Re: Deane Kidd and the Metric System

Fabio Trevisan


I think what Ian Newman meant is that you can easily do that conversion by
heart, without resorting to a calculator or a piece of paper to make the
full division or multiplication operation.
It's a no-brainer to repeatedly double the quotient and the divisor until
the divisor reaches 256, and just take note of what the quotient became to
get the result directly in 10ths of mm. With an error of just 0.78%!

I think it goes particularly intuitive to the ones of us who dealt more
with binary logic who can tell by heart most of the smaller powers of 2 and
the relation between all of them.

Rgrds from Brazil,


2017-12-15 11:28 GMT-02:00 Eric J [TekScopes] <>:

Same. I was a machinist, toolmaker and welder for 20 years until I injured
my back. We always used 25.4 for conversion from inch to metric and vice
versa, it is correct and gives the exact conversion.
Sent from my Samsung Galaxy S8.
-------- Original message --------From: "Barry
[TekScopes]" <> Date: 12/14/17 7:48 PM
(GMT-06:00) To: Subject: Re: [TekScopes] Deane
Kidd and the Metric System

I worked in a metric shop for 10 years. I pretty much always used 25.4 as
the conversion factor. 0.03937 is a rounded recriprocal of 25.4 which is
technically the correct conversion factor between inches and millimeters
(and easier for me to remember).


Barry - N4BUQ

----- Original Message -----

From: "Tom Jobe [TekScopes]" <>

Sent: Thursday, December 14, 2017 6:36:53 PM
Subject: Re: [TekScopes] Deane Kidd and the Metric System
That is a very neat trick... but consider this simple plan:
For the fractional part of the dimension, divide the bottom number into
the top number to get its decimal equivalent.
Example (7/16" = 7 divided by 16 gives you 0.4375 inches)
If there are whole inches involved in the measurement then it becomes
1.4375, 2.4375 etc.
Divide the decimal inch number by .03937 and you have your millimeter
Example ( our 7/16" is 0.4375 decimal inches, we divide it by .03937 and
we have our answer of 11.11125 mm.
Memorizing the number .03937 solves the whole problem going either way,
to or from inches and millimeters.
Let's have an example of going from millimeters to inches:
If you multiply 100mm by .03937 you will get it's equivalent in inches,
100 x .03937 = 3.937 inches.
The number .03937 is simply how many inches are in one millimeter.
This .03937 method was the common way that millimeters and inches were
dealt with in shops I worked at in the US.
tom jobe...
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