[modeleng] Re: Pistons was 3½ vs 5, Sweet Pea

Harry, down at the County Jailhouse Maintenance Dept.,
we called them "Security Screwdrivers"--Spanners to
our British brethern.

Al Messer

--- Harry Wade <hww@xxxxxxxx> wrote:

> At 09:27 PM 9/26/05 +0100, you wrote:
> >Works on the 12" to the ft scale ok John, why not
> in 5" - Dave
> 
>        I have never known of a single instance where
> a threaded piston
> connection (meaning for anything other than
> retaining nut), was used in
> full size.  Certainly there may very well have been,
> but it would have been
> the extreme exception rather than the rule.
>        IF you intend to use a fully threaded
> connection, and I've done so
> myself (but won't again), the thing to do is start
> the thread in the lathe
> (between centers, in collet, or indicated in a
> 4-jaw) with a single point
> tool.  This assures axial alignment (&
> concentricity) of the thread form,
> and you have the option of running on a die for
> final shaping.  Then, more
> importantly, the piston should be finish turned to
> final OD on the rod
> between centers to insure concentricity between the
> rod and piston OD.  On
> my current loco project I intend to use a short
> tapered shank retained by a
> recessed nut as described next.
>        Another question . . . I cannot for the life
> of me remember the name
> of the type of nut & spanner combination where the
> nut has two holes
> drilled in the face and the spanner is adjustable
> with studs which fit into
> the holes.  Refresh my memory?
> 
> Regards,
> Harry
> 
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