Mixing measurement systems, bad idea, or really bad idea?

I work in imperial and try to avoid metric tools, but I will admit that imperial is an asinine antiquated system. Dividing a foot into 12 smaller units is silly, and I don't understand why anyone ever thought that using binary fractions (1/2, 1/4....) rather than decimal numbers was a good idea. I guess that is dates to the 18th century (or earlier) when a unit of length could be easily divided in half using a compass but there was no simple way to divide a unit of length by 10.
 
Machne screws increase in diameter by .013" for each number size starting with #0 @ .060". To find the size of a given screw, multiply the screw swize by .013" and ad .060". A #6 will be 6 x .013" = .060" = .138" and a #10 will be 10 x .013" + .060 = .190", for example. Listed fractional sizes are approximations.
 
The size of machuine screws continues on the lower end with #00, #000, and #000 being .047", .034", and .021", respectively.
 
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BTW, how big are #6, #8 and #10 machine screws again?

A while back, I posted a homemade chart showing decimal equivs for machine screws and small metric fasteners. Probably lost by now, though. Machine screws follow an archaic system that makes sense if you follow the system. It does not fit into our modern measurement system, and is often duplicated by fractional sizes. Almost, within a couple of thou anyway.

Machine screws have a base size of 0.060 in. Why? I don't know, but that's the system. For each size, add 0.013 in. A 1-64 machine screw is 0.060 plus (1x)0.013 = 0.073 in dia. A 2-56 = .068 + (2x.013) .026 = 0.086. Again, why .013? There are thread sizes at 8 TPI intervals, again, why? Who knows, the system is lost in antiquity. Maybe a very old copy of Machinist's Handbook could shed some light. But me, I don't care unless I run into one, a rarity these days.

And so on up the chart... A 6-32 screw is 0.060+(6x.013)=.138 Convienetly, a Nr 5 screw is 0.125 in, 1/8th. A Nr 8 is .060 +(8x.013) = 0.164 in. A Nr 10 is at 0.190, with a 3/16" at .1875. Most hardware stores use one and call it the other. Maybe that has some bearing on the [why] of 0.013. 1/4 in vs Nr 14 is just a few thou different.

The old school system goes far above 1/4 in, almost to 3/8 in. Modern sizing has taken over most sizes above 1/4 in, with Nr 12s being still in use but rare. There are(were) other sizes of fractional, as well. I recently acquired taps for 1/16-80. At 0.0625 vs 0.060, they will almost work interchangably. Almost ... ...

I personally work with tiny sizes, less than Nr 0. Nr 00 or 2/0 steps down the same way, at -.013=0.047 in. There are several sizes smaller, optical screws and the like. 3/0 is the smallest size I work with, but there are several smaller. Then there's metric, re: modern eye glasses. If you pursue it much further, all I can do is wish you luck.

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I guess I needed to be more explicit about the #6, #8 and #10 machine screws. My point was that working in "Imperial" with Imperial fasteners involves a hodgepodge of fractions, thousandths of an inch and arbitrary archaic anachronisms like the numbered screws. Designing or laying out a part with tight clearances can be crazy-making.

Working in metric with metric fasteners is wonderfully boring by comparison.

Craig
 
I guess I needed to be more explicit about the #6, #8 and #10 machine screws. My point was that working in "Imperial" with Imperial fasteners involves a hodgepodge of fractions, thousandths of an inch and arbitrary archaic anachronisms like the numbered screws. Designing or laying out a part with tight clearances can be crazy-making.

Working in metric with metric fasteners is wonderfully boring by comparison.

Craig


Sure metric is easy, nice whole numbers 8mm, 9mm oh wait where did these 1.2mm, 1.6mm, and 2.5mm etc bolts come from. Are they DIN, JIS or ANSI spec bolts? :grin:

The metric system is relatively simple when you ignore the human element. Human's love to make the simple complex.
 
I worked at procuring parts for large shops for 40+ years where we dealt with roughly equal amounts of metric and imperial fasteners, parts, and tooling. That was because that was where manufacturing was during that time period. We got used to it as it morphed. It has now swayed more to metric in the U. S., and is continuing in the rest of the world. One thing I can guarantee you. You will not be able to decide which ways major manufacturers will go. If you work in industries like heavy equipment repair, fleets of large and smaller trucks and automobiles, all kinds of ancillary equipment like tampers, pumps, mowers, road building equipment, and so forth, procuring parts needed to keep them all in service, you would understand that we cannot stem tides like that. If they come up with a "new and improved" (and proprietary) system tomorrow to "replace them all", then we will have to learn a new system to add to the list we are already trying to keep track of. And procure the tools to work on them. We are in a position of reacting, and we will not change the future by resisting. We will only be left behind. Like our Whitworth tools. With CNC machines, and the widespread use of making parts as needed, we may get to a point where nothing is interchangeable, and only the maker who sold the equipment will have access to the records kept while they changed part sizing and custom thread pitches and forms for each and every new piece of equipment, and would be happy to sell you some parts made on site to fit that specific serial number ONLY. Ultimate proprietary equipment, keeping the competition out of your knickers. Or maybe not, or maybe something scarier yet... Do not underestimate the potential of greed mixed with new capabilities.
 
I use mixed measurements all the time (metric sockets on a 1/4” ratchet). Also my tailstock ram is marked in either .2” or 5 mm depending on what I need (close enough to the same thing for most purposes).
 
Being tool poor I am always on the lookout for cheap tools. Today I found them. 2 dial indicators and a test indicator for $10 each. Brand name too. But then I looked close and they are that funny European measuring system that will never catch on. M m m m m metric. Now I need to drink something to get the taste out of my mouth.

...

But seriously, will cats and dogs live peacefully together if I give these tools a home? Or will chaos consume my meager shop as I furiously multiply divide by 25.4 and wonder why my parts never measure up to spec?

Clearly the only way to be safe is to keep those dreadful things out of your shop! Oh ... and uh ... PM me the URLs for them so I can buy them?
 
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