metric drill set explained?

[tornitore45]

Russ, then your experience with Kubota has nothing to do with metric vs imperial, is simply a case of poor manufacturing standardization and procedure. When I designed product for large quantity manufacturing we had to review DFX Designed For "whatever you like to add" in place of X: Assembly, maintenance, sourcing, testability, shippability, safety etc.
I was the only engineer that went as far as reviewing the components list, mainly resistor and capacitor and reduced the number of different Items.
For example in a resistor divider the ratio is important and resistors are specified at 1% but the absolute value can stand a wider range of choice so one of the two resistor can be chosen to match one that is used already. If I had 76 capacitor rated 50V and 3 caps rated 25V they will all be 50V the saving of handling one less item more that made up for the 1/2 cent difference.
Sloppy engineering can be found all around the globe.

[Magicniner]

That said, I'm sure living in a nominally metric country would provide a higher hit rate, but again, that doesn't speak to the superiority of the metric fastener system. As far as I think I understand, if I had a home shop there, and wanted the same "on hand" coverage I currently enjoy with my "standard" fastener bins, I would need at least 3 times the space just to cover the same basic range.

Yeah, you'd think that but it ain't so

[BadDog]

Which part? The better hit rate when buying fasteners, or that I would need 3 times the storage for a comparable "on hand" hit rate? Depending on which I'm wrong about, the pro/con could shift substantially either way.

[BadDog]

Russ, then your experience with Kubota has nothing to do with metric vs imperial, is simply a case of poor manufacturing standardization and procedure.

But my Kubota was simply a reference to my worst recent experience. The fact (or so I think it to be) remains, for each nominal metric size, of which there are more for a given domain range, and more thread pitches for each, you need a LOT more stock to cover your bases. For example with "standard" with an automotive (and general around the house etc) focus, it is mostly covered by 1/4", 5/16", and 3/8" with a few outliers like 1/2" for chassis components, various for special such as head/main bolts), and most all those are coarse thread, with a few grade differences. So it takes very little stock to cover all common bases other than length (achieved with some cutting). Try that for "metric" automobiles. There is a larger range than that in any given Japanese brand. European has their own selection from the massive metric assortment. To make that worse, in the US, a nominal domestic brand will have their own take on "standard" metric fasteners for US origin (depends on def) vehicles, plus various within any brand that may source from Japan, Korea, or Europe with their own takes on preferred fasteners. Ford always seemed to prefer odd head sizes, like 11 and 13 mm. Japanese preferred even. And the odds of encountering a same size bolt with a different pitch in the same car is much higher. But older domestic iron that predates metrification and offshoring, my collection of standard bolts would way more than cover me on just about anything that wasn't a specialty fastener. I won't even get into the bastard half breeds that started getting traction in the late 80s where it's metric in the fuel system (except these exceptions), and standard on the chassis (with these exceptions, and... Don't' even get me started on tube/hose fittings.

But back to the point. Metric proponents will inevitably beat the drum of unit conversion simplicity (both amplitude and domain), and it's a very valid drum to beat. However, they inevitably minimize/trivialize reality of the shortcomings of metric system applied in the real world (as applies to "most" of us). Sure, it's not an indictment of the metric system that the application is so fubar'd world wide, but don't try to get me to swallow that somehow everything would be better if the US would just get with the program and go metric. There are many ways that would be true, and I actually do support doing that for those very reasons; but what we would get in the end is in no way the rainbows and unicorns world promised by "the metric system", particularly in dealing with legacy systems in the US (and parts of Europe).

In context with my fasteners focus, the (my) world would it be better if we could eliminate the category of "standard fasteners" today. By definition, if I wanted to cover all automotive (and general use) bases with stock on hand, that stockpile would be smaller, because then I would only need metric. If only we had a magic wand to make it so with no legacy systems to deal with. But taken just as fasteners, with the threading issues, plus the vastly wider range of "standard" metric fasteners (sizes x pitches), if one were to be obliterated by magic wand, and that wand were in my hands, standard/customary/imperial would not be the system of fasteners that vanished...

[Mr Ron]

I have two stories about English vs metric. The first is about the conversion of a U.S. navy tanker that was cut in half and a new mid section added. The conversion was done in the U.S., but the mid section was fabricated in Taiwan and shipped here via a barge. When it got time to put the pieces together, it was discovered to much horror, that the new mid section was a full 10" out. The outside hull did line up, but the longitudinals did not. It appears Taiwan built the mid section using the metric system, converting dimensions to metric units, but rounding off. The dimensions soon started to accumulate until the outermost longitudinal was a full 10" away from it's mating longitudinal. The fix was to remove 3' from the ends of the longitudinals and add a transition piece. This happened to 4 ships during a project called AO jumbo.

The second was when I was working on a rehab on a Venezuelan navy ship. The ship being rehabed in an American shipyard was built in Italy and therefore was built in metric units. Steel plates and shapes were not available in metric units, so American units were substituted in lieu of metric. That same went for fasteners and any other item that there was not a metric part for. In general, any substitute was made using the next size larger. It all worked out well and the ship turned out better than when it was built. While all this was taking place, I(we) had to produce drawings and convert metric to English and visa-versa.To make things even more complicated, the ship's drawings were in Italian and the ship's personnel spoke Spanish. During this job, we had to hire a bunch of interpreters for the language differences and a liaison to relay communications between us and the Venezuelan navy. My wife who speaks Spanish was enlisted on occasion to help translate documents from English to Spanish. These documents were to become part of the package we supplied to them at the end of the project. BTW, she never received any payment for her work, but was in support of projects I was working on. An example was for a drydock schedule, that needed to be bi-lingual for use in Spanish speaking countries.

What does all this have to do with metric drills? Not much! To the ordinary person on the street, it can be a big concern, but to the engineer, we just crunch the numbers and make the substitutes as needed, without any fanfare.

[Magicniner]

The problems are not with measurement systems, the shortcomings lie with the users who can't cope with basic maths or make stupid assumptions. The ship example above just shows that not everyone understands Cumulative Error
I have to work with a mix of metric and imperial fasteners and I find both are fine, for the whiners I'll point out that one pitch gauge set covers all Metric threads and I need several for Imperial (Yes, that's what the Inch system is actually called Imperial )

[Harold_V]

Don't misunderstand. I can work with metric, I just prefer not to. That's true even though my lathe will readily dial metric threads. I don't find it very convenient that I can't use the half nuts, however.

My approach is dead simple. I convert any metric dimensions to (as you say) Imperial dimensions. That's how my instruments read, plus it helps me form a mental picture of real size, which doesn't happen for me with metrics.

In regards to pitch gauges, it's not clear to me why one needs more than one for Imperial sizes. I have one that covers virtually every conceivable pitch you'd encounter in life, maybe more. If one was to buy one with a half dozen leaves,it surely won't cover the full range of American Standard thread sizes, but then that's true of metric thread gauges, too.

At a technical level, there may be advantages to the metric system, but for the guy on the machine, especially when he is well in tune with the system in use (Imperial, or what ever it is), I dare say that the likes of Glenn would be just as comfortable with the system as anyone could be with metric, and he certainly wouldn't take a back seat to those who do. The system of measurement has nothing to do with one's ability to perform, nor does if affect the outcome.

Clumsy as it may seem to some folks, the system we use works, and works well. Those of us who understand the system are not the least bit inconvenienced near as I can tell. I know I'm not.

Both systems will endure, and the world will adjust accordingly. If that isn't the case, I'd like to know who's going to reimburse me for the change that some feel is mandatory.

I like Starrett tools. Send a full complement.

H

[BadDog]

The problems are not with measurement systems, the shortcomings lie with the users who can't cope with basic maths or make stupid assumptions. The ship example above just shows that not everyone understands Cumulative Error
I have to work with a mix of metric and imperial fasteners and I find both are fine, for the whiners I'll point out that one pitch gauge set covers all Metric threads and I need several for Imperial (Yes, that's what the Inch system is actually called Imperial )

As mentioned before, "not metric" is often called "imperial", but unless it the version used by the UK and related, it's not "imperial".

I agree with Harold, I've never needed more than one pitch gage. Or are you lumping in things like Whitworth? And even if I did, so what? The problem I stated is that you are likely to see any of the pitches on that gauge that is roughly in scale for a given diameter actually USED by someone on that diameter. Several nominal metric size fasteners have 3, 4, or more pitches in fairly common use. Some depending on country of origin, others within a given country. And there are some really odd metric thread pitches too, with lots of "leafs". IIRC, more than in my standard "has never failed me" pitch gauge.

The metric system itself has many fine well known features vastly superior to not-metric. However, the application of the metric system outside of science and engineering (where the conversion simplicity is and exceptional quality) is hugely flawed; in my experience, more than non-metric. At least the common man can depend on 2 fastener pitches for any given size covering anything we will likely come across.

And of course it's the system I know and prefer, so of course it's the better system...

[SteveHGraham]

I should have known better than to indulge my hatred of imperial units on the forum again. Apologies to all.

And SI. Every product container I can find in the house is labeled with both SI and customary units.

Funny thing happened to me the other day. Someone mentioned SI, and I had no idea what it was. I spent 5 years studying physics, and all I remember hearing are "mks" and "cgs." I had to look SI up to see what it meant. I wonder if engineers use the term more than physicists. It would be just like them to pull something like that.

I still don't know what SI stands for. I will check. Hmm. It stands for "International System of Units." Okay. I would call that "ISU," but whatever. Maybe it comes from French.

Engineers are very weird, and I'm not just referring to the way they dress. I've been learning strength of materials (engineering subject) for fun, and I can't believe the nutty things engineers do. I did a problem where the letter W appeared as a variable. I kept staring at it, trying to figure out what it meant without looking at the solution. Turned out it meant "weight." It's hard to make myself think of weight as a single variable. To me, it was always mass times the acceleration due to gravity.

They even have a term called "specific weight." What? I had to look it up. It's density multiplied by g.

[John Hasler]

Russ writes:
At least the common man can depend on 2 fastener pitches
for any given size covering anything we will likely come across.

https://en.wikipedia.org/wiki/ISO_metri ... rred_sizes

Don't forget tolerance classes, which are usually ignored by maintenance people replacing hardware. ISO doesn't seem to have them (which is not necessarily good).

BTW while converting a single length measurement between ISO and Customary/Imperial is easy, properly handling rounding and tolerances so as to avoid the sort of stack-up described by Mr Ron is not. I believe that NIST has a document describing the correct way to do it.

[GlennW]

Don't forget tolerance classes, which are usually ignored by maintenance people replacing hardware. ISO doesn't seem to have them (which is not necessarily good)

They don't??

External Tolerances:
Pitch Dia.: 4,5,6,7,8,9
Major Dia.: 4,6,8
Position: e,f,g,h

Internal Tolerances:
Pitch Dia.: 4,5,6,7,8
Minor Dia.: 4,5,6,7,8
Position: G,H

This should simplify it...

metricmottoleng.GIF (4 KiB) Viewed 5022 times

metricskrtoleng.GIF (4.27 KiB) Viewed 5022 times

As for pitch gauges, I have three. One for US, one for Metric, and one for British.

[John Hasler]

"SI" does come from the French: Système international (d'unités). The French invented the metric system, after all, and the BIPM is in France. Also during the period starting in 1875 when the formal international system was developed French was the standard diplomatic language.

It's probably more appropriate to refer to ISO standards than to SI for engineering purposes. SI is all about making sure that the national metrology labs agree on the fundamental units. ISO publishes standards dealing with messy details such as screw threads.

It's only mechanicals and civils that use wacky units and notation. Electricals are sensible (though it does make sense that civils care about weight. You kind of want them to when they are designing bridges).