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

Sat May 4 17:58:07 PDT 2019

It has been too long since I did this, Stephen.  I used to teach this material to engineering and engineering technology students, but have been retired for 18 years, and gave all my metric taps, dies, drills, and wrenches to one of my grandsons when I downsized.  

I used to get criticized by faculty colleagues because I taught my drafting and graphics courses only in metric units.  I told them the students really didn't know how to use any of the four systems of measurement, and that they would develop a decent sense of at least one of them if they didn't have to be confused by dealing with the others.  I don't think my colleagues necessarily "bought" my argument, but I did find that things were much simpler when students only had to deal with a single measurement device.  I think I still have metric, architectural, mechanical engineering, and civil engineering scales laying around--but not nearly as many of them as I used to.

So tell me-- How long is a surveyor's chain, and what are the units in it?  This is not an esoteric question.  Our family is currently dealing with a real estate transfer that dates to the original survey for the Wabash-Erie canal.  The concepts of Range and Township were still reasonably new at that time, and the units of measure corresponded to the most current technology.

Larry
---- Stephen Offiler <soffiler at gmail.com> wrote: 
> 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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