PSN-L Email List Message

Subject: Re: A "new" seismo base plate adjustment screw/s approach
From: "Meredith Lamb" meredithlamb@.............
Date: Mon, 8 Dec 2003 11:39:07 -0700

Hi John and all,

Perhaps the best line of use for this, could be for either very thin
thickness base materials
(~1/8" or so), or those occasional items found with holes already present,
but which don't
offer a ready immediate solution for the standard threading approach.  It
could also work
where threaded holes are present, but the necessary size bolts are absent. 

I think most American made threaded nuts have some amount of a 30 degree
moreso on one side than the other side.  Even the little 6/32 size seems
too, which is
encouraging for this application.  Of course, its the larger sizes that
offer the greatest
amount of chamfer area, that will make contact with the chamfered walls of
the base plate.

I checked my table top model for this aspect of the possibility of the
epoxy (or whatever)
seeping through.  By holding the model up between my eyes and a light
source, while
cupping the one side, on two of them there was no light (a solid contact);
but the third
one did show some small areas of light.  That of course, would mean either
that the base plate
chamfer was insufficient and/or the nut/s themselves were too blame; so
either a better/deeper
chamfer can be done and other nuts substituted and observed for light
leaks.   As things
can go, I'd say that there will always be the possibility that it when a
glue/adhesive is 
applied, there is a risk of the material getting on the bolt threads.

Its necessary to make the base plate chamfer/s slightly wider than the nut
thats used, so full
contact is made.

As to the subject of "epoxy"; as a adhesive too me and my experience, its
kind of a failure
prone material to use.   It might even be smarter to use a rubber like
material like clear silicon
caulking as it can be removed should the need arise; and/or a adjustment on
the top side
may seem to be indicated in the future after installation and use for some

One aspect of this approach, is that one can use the universal metric or
American or any
other regional standard bolt/nut sizes; as long as as they have the right
base plate hole,
or hole making drill and or chamfer/bevel tools.    

Interesting thought John, on the lock washer idea.  I'd think one would
have to "crunch"
the lock washing into the bevel shaped depression on the base plate to have
it work; and,
it maybe only applicable to one side of the plate.  They usually "bite
into" most materials;
but not usually the nuts.  Theirs afew kinds of lock washers around; one
might have to
experiment to see what works.  

Most amateurs will likely use aluminum as the base plate....its possible to
even torque
a nut in enough to where parts of the nut/s dig slightly into the aluminum
on one side of
the plate.  When torqueing, I'd temporarily use a flat washer on one side
(nut), so that, that
other side does dig will likely need the one clean side for
adjustments movement.
Its also possible that this action might upset the angle of the bolt to the
base however.
Personally, I think I'd avoid this approach.

Take care, Meredith

> [Original Message]
> From: John or Jan Lahr 
> To: 
> Date: 12/7/2003 8:31:02 PM
> Subject: Re: A "new" seismo base plate adjustment screw/s approach
> Hi Meredith,
> Sounds like a good design!   I had to look up the word "chamfer"
> "To cut off the edge or corner of; to bevel."  I guess you would
> chamfer both sides of the hole in the base plate.
** Yes, there would be chamfer/bevel on each side of the base plate hole/s.

> I would seem that one would have to epoxy the lower nut at least
> to prevent if from turning, but maybe a lock washer above and below
> would prevent that and avoid the possibility of getting epoxy in the
> wrong place.
> Cheers,
> John


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