[TheForge] Nuts

Thu Dec 11 10:57:01 2003

Dan,  It depends on how "fast" you run the screw and how much torque you put
into it. At least that is the way it is on rolling mills.  Many rolling
mills have ACME treads for the main power screw downs.  (Today most new one
are hydraulic.)  On hot reversing mills you have a high speed screw and not
real high horsepower because the screw runs without metal in the mill.  It
is high speed because you have to make large changes in the gap of the
mill -- say starting with ingot as thick as 24 inches and running on down to
1/8 of an inch in some cases.  These screws are very easy to jam -- if you
run the mill closed at high speed you can put enough load on the mill that
you can't back the screw off.  The reason is the inertia in the screw
turning at high speed.  I have seen jams so bad that we had to grind a flat
on the roll face by hand and then turn the roll into the mill to relieve the
pressure.  This is a very expense screw up (screw down).   I have never seen
a jam in an ACME screw on a cold mill -- because they are slow and designed
to operate under load -- i.e. lots of torque.  The biggest ACME screw I
worked with was 36 inch dia for the plate mill at Davenport, IA.  It unlike
those I note above was designed to run under load to roll tapered plate for
aircraft wings.  It could produce 10,000,000 pounds of load.

Now for your small screws -- many C - Clamps and Bar - Clamps have ACME
threads. I never seen one that you couldn't open if you got a long enough
cheater.  Not sure why a vise should be any different.  If you had a way to
put more load on them than via the tighting torque it may be a problem.  For
example -- close a vise on a wedge and then drive the wedge deeper into the
vise.  Only a blacksmith would do something like that :-)

Dave Smucker
----- Original Message ----- 
From: "Dan Tull" <[email protected]>
To: <[email protected]>
Sent: Thursday, December 11, 2003 10:02 AM
Subject: Re: [TheForge] Nuts

> Somewhere I heard that Acme threads seize up to make breaking loose a vise
> difficult.
> i.e.  vise was not a good application. Anyone have experience w/  that?
>
> dan tull
> georgia
> abba, afc, S.C. psba, obg,sofa
> ----- Original Message ----- 
> From: "Michael Horgan" <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, December 10, 2003 11:12 PM
> Subject: Re: [TheForge] Nuts
>
>
> > Ought to make nice vice screws, Dave.
>
>
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