On Sep 26, 2014, at 8:30 AM, Chuck Ramsey  wrote:

> Galoots,
> 
> I purchased a folding rule this summer at a flea.  I pulled it out the other
day
> and started to wonder about when tape measures replaced folding rules for
> on the job site carpenters?  Do any of you still use a folding rule?  When and
for
> what?  What might be the advantages of a folding rule?
> 
I don't think I have told you guys this one before. Back in 1988 I hired on at
Ameron Pipe Company as a "Large Diameter Pipe Layout Man." Everything over 24"
in diameter is considered "large diameter," and there are special skills needed
to do this kind of layout work, the most important being trigonometry. So I took
the test and passed. The first couple of days I followed the senior layout man
around to get the feel of the place and the work. At this shop they made pipe
and fittings only up to 13 feet in diameter (it is called "156" because pipe is
always referred to in inches, never feet), because that was the largest size
that could legally be transported on California highways. Bigger pipe can be
made, but it has to be made on site. We made 21 foot diameter pipe for the
Arizona Water Project.


Laying out, cutting, and forming plate steel into large pipe fittings is most of
the work in the fittings shop, and large diameter fittings require big pieces of
plate. Plate steel is quite expensive, and mistakes are not suffered gladly. Big
reducers sometimes have to be made in 2 or more pieces and welded together,
because steel plate just doesn't come that big. The large end of a 156 reducer
will have a  circumference of more than 40 feet. Very difficult to buy a plate
that long.

So when the senior guy showed me how he laid out a large reducer, I was rather
surprised. What they did in this shop was to use the angle to calculate a
percentage of the circumference, which gave them the arc length. Then they swung
this arc with a very large trammel type device. Now they used a steel folding
rule to measure the length of the arc. The ends of the arc were then drawn back
to the center. This gave them the layout for a reducer.

To bend the rule they used large magnets on the plate and bent the rule around
these magnets. This was a really cumbersome method. It worked, but it was from
another century. I immediately offered to show him how to lay out the chord,
which would give him the intersections on both ends of the arc, and eliminate
that arc measurement altogether. He just looked at me like a bull at a bastard
calf, and informed me that they had always done it this way, and would continue
to do so. The truth was, he didn't know if he could trust the calculation of the
chord to give him an accurate arc.

A few years later I was Superintendent of the plant, but I never was able to get
anyone to believe me. They still do the same layout today. I still own two
different 12" long steel folding rules, and one in aluminum. I never use any of
them.