metric drill set explained?

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Magicniner
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Re: metric drill set explained?

Post by Magicniner » Thu Oct 04, 2018 12:08 pm

BadDog wrote:
Thu Oct 04, 2018 10:22 am
Several nominal metric size fasteners have 3, 4, or more pitches in fairly common use.
So you've never encountered 1/2" UNC, 1/2" UNF and 1/2" UNEF and variants in the same size? :D
You should get out more ;-)

John Hasler
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Re: metric drill set explained?

Post by John Hasler » Thu Oct 04, 2018 12:16 pm

GlennW wrote:
Thu Oct 04, 2018 11:47 am
John Hasler wrote:
Thu Oct 04, 2018 11:25 am
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
I know they specify tolerances. I mean tolerance classes: https://en.wikipedia.org/wiki/Unified_T ... ce_classes

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BadDog
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Re: metric drill set explained?

Post by BadDog » Thu Oct 04, 2018 12:20 pm

John Hasler wrote:
Thu Oct 04, 2018 11:25 am
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).
LOL. Fair enough, but again, "common man". Other than missile systems machinists ordering or making to exacting specifications, or guys restoring/repairing aircraft systems, most of use don't have concern for that in day to day (home or otherwise) shop projects. And as Glenn pointed out, metric has the same range of specifications, so the multiplier effect applies to both. But given the larger magnitude of metric fasteners to already required, after applying all that equivalently (modulo classes maybe?), it just makes metric fasteners all the more onerous in my view.

So it doesn't really come up when you are talking about fastener stock on hand, or going to the local fastener supply where grade and coarse/fine are generally the only points of discussion beyond dimensional/drive requirements, unless you want metric. In a store where 30% of the stock is "standard", buy you have a 99.9% chance of having what you need, vs all that extra metric stock, and you still have only about a 70% chance (in my limited experience) of laying hands on what you need. The odds get much worse with my in-shop stock.

Anyway, I'm going to try to refrain from further comment on the subject. Home shop work in metric or standard makes little difference unless you have prints in one system, and machines in another. Or worse yet, prints for some *parts* in one system, with others in another. Then conversion and rounding along with stack-up are just a fact of life. Engineers and physicists (and other scientists) have solid arguments for preferring the SI/ISO/metric system of units, and I fully support that. But it's in the world of fasteners where my loathing of "metric" has it's tangled roots. And I would argue that's where it affects us "home shop" types most. Wire/Letter/Fractional vs Metric drills (etc) relative to the OP have it's own set of issue on both sides, though I will add that other than for optimal tap thread depth (particularly on very small), most of us could live quite comfortably with only a set of fractional by 64ths to 1/64th. And yes, I'm ignoring jets and other such intentionally, but that probably doesn't apply to *most* of us, or most of our work.
Last edited by BadDog on Thu Oct 04, 2018 12:28 pm, edited 1 time in total.
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BadDog
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Re: metric drill set explained?

Post by BadDog » Thu Oct 04, 2018 12:24 pm

Magicniner wrote:
Thu Oct 04, 2018 12:08 pm
So you've never encountered 1/2" UNC, 1/2" UNF and 1/2" UNEF and variants in the same size? :D
You should get out more ;-)
Not in any practical way, and maybe, if I lived in the UK. I've encountered them with about the same frequency as "lock in" pitches, which is to say very VERY rarely. And not something anyone I know (US) would even consider stocking in-shop, or expect the local fastener store to carry (though they may?) I don't think I've ever encountered an EF in "real life" (automotive, home, etc). I seem to encounter the metric pitch variety pain almost every time I have to deal with it (ok, probably 10-20% realistically). That's not even apples and oranges. More like apples and plantains.
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GlennW
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Re: metric drill set explained?

Post by GlennW » Thu Oct 04, 2018 12:33 pm

John Hasler wrote:
Thu Oct 04, 2018 12:16 pm
I know they specify tolerances. I mean tolerance classes: https://en.wikipedia.org/wiki/Unified_T ... ce_classes
So, you are referring to the fact that ISO doesn't use the actual word "Class" but instead uses a number and a letter to represent the same.
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Re: metric drill set explained?

Post by John Hasler » Thu Oct 04, 2018 1:09 pm

In my experience UNF is common in engines, machinery (lug nuts are UNF), and electronics. I've run across UNEF in instruments and optics.

Then there is UNJ: https://www.threadcheck.com/whats-the-j ... nicalinfo/

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Re: metric drill set explained?

Post by John Hasler » Thu Oct 04, 2018 1:10 pm

GlennW wrote:
Thu Oct 04, 2018 12:33 pm
John Hasler wrote:
Thu Oct 04, 2018 12:16 pm
I know they specify tolerances. I mean tolerance classes: https://en.wikipedia.org/wiki/Unified_T ... ce_classes
So, you are referring to the fact that ISO doesn't use the actual word "Class" but instead uses a number and a letter to represent the same.
I can't find anything equivalent to the UN "classes" but I would not be surprised if it existed. Do you have a link?

[Edit] https://www.fastenal.com/content/feds/p ... ations.pdf
Last edited by John Hasler on Thu Oct 04, 2018 2:34 pm, edited 3 times in total.

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GlennW
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Re: metric drill set explained?

Post by GlennW » Thu Oct 04, 2018 1:19 pm

Here's a quick google search.

https://www.engineersedge.com/hardware/ ... sizes1.htm

The above chart shows "standard" ISO hardware class, which I would estimate to be the same as US Class 2.

I use software for threading and you select the ISO number and letter designation for the desired fit (class) and it gives me the associated tolerances, so I don't have a specific chart. Perhaps there is better info in Machinists Handbook.
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BadDog
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Re: metric drill set explained?

Post by BadDog » Thu Oct 04, 2018 1:29 pm

Maybe I ran across it and didn't recognize it. In fact, I didn't realize lug nuts are UNF. But lug studs and nuts are specialty fasteners in my book anyway. Splines, lengths, cones, shoulders, it all varies by manufacturer, vehicle, weight, etc anyway. And instruments are among the bastards I mentioned, optics too, lead screws, vises, all "specialty"; they could be anything, metric or otherwise, and it wouldn't matter as the goal there is to fit a purpose (including lock-in for some) rather than be a standard fastener. But those are not the fasteners any of us keep on hand or need access to in the daily process. A bolt damaged or twisted off on an alternator bracket, the engine-frame brackets on my Kubota, or the backhoe brackets on the back of it (both cases included missing and broken, but different not-interchangeable fasteners), and so on. That's what I need to be able to pull from my bin to finish a job, or failing that, run to the local large industrial fastener supply to pick them up. And when the fasteners are metric, that process all too often still fails to produce what I need.

Ok, now I'm really stopping. No, seriously... :roll: :lol:
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Re: metric drill set explained?

Post by Harold_V » Thu Oct 04, 2018 3:34 pm

BadDog wrote:
Thu Oct 04, 2018 1:29 pm
In fact, I didn't realize lug nuts are UNF.
SAE (Society of Automotive Engineers)

H
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BadDog
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Re: metric drill set explained?

Post by BadDog » Thu Oct 04, 2018 4:10 pm

Ahh, just not used to seeing it in that term. My head processed it as "other". Not sure why "U" didn't register as "Unified". So just standard/SAE fine, which makes it irrelevant as a response to my point. Not sure what to say. I know "extra fine" exists as a standard, but from my clearly faulty memory, I don't recall ever running across one (at least that I recognized as such). And for some sizes, I don't have many if any fine either, and it still almost never causes me problems with standard threaded fasteners (and I know I can get it right down the road). Metric fasteners, well...

Most of the time you take it out, and you put it back, maybe looking up torque specs or applying anti seize or locking compound as appropriate. You don't really notice the problems unless you break/lose one, or need a longer one to suit some modification.

Dang it! I did it again... ;)
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Re: metric drill set explained?

Post by Harold_V » Fri Oct 05, 2018 1:55 am

National course, or USS (United State Standard, also known as Sellers Standard Thread)
National fine, or SAE (Society of Automotive Engineers).
In truth, there's a myriad of bastard threads in our society, often due to a manufacturer preferring to use proprietary fasteners, ignoring the standards that allow for interchangeability. Holds the consumer hostage, often accompanied by exorbitant prices. A good reason to avoid buying their products.

It's hard to beat the thread schedules in Machinery's Handbook, and when you feel you really must bone up on threads, the H28 manuals are the bible.

H
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