[TheForge] Re: Fly press question

[Dave Smucker]

The current imports from India, have compound screw with at least three or 
four leads to the screw.  This means they have a very fast advance.  The 
design shown in Mike Spencer's site uses a special screw design to do a 
similar fast advance but then a very slow advance for max loading.  A neat 
design Mike.  In the India fly presses much of the force comes from the 
stopping of the flywheel effect.

Look at the screw and see if the is more than one lead.  In other words does 
more than one thread start at the end of the screw.  2 leads will mean twice 
the advance per rev. 3 leads 3 times, 4 leads 4 times.  I have not seen more 
than 4.  You can't just count the threads per inch, you have to also look 
for more than one lead.  (Not saying that Jim doesn't know this, but many 
folks miss this when looking at or measuring the tpi.)

All fly press are good.  Slow feed better for cold work such as cold die 
work or coining, fast for forging.  But both can work outside of their 
intended area.

Dave Smucker




>From: mspencer at tallships.ca (Mike Spencer)
>Reply-To: mspencer at tallships.ca,Sponsored by ABANA 
><theforge at mailman.qth.net>
>To: theforge at mailman.qth.net
>Subject: [TheForge] Re: Fly press question
>Date: Mon, 4 Jul 2005 13:15:03 -0300
>
>Chuck Robinson quoth:
>
> > There supposedly are presses with compound screw pitches and a
> > pressure activated compound nut that changes from coarse to fine
> > pitch when resistance is met.
>
>Thanks for the enlightenment, Chuck.  I thought they were *all* like
>that.  That feature is the one thing that makes a flypress a Very
>Clever Device instead of just another useful whatsit. FWIW, see:
>
>     http://home.tallships.ca/mspencer/nut.html
>
>The screw shown there was in a disused architectural ceramics factory
>in England and had been used to ram slighty damp clay powder into
>a mould.  Apparently this is a much faster and more controlable
>process that either slip casting or working with wet clay.  I've heard
>the the old TD clay pipes were made this way, too.
>
>I would pay good money to get a press with the dual pitch.  A single
>pitch press would have to be a bargain.
>
>- Mike
>
>--
>Michael Spencer                  Nova Scotia, Canada       .~.
>                                                            /V\
>mspencer at tallships.ca                                     /( )\
>http://home.tallships.ca/mspencer/                        ^^-^^
>
>--
>
>
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