roy@phri.UUCP (Roy Smith) (12/14/86)
___ ______________
male thread < > ^
\------> < > | Socket for attachment screw,
< > | typical RS-232 connector
| | |
___| |___ _____ | Note: all dimensions approximate
| | ^ | not to scale
| ___ | | | typical material: brass
hex shaped | < > | 3/16 3/8
exterior --> | < ^ > | | |
|__< | >__| __v______v_
/
female thread---/
You've all seen the little gizmo described above. Most of the
RS-232 connectors on terminals, computers, and modems have one of them on
each side. Weighs about a gram. These are where you are supposed to screw
in the little screws that hold the cable from falling out. The problem
comes when you try to take the cable off a few months (or years) later.
You take a little screw driver and turn the screw in the cable
connector. To your horror, you find that the screw isn't unscrewing from
the threaded hole in the above described socket, but the whole socket is
turning! Why should this happen? Because, the socket is simply held in by
a nut and (sometimes) a lock-washer on the male end -- it's a toss-up which
threaded joint will go first (and don't give me any lip about tightening
the outside screws too tight!).
Sometimes, the socket comes out and you can just screw it back in;
not so terrible, but rather a pain in the ass. Worse is when the little
nut on the back falls off and drops down inside the piece of equipment --
now you've got this bit of metal rattling around inside your computer (or
terminal, or whatever) wreaking havoc -- a fried CPU board isn't worth
saving a few cents on a connector!
What's the solution? The short-term solution is every time I have
a piece of equipment open for whatever reason, I zap those nuts with a blob
of epoxy. The real solution is for the people who make these things to
come up with a better way of attaching the sockets. Remember a couple of
weeks ago I was singing the praises of the lowley ADM-3? Guess what?
Along with everything else the ADM-3 had going for it, it had screw sockets
that didn't fall off -- they were molded into the plastic connector shell.
Why can't other manufacturers do something like that? A keyed shaft, or a
bit of factory-applied potting compound would probably work just as well.
People I've seen do it right: Lear Siegler, Hewlett-Packard (not
surprising; I disagree with a lot of what HP does with computers, but they
sure do know how to build things), U.S. Robotics, Graph-On.
People I've seen do it wrong: Digital, Emulex, Able, C. Itoh (they
get the special prize for shipping sockets with metric threads!), Sun,
Epson, NEC, Multi-Tech, IBM (surprising; I disagree with almost everything
IBM does with computers but generally have great respect for the way they
build equipment), Volker-Craig, Texas Instruments, Advanced Electronic
Design, GTCO, Summagraphics, Apple.
--
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016
"you can't spell deoxyribonucleic without unix!"kaufman@Shasta.STANFORD.EDU (Marc Kaufman) (12/15/86)
In article <2539@phri.UUCP> roy@phri.UUCP (Roy Smith) writes: > > What's the solution? The short-term solution is every time I have >a piece of equipment open for whatever reason, I zap those nuts with a blob >of epoxy... Epoxy is a little too permanent. Try "threadlock" from Radio Shack, or Loctite 242 from your local hardware store. You stand at least SOME chance of loosening the mounting screw if you ever need to. Note that "Loctite" comes in several strengths: soft, medium, and strong. The 242 is "medium", which means that you can break it loose with a quick strong twist. If you accidently use the strong stuff, you will have to drill the screw out! I find that one can get sufficient holding power by just putting a drop on the exposed screw end, over the nut. No need to disassemble the mounting. Marc Kaufman (kaufman@shasta.stanford.edu)
thompson@dalcs.UUCP (12/17/86)
I ran into this problem too, and I thought A-ha they weren't
tight enough so I took my little socket driver and started
tighting the little..., nope, they just started breaking off
(about 1 in ten would break off). I know some people might think
that I was applying too much torque and they are right, but I
wasn't applying an unreasonable amount of torque, it's just that
the little... are made of a soft metal and break off at the
base. What is worse is that the only way to install a new one on
some boards is to drill out the thing, not an appealing approach.
--
Michael A. Thompson, Dept. Math, Stats, & C.S., Dalhousie U., Halifax, N.S.
CDN or BITNET: thompson@cs.dal.cdn CSNET: thompson%cs.dal.cdn@ubc.csnet
UUCP: ...!{garfield|seismo|utai|watmath}!dalcs!thompson
ARPA: thompson%cs.dal.cdn%ubc.csnet@CSNET-RELAY.ARPAsweet@percival.UUCP (Dan Sweet) (12/21/86)
In article <2256@dalcs.UUCP> thompson@dalcs.UUCP (Michael A. Thompson) writes: > > I ran into this problem too, and I thought A-ha they weren't > tight enough so I took my little socket driver and started > tighting the little..., nope, they just started breaking off > (about 1 in ten would break off). >-- >Michael A. Thompson, Dept. Math, Stats, & C.S., Dalhousie U., Halifax, N.S. I too had have run in to this problem, and the original one also. At the place I used to work, this problem was brought to the attention of the QC guys, I remember them talking about dumping all the old stock and specifying 'stainless steel' parts. (the vender was AMP) I do not know if they are avail, but might be worth looking in to. -- Dan Sweet ...!{ucbvax|ihnp4|seismo}!tektronix!reed!percival!sweet "Wasn't made for a human head Sarge." -Joey