[AT] OT: Cast iron work on a replica cannon

[Stephen Offiler]

Larry:  yes, with metric threads, you find the tap drill simply by
subtracting the pitch from the major diameter.  M15 x 1.0 gives a 14mm tap
drill.  Using this formula, you always end up with 77% thread engagement
for any thread, any pitch.  I'm not quite following your comment about the
reduction you use.

SO


On Sat, May 4, 2019 at 12:37 PM Rena Glover Goss <rlgoss at twc.com> wrote:

> THAT'S NO FAIR, SPENCER.  You were not supposed to figure out how simple
> those relationships are in the metric system when compared to any other
> system of threading.  I used a reduction by 1.5 millimeters so the thread
> engagement came closer to 75%, as is used in the SAE system.  There are no
> charts for pilot drills in the metric system--they simply aren't needed.
>
> Larry
> ---- Spencer Yost <spencer at rdfarms.com> wrote:
> > I’ve been giving this some more thought, and I am actually now a little
> more serious about metric if you can tolerate the idea of a metric bolt on
> a canon.. All you need are:
>
> 15 mm x 1 threads per millimeter tap.
> 14 mm drill for initial boring prior to tapping.
> A 15 mm x 1 threads per millimeter bolt at the length you need.
>
> No special tooling, no  excessive drilling diameters, etc.  A single
> thread per mm is a course pitch so it meets that requirement.  This is all
> fairly cheap, straightforward, available from major Internet retailers and
> probably your local fastener store if you have such a beast. I am lucky - I
> have three.
>
>
> Anyway you go, best of luck.
>
> Spencer Yost
>
> > On May 4, 2019, at 9:58 AM, James Peck <jamesgpeck at hotmail.com> wrote:
> >
> > About 10 years ago I was on a flight to Kansas. I can't quite remember
> the sequence of events. I heard large men speaking a language I do not
> remember hearing before as I got on the flight. One ended up seated next to
> me. Turned out they were from Dronningsborg and were going to Agco in
> Hesston for a project meeting.
> >
> > I asked what they were doing about metric fasteners. The Dane said that
> they had been all metric until Agco purchased them. They had been switched
> to mixed metric and SAE.
> >
> > It may be irrelevant. Agco shut down Dronningsborg and bought into
> Laverda. Are the combines made for Agco by Laverda all metric? Why would
> they not be?
> >
> > https://en.wikipedia.org/wiki/Randers
> >
> > [Al Jones] Metric is the work of the devil...…..
> >
> > Helicoils are wonderful.  Very easy to do and they WORK!
> >
> > My white demonstrator Super A that I have been tinkering off and on
> forever had four badly stripped holes in the torque tube.  Somebody had
> tapped the 5/8" holes out about 7/8 or so and it was BAD.  There wasn't any
> threaded inserts that I could find that would be direct replacements.  A
> machine shop friend of mine was nice enough to make a set of inserts, kind
> of like the KeenSerts, and install in the torque tube.  Once it's painted I
> don't think you'll be able to tell that anything ever happened to it!
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