PSN-L Email List Message

Subject: A "new" seismo base plate adjustment screw/s approach
From: "Meredith Lamb" meredithlamb@.............
Date: Sat, 6 Dec 2003 21:53:51 -0700


Hi all,

Have tried researching this on the PSN web site search function, but I see no reference. 
It maybe nothing new...(?)...but it sure works great!  Best of all, there is little to no adjustment
screw wobble, with quite solid firm movement.....and no base plate bolt threading (tapping)
to be done.  The normal "fitting" of the nuts to the bolts, alone by themselves is quite loose
and non-exact....but not in this application.

Basically this approach uses a standard bolt and three nuts, but, the seismo base has
only some predetermined chamfer widening of the bolt hole/s that is larger than the bolt
(adjustment screw) diameter, but only wide enough to make contact with the chamfer on
the nuts.

The nuts themselves have 6 planes (hexagonal outer shape), and some chamfering on
the outside top/bottom outside edges.  Non-chamfered nuts are useless.

One nut is above the other two; this is a locking nut only....which may or maynot be
absolutely necessary depending on how much tension the other two nuts are adjusted too.

A crude guide to trying/using this; could be the "base material" I used.  It was actually
a hardened tool steel machinist "parallel", that had two holes through the item.  The actual
hole/s were .5" in diameter but the chamfer was wider and made full contact with the nuts
chamfer (.575").  The actual bolt thread diameter was .311".  Here, the hole drilling and 
chamfer was done with a likely professional grade machine somewhere of course, but it
was likely done straight into the item without a lateral tilt offset.  If your hole and chamfer is
done by hand, the bolt may not be exactly standing upright 180 degrees to the "base plate"
material when installed.   Visually for this "model", I couldn't see any bolt tilt.

One nut is threaded on the bolt, then passed through the base material, and the other
nut is threaded on lightly finger tightened to where....the bolt can be turned (adjusted) but the
nuts don't.   With the two nuts on the bolt thread, increased turning of "a" nut, narrows
the space for the inside bolt thread, and lessens the "normal" bolt freedom to wobble.
Increased finger tightening of "a" nut makes this "bolt wobble" almost nil, and of course
makes it harder to turn the bolt (adjustment screw), but the firmness of the approach
seems to enhance the mechanical stability quite noteably.  One might call this a 
holding/tension/friction adjustment nut.  A wrench isn't needed of course for this or
the locking nut.

One may have a tough time trying to use non-chamfered holes for this approach;
most of my attempts failed with various material.  Various large drills (movement
limited) could be used for creating a chamfer; but their is other tools for this also.

One "could" epoxy the nut/s.  Epoxy one or both after adjusting the nut/s to  your
satisfaction.  Its possible the top nut "could" remain free of any cement, to adjust 
the fitting tension on the nut to their satisfaction, whenever they wish  

For smooth bolt thread movement action,  I'd suggest that the bolt/s be re-die-ed to 
eliminate burrs, or clogging matterial that might be in the threads.  I'd look for a 
straight bolt thread; theres no use buying a bent bolt.

One might also consider that in the base plate hole and between the nuts is a air
space that might serve as a "lubricant reservoir", for any of a variety of such lubricants
or types for various material.   A thicker variety of non-liquifying grease might be a good 
bet (auto grease) for the iron/steel bolts/nuts functioning over time, as well as anti-rust
prevention.

One might try this out on scrap material first before plunging into using it on the planned
for base plate installation.  One doesn't need expensive adjustment bolts/nuts with this
route.

Merry Christmas and happy new year everyone!





Hi all,
 
Have tried researching this on the PSN web site search function, but I see no reference. 
It maybe nothing new...(?)...but it sure works great!  Best of all, there is little to no adjustment
screw wobble, with quite solid firm movement.....and no base plate bolt threading (tapping)
to be done.  The normal "fitting" of the nuts to the bolts, alone by themselves is quite loose
and non-exact....but not in this application.
 
Basically this approach uses a standard bolt and three nuts, but, the seismo base has
only some predetermined chamfer widening of the bolt hole/s that is larger than the bolt
(adjustment screw) diameter, but only wide enough to make contact with the chamfer on
the nuts.
 
The nuts themselves have 6 planes (hexagonal outer shape), and some chamfering on
the outside top/bottom outside edges.  Non-chamfered nuts are useless.
 
One nut is above the other two; this is a locking nut only....which may or maynot be
absolutely necessary depending on how much tension the other two nuts are adjusted too.
 
A crude guide to trying/using this; could be the "base material" I used.  It was actually
a hardened tool steel machinist "parallel", that had two holes through the item.  The actual
hole/s were .5" in diameter but the chamfer was wider and made full contact with the nuts
chamfer (.575").  The actual bolt thread diameter was .311".  Here, the hole drilling and
chamfer was done with a likely professional grade machine somewhere of course, but it
was likely done straight into the item without a lateral tilt offset.  If your hole and chamfer is
done by hand, the bolt may not be exactly standing upright 180 degrees to the "base plate"
material when installed.   Visually for this "model", I couldn't see any bolt tilt.
 
One nut is threaded on the bolt, then passed through the base material, and the other
nut is threaded on lightly finger tightened to where....the bolt can be turned (adjusted) but the
nuts don't.   With the two nuts on the bolt thread, increased turning of "a" nut, narrows
the space for the inside bolt thread, and lessens the "normal" bolt freedom to wobble.
Increased finger tightening of "a" nut makes this "bolt wobble" almost nil, and of course
makes it harder to turn the bolt (adjustment screw), but the firmness of the approach
seems to enhance the mechanical stability quite noteably.  One might call this a
holding/tension/friction adjustment nut.  A wrench isn't needed of course for this or
the locking nut.
 
One may have a tough time trying to use non-chamfered holes for this approach;
most of my attempts failed with various material.  Various large drills (movement
limited) could be used for creating a chamfer; but their is other tools for this also.
 
One "could" epoxy the nut/s.  Epoxy one or both after adjusting the nut/s to  your
satisfaction.  Its possible the top nut "could" remain free of any cement, to adjust
the fitting tension on the nut to their satisfaction, whenever they wish 
 
For smooth bolt thread movement action,  I'd suggest that the bolt/s be re-die-ed to
eliminate burrs, or clogging matterial that might be in the threads.  I'd look for a
straight bolt thread; theres no use buying a bent bolt.
 
One might also consider that in the base plate hole and between the nuts is a air
space that might serve as a "lubricant reservoir", for any of a variety of such lubricants
or types for various material.   A thicker variety of non-liquifying grease might be a good
bet (auto grease) for the iron/steel bolts/nuts functioning over time, as well as anti-rust
prevention.
 
One might try this out on scrap material first before plunging into using it on the planned
for base plate installation.  One doesn't need expensive adjustment bolts/nuts with this
route.
 
Merry Christmas and happy new year everyone!
 
Take care, Meredith Lamb
 
 

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