of fasteners a quick course can be had from the
McMaster-Carr catalog.
http://www.mcmaster.com/

Fred
--
<><
--
Outgoing checked by Norton AV

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