A topic for Glenn or Harold re: metrics

[Mr Ron]

I'm asking this question of you because you are retired machinists and probably worked all your lives with the Imperial measurement system. There are many forums where the pros and cons of the metric vs the Imperial systems are discussed. None have ever concluded conclusively which system better. So I ask you and any other reader to respond to this universal debate coming from a machinist's perspective alone. Many arguments have been presented stating the metric system is easier to learn. (I never found it difficult to learn the Imperial system) Like a lot of others, we can work in both systems when necessary, but we all have a preference. My work in the shipbuilding industry was in the Imperial system, but metrics were also used in some jobs involving foreign vessels, but at home in my shop, I'm perfectly comfortable with feet and inches. I would suspect most machinists over the age of 50 have been brought up in the Imperial system.

[GlennW]

Hello Ron,

I'm not a Machinist, and unfortunately not retired either! (56)

I was brought up on the Imperial system and have had no need to do any work with the Metric system so far, other than tinker with my motorcycle occasionally.

The Metric system seems like a foreign language to me, but mainly because I have never really used it and have never tried to "think" in Metric. I do have a basic understanding of it, but it's just not natural to me. Imperial works fine for me!

[DeMaxx]

Hello Ron,
I am a retired machinist and I worked all my life with the Imperial system. I understand Metrics fairly well, it just doesn't come naturally to me. My machines and measuring tools speak Metric just by the touch of a button but I still think in the Imperial system. Just by force of habit I suppose.

Tom

[Rich_Carlstedt]

I have spent my career working in both.
Because of my metric knowledge, I was hired by American companies to help install European equipment, and I translate measurments to millwrights in my head most all the time. I feel I am unbiased about the subject matter.

First, no system is better than the other !
One may be "eaiser" than the other in certain arears, but better is a misnomer. ( IMHO)
Most folks have a mental blockage when it comes to metrics, too bad.
When I am threading , I may use any number of threads, and even use imperial and metric on the same project.
" Horrors" you say...well, Each has a certain size advantage, but since we are machinists, let me ask you a question .
A. Have you ever tapped a 8-32 hole
B. Have you ever tapped a 5/32-32 hole
C. Have you ever tapped a 4-.75 mm hole

All three are about the same size, yet different.
For Imperial decimal backers, I bet you don't know the major OD of "A"..You need to look it up ( .164 by the way).
For Imperial fraction backers, I bet you don't use a ruler when working with threads, you grab a mike and look at the table, or calculator ! Fractions are difficult !
For Metric backers, its not easy to use a "75" % number when working in millimeters which has a base of 1000. You have a fraction !
Lets assume no thread gauge is available
Say I hand you "A" and ask what the read count is ? You would place a inch scale next to it and count the threads in that inch.
Say I hand you "C" and ask the thread size? you would have to have to count threads, and then measure, and then divide ( is it .7 or .75 ? for example)

So what is better ....or should I say where?
Architectural, uses Feet, inches, fractions. That is a real bummer as it has 3 different relationships in one.
Metrics are far better for long measurement in such cases, as everything is based on the Meter

Machine work always carries the addage that metric is better, because for tapping , you deduct the pitch from the OD for the tap drill size. Makes sense, so lets look at C above, it needs a 3.25 drill . but wait, the drill case has drills by .1mm divisions ( ie 3.2, 3.3, 3.4) so that does not work. Now you have to convert dimensions or make substitutions.
For machine work with small dimensions, I give the edge to Decimal Inches.

For ball bearings, the edge is with metric, because they invented BB and most sizes are therefore metric
For Roller bearings the edge is imperial , again because they invented them and most sizes are imperial.
For tapered pipe sizes, again, Imperial has the edge.

So whats better ?
it all personal, but I like all of them !
Rich

PS My pet peeve.
Schools teach "centimeters" yet in all my dealings with Europeans and Japanese engineers, they never used Centimeters !
Schools teach metrics incorrectly and is one reason for the adversion to this wonderful form of measurement

[Mr Ron]

I have spent my career working in both.
Because of my metric knowledge, I was hired by American companies to help install European equipment, and I translate measurments to millwrights in my head most all the time. I feel I am unbiased about the subject matter.

First, no system is better than the other !
One may be "eaiser" than the other in certain arears, but better is a misnomer. ( IMHO)
Most folks have a mental blockage when it comes to metrics, too bad.
When I am threading , I may use any number of threads, and even use imperial and metric on the same project.
" Horrors" you say...well, Each has a certain size advantage, but since we are machinists, let me ask you a question .
A. Have you ever tapped a 8-32 hole
B. Have you ever tapped a 5/32-32 hole
C. Have you ever tapped a 4-.75 mm hole

All three are about the same size, yet different.
For Imperial decimal backers, I bet you don't know the major OD of "A"..You need to look it up ( .164 by the way).
For Imperial fraction backers, I bet you don't use a ruler when working with threads, you grab a mike and look at the table, or calculator ! Fractions are difficult !
For Metric backers, its not easy to use a "75" % number when working in millimeters which has a base of 1000. You have a fraction !
Lets assume no thread gauge is available
Say I hand you "A" and ask what the read count is ? You would place a inch scale next to it and count the threads in that inch.
Say I hand you "C" and ask the thread size? you would have to have to count threads, and then measure, and then divide ( is it .7 or .75 ? for example)

So what is better ....or should I say where?
Architectural, uses Feet, inches, fractions. That is a real bummer as it has 3 different relationships in one.
Metrics are far better for long measurement in such cases, as everything is based on the Meter

Machine work always carries the addage that metric is better, because for tapping , you deduct the pitch from the OD for the tap drill size. Makes sense, so lets look at C above, it needs a 3.25 drill . but wait, the drill case has drills by .1mm divisions ( ie 3.2, 3.3, 3.4) so that does not work. Now you have to convert dimensions or make substitutions.
For machine work with small dimensions, I give the edge to Decimal Inches.

For ball bearings, the edge is with metric, because they invented BB and most sizes are therefore metric
For Roller bearings the edge is imperial , again because they invented them and most sizes are imperial.
For tapered pipe sizes, again, Imperial has the edge.

So whats better ?
it all personal, but I like all of them !
Rich

PS My pet peeve.
Schools teach "centimeters" yet in all my dealings with Europeans and Japanese engineers, they never used Centimeters !
Schools teach metrics incorrectly and is one reason for the adversion to this wonderful form of measurement

In my case, I have the dimensions, tap drill sizes, etc in my head because they are common sizes I use all the time. The Starrett wall chart in my shop reminds me for thread sizes and equivalents not commonly used. My main reason for using Imperial aside from that was what I learned, is the investment I have in precision tools.

[Mr Ron]

Hello Ron,

I'm not a Machinist, and unfortunately not retired either! (56)

I was brought up on the Imperial system and have had no need to do any work with the Metric system so far, other than tinker with my motorcycle occasionally.

The Metric system seems like a foreign language to me, but mainly because I have never really used it and have never tried to "think" in Metric. I do have a basic understanding of it, but it's just not natural to me. Imperial works fine for me!

Sorry Glenn. I didn't mean to insult you.

[revrnd]

Growing up in Canada, I was about halfway thru grade school when the big switch to metric was made (Gov't decree).

I worked @ GM from '81 to '08. As we went along more & more of the vehicles became metric. That being said if we were working on "homegrown" tooling for ourselves we'd design it using Imperial dimesioning w/ Metric fasteners. Heck mat'l is still Imperial sized. I've never heard of steel shops stocking 6 mm x 100 mm cold rolled.

If I'm designing stuff in my shop, I use Imperial.

It strikes me funny that you chaps are referring to the "old" measurement system as Imperial. I see most US hand tool companies refer to it as SAE when describing Imperial wrenches or sockets. Is this a marketing thing or has the SAE taken "ownership" of the Imperial system?

[lakeside53]

I flip back and forth with no real issues.. Neither is better than the other. I've spent half my life in "metric countries", but even those are not totally metric.

In the USA metric is everywhere and a fact of life. It's easy to to ignore even if you deal with the very common metric bearings and shafts fits, but you have to convert them to "funny looking" imperial measures

I just punch a buttom on my cnc mill and it flips from one to the other. My lathe has dual dials. My mics are all imperial, so I have to convert, but my machinist calc does that with one button. Often I'll have a metric sized object mounted inside of an imperial device. I put both measures on the drawing.

[Lew Hartswick]

It strikes me funny that you chaps are referring to the "old" measurement system as Imperial. I see most US hand tool companies refer to it as SAE when describing Imperial wrenches or sockets. Is this a marketing thing or has the SAE taken "ownership" of the Imperial system?

My take is that since the source of "Imperial" has abandoned the "system" it must have a new name.
So what is wrong with SAE. adopting it. ?
...lew...

[mcostello]

At one of my favorite nut and bolt, and fastener stores there is a desk top size poster of bolts, giving examples of head designs, preferred threads and other related information. While waiting for an order to get filled I looked the chart over and noticed one Metric size specification that said " no Drillbits in this size comonally available". Someone sure thought that size through. Have yet to see that with Imperial.

[ken572]

Mr.Ron,

I think we are most comfortable with the things and
system's we grew up with and learned how to use.

Note: Most all System's, Method's, etc., are all needed
from time to time, and there are really none better then
another.

We all just need to learn to use them when there is a
need for them. It makes us smarter

These are some helpful links that help me when needed.
http://www.gewinde-normen.de/en/index.html

http://www.baconsdozen.co.uk/tools/conv ... charts.htm

http://www.engineersedge.com/hardware/DIN-ISO-228.htm

Ken.

[Harold_V]

The problem I have with metric is my inability to relate to size. If a metric dimension is given, I immediately convert to Imperial, where my brain has a sense of size. That's not to say one system is better than the other, as I don't believe that to be the case.

Converting from imperial to metric has its problems. Take, for example, the way those of us who are familiar with imperial threads, measure thread pitch. Our system designates threads per inch, while metric designates pitch distance of one turn. Both work just fine, but you have to keep them straight in your head.

I was taught the imperial system, from a very young age. I was reading a micrometer at age 14. I think thousandths, even when other folks talk fractions. No big deal---it's what you get used to.

Given a choice, there would be no metric in my world.

Why?

Because I'm old, and because I understand the imperial system about as well as it can be understood, and I'm very comfortable with its use. But, the best reason I can offer is, I don't like change. Period! Don't fix the damned thing if it isn't broken, and, to my knowledge, it isn't.

Harold