[TheForge] Fly Press

[theforge@mailman.qth.net]

Regarding cutting the thread on the lathe,  there are a lot of tricks to 
cutting acme threads in general and.  You leave a landing zone on the 
end of the shaft next to the chuck, that is cut down to thread depth or 
a little greater so that you have a safe place to disengage the splitnut 
and retract.   I also start cutting with a narrow v thread tool and 
clean up with an acme profile tool.   Also I have used a gooseneck tool 
that let me turn the rpm way down ad still get a decent finish.

I lucked into several 2.5" acme screws like you describe except they are 
hollow ( about 3/8" - 1/2 "wall thickness) .  They were part of the 
landing gear retraction system for an airforce bomber.  Never knew what 
I would use them for until now.....

BTW, your machine looks great, the only question I have is why you 
painted it chinese green???

Charles

Don Sinclaire wrote:

>If I use a 2-inch screw, it should really have a much coarser thread so that
>it still goes down fast enough- it should almost free-wheel down on its own
>in order to have a good "feel" and not bind when it bottoms out. I don't
>think it is possible to turn a screw like this on a lathe, since it would
>advance so fast that you would have to be careful not to run the tool into
>the chuck.  Check the other posting regarding the use of a screw from a gate
>valve.  Probably not a good choice, but I have not rulled it out yet.
>
>I would like to try a 2-inch 4TPI Acme screw, but the bolt supply shop here
>wants $105 for a 3-foot length, and the nut is $40.  And that is at
>wholesale.  If you can find those parts at the scrap yard at 15 cents a
>pound, it would be worth a try.  At worst you would have a pretty good arbor
>press.
>  
>