The metric system

[Ol'fogasaurus]

I got curious after reading something the other day and after being told to learn the metric system; then it being cancelled after the requesters figured out just how much it would cost them (future backup/replacement parts from the inch to the metric system were the main problem for the change. Not sure what is being done right now metric or SAE) and cancelled the request I got interested again in the subject (the request for the metric system was before computers were in vogue).

https://interestingengineering.com/the- ... roglyphics

Here are some fax that I found interesting and... there is more stuff besides the metric system that is not relevant to the original question.

Lee

[GS guy]

FWIW, talk back in the 70's was that since the entire US manufacturing system was based on the Imperial measurement system, it just wasn't feasible financially to convert over - imagine replacing "every" machine tool at the time for one that operated in mm! Converting back and forth between mm-in became the order of the day - I'm sure giving many machinists nightmares! Since I grew up in the Imperial/English system, I still can't visualize metric sizes - except an easy one like 13mm. Have to convert from metric to inch in my mind to visualize the physical size. Inch-size fasteners I can usually identify just by looking at them.
I believe metric is better and would have been a much easier system to learn and work with, in fact most if not all scientific measurements are done in metric. That said, I decided to build my custom Deserter GS with Imperial fasteners due to the greater and easier availability of inch-based hardware.
I still wonder how the screw system went from inches and fractions of - to number screws: 6-32, 10-24, 1/4-20, etc. Screwy system!
Jeff

[Ol'fogasaurus]

I still wonder how the screw system went from inches and fractions of - to number screws: 6-32, 10-24, 1/4-20, etc. Screwy system!
Jeff

I am not supposed to do this but it is fairly easy to explain the coding as I done several designs that later became MIL standards (more than 7 for sure) bolt designs plus used a lot of the NAS (National Aerospace Standard) plus company owned designed fasteners drawing blueprints.

The basic design of the fastener (bolts vs. screws), that being the head design including the fluting if there is to be any, the under radius between the head and the shank/threads material and temper... just to name a few spec. things in the standard. The standard nuts, washers, et al, would be dictated similarly.

The dia. system in the coding of the fasteners is/was based in either16ths of an inch or 32nds of an inch hence hence a "-6" bolt would be 6-16ths of an inch (3/8ths) or 12-32nds of an inch as an example and for several different reasons.

The thread count would be next in the coding and is in "number-of-threads per inch" and how they were to be formed (cut or rolled). The same for the "shank", if there is one, and the "easy-on" taper at the end of the fasteners threads all part of the standard's coding.

The most common washer in the everyday market is probably based an AN/NAS style washer; example: AN960PD10 or maybe ending in10L (5/8th internal dia.). The translation would be a AN (Army-Navy) design, the PD (in this case is) is a plated finish and the number is the dia. of the hole in 16ths. The "L" indicates a thin washer vs. the normal thickness stated in the standard's design. It is also an NAS1149 plus coding if I remember correctly. Everything else information wise is buried in the standard itself.

The MIL and other standards numbers are really not supposed to be known or used in the public but so much of it is out there mostly because of ignorance or selfishness. The "standards" themselves are not short page wise and info wise. The standards may range from some pages to "what the..." sizes as there is a lot of things about the material, temper, shape design, tempering and other special design things.

Does this help?

Lee

[GS guy]

I get the AN system Lee, although I gather fasteners in that size designation are primarily used in aircraft/aerospace and not your typical hardware store stuff. What I don't understand is how smaller fasteners transitioned from being labeled - smaller than 1/4" - to 12, 10, 8, 6, 4, etc.
For instance, a 10-32 screw is definitely not the same as an AN-10 (5/8") bolt. A #10 screw is approximately 0.190" thread major diameter, close to 3/16" (0.187"), yet it's not called a -3 or #3 screw. It's not "10" of anything as far as I can tell, yet that's the common name. That naming convention has escaped my learning curve.
Jeff

[GS guy]

OK - I had to research this myself. The gist of it is screws smaller than 1/4" are measured in "gage" size, I guess similar to nails and such. And there's a formula to determine the diameter of a particular gage!
Here's the rest of the story:
https://themetricmaven.com/without-metr ... e-screwed/
Jeff

[Ol'fogasaurus]

I get the AN system Lee, although I gather fasteners in that size designation are primarily used in aircraft/aerospace and not your typical hardware store stuff. What I don't understand is how smaller fasteners transitioned from being labeled - smaller than 1/4" - to 12, 10, 8, 6, 4, etc.
For instance, a 10-32 screw is definitely not the same as an AN-10 (5/8") bolt. A #10 screw is approximately 0.190" thread major diameter, close to 3/16" (0.187"), yet it's not called a -3 or #3 screw. It's not "10" of anything as far as I can tell, yet that's the common name. That naming convention has escaped my learning curve.
Jeff

Screws are designed and indexed different but yet similar but as they all have specs to them. I am pretty sure that they (especially when dealing with grading like other fasteners have in part of the index) adhere to some national or international or design use specs but we are now starting to get into some very intricate discussions.

I never did draw up a design for a screw or nail as they are not strong enough for the loads we were required to deal with . I did (once) work on a specific "captured nut" which is even more different that a blind nut (or fastener) as it was a stamped to shape then threaded piece made of flat stock. You can find quite a few designs like this by doing a search on "captured nuts" but the one I dealt with isn't being made anymore... I guess it was just too unique.

I can't tell you how many fasteners (not screws in this case) look the same but it is the "innards" that change design and use limitation which is usually marked on the top of the head but not sure this is always as I remember. Also embedded in the design are process specs which do change the design but unless you have the basic design info you wouldn't know about it.

For instance: https://www.boltdepot.com/fastener-info ... %20rows%20 and there is so much not shown here that is or could be in constant change but "box stores" probably don't worry about it.

One of the fastener stores I go to for specific things does support the Boeing Company plant locally but only for mockup purposes only not for airplane assy. The fastener specialty stores we had locally that did do "the aircraft thing" plus was open to the public had to have an inventory so large and so detailed that the inventory taxes put them out of business. But those same fasteners were not specific just to aircraft but other things like cars and truck could and would use some of the same things. Just getting the fasteners made plus the number of many different test results (the number often tied to the number of fasteners ordered) per order puts the box stores and so many others out of the special design game.

Fasteners also have cycle lives and probably age limits also. Stuff most people don't realize until, for instance, when removing a nut, the split washer is now flat at the split area so that the locking capability of the washer for holding the nut in place ceases to work as it was designed to do... and one thinks that life is complicated...

IMG_2681 - Copy.JPG

IMG_2682 - Copy.JPG

I don't know if everyone are aware of this used for fastener dia. and thread checking but the dark size and thread count screws are metric and the silver ones are SAE (threaded inside and outside) and are used for identifying the fastener or nut threading. Most, but probably not all, stores that carry nuts and bolts (et al) might carry this string. I got this years ago at my local Ace store and I payed something like $35 for it (that is my memory of the price anyway).

Lee

[GS guy]

Looks like a handy tool Lee! I heavily rely on an old Cleveland Twist Drill decimal equivalent chart. Measure the major thread diameter with a caliper then locate it on the chart. Determining thread pitch is a bit trickier! My stock of various size SAE hardware provides plenty of "test" samples to compare to. My metric stock isn't so well organized.
Jeff

[SCOTTRODS]

We have had, in many of my work places, a "yard stick" looking piece with studs for nut check and threaded holes or raised ferrules with threads in them... These are available if I remember right (maybe even on Amazon) through most hardware sales companies like Fastenal or McMaster... but they're kinda expensive. I'fe seen about 6 different ways to check for correct fastener size and thread pitch... but the yard stick thing is my favorite.

[Ol'fogasaurus]

We have had, in many of my work places, a "yard stick" looking piece with studs for nut check and threaded holes or raised ferrules with threads in them... These are available if I remember right (maybe even on Amazon) through most hardware sales companies like Fastenal or McMaster... but they're kinda expensive. I'fe seen about 6 different ways to check for correct fastener size and thread pitch... but the yard stick thing is my favorite.

Is this what you were talking about? It is a lot more expensive than the $29 thing I was talking about.

Lee

[SCOTTRODS]

That's the one, Lee. Usually the Hardware companies that we had in places I've worked charged less for them if you were buying shelf stock constantly (Sometimes complimentary even). I mentioned they were a bit more expensive... I think I was right! LOL OUCH!

The problem of course still exists, on these... they really have a limitation to the possibilities of threads and sizes... This one stops at 12mm and 1/2 inch sizes and doesn't include odd thread pitches... there's a ton of them. But the reason I like these is that I can visualize Quickly without having to sift through the string of sizes. I;ve used both and they're ALL very useful. And for the average day, these cover most things I ran across. Once I hit a wall with these I had an excuse for how long the job took...LOL - truly sometimes it was a proprietary fastener in several ways including things like having a shear section or a specific length Unthreaded portion or washer head with serrations and in aricraft the drilled for safety wire and other specs (which you keep alluding to) that are not typoical to these suppliers I mentioned. In aviation the companies I worked for bought all their hardware either directly from the manufacturers (boeing for example) or from a company that sold Aerospace hardware Such as Aviall.

I've been enjoying the discussion on this from afar till we got to the identifier tools. We had a plastic identifier at the last place I worked. I hated it, but it worked for the most part, until someone checked thread pitch on a metirc with the Standard thread check side, and it was such a Close Match that they assumed the SAE size with a glance (Especially in the smaller sizes) and ordered the wrong damn screws... in larger fasteners it wasn't as likely to happen. When I say someone... it might have been me a time or two... <duckiing out>

[Ol'fogasaurus]

I retired in Nov of 2000 so I am not sure what is going on as things do change very quickly but I don't think the way basic spec are written up for fasteners... of any type will change, other than other designs are always being added and that they are not on paper anymore.

If you ever got to see the basic writeup specs on any particular fastener other than the tables your jaw would drop and head would spin as some are close to being a book vs. a short writeup. Some are very simple in dialogue comparatively to what others are . In the specs there are other specs within them and are either in blue or in a different font which means you have to go to that spec for more info and it too might have other specs berried in it for you to search other wise the original spec would be being rewritten almost day by day (an exaggeration but not that much of one either).

I did find some more test devises for sale designed for checking things; some are simple plastic or thin metal and much cheaper but testing the wrong thread by someone who doesn't have that lightness of touch can cross-thread and obliterates the plastic of the tool.

Down at the local hardware store you can often see the "ham handed" (not meant to be insulting to any one just the term used by the business as they were replacing the testing pieces) when jamming things in while trying to figure things out.

The ones that I drew the drawing for as company designs took maybe a year of two before the different no-company version specs were dropped in front of me by the engineer I was assigned to at the time (he had a big grin!).

Lee

[Dale M.]

Just learn to work within both system, forget all the technical BS and just understand diameters, thread pitch and torque values/specifications...

[Ol'fogasaurus]

Just learn to work within both system, forget all the technical BS and just understand diameters, thread pitch and torque values/specifications...

While size and thread count is very important to most of us but he technical BS is usually is the most important part of it. Knowing about the grades is very important and the markings, when on the bolt head, can be a short cut if you recognize them. The wrong bolt in the right place can be very dangerous.

Lee

[Dale M.]

I think that is what I said....

[Ol'fogasaurus]

I think that is what I said....

It was the second part of what I said was missing from what you said.

Dale, it is so easy just to get a bolt, nut and washer from a store but miss the strength that may or may not be needed in the design. I've seen people replace a shanked fastener (designed for shear) with the fully threaded fastener because it was cheaper not knowing that the strength and design of the replacement fastener was way less than what it replaced.

Lee