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Metric thread callout

That does not make any sense. There needs to be a number before the "H". Example - M8 x 1.75 6h.** But now you've got me curious about a 2mm diameter thread bearing a 2mm pitch! What the... ?

** - Small "h" is for external threads and capital "H" is for internal ones.
 
Zahnradkopf - you are right as far as ISO-H goes. Somebody made up something. Most likely US drawing. As far as M2x2 goes - another blunder by ANSI. I have said it many times - No pitch should be listed for coarse. The whole industrial world does it that way. Only in the US are we allowed to list the pitch on standard coarse and that will always be a reason for a screw-up. Some clowns just can not understand why they should not list a pitch for standard coarse. If it says M2 - than that is standard coarse. If it says M2 x 0.2 than I know that is a M2 fine thread with a 0.2mm pitch. Period! If it says M2 x 5, than that is a standard M2 coarse x 5mm long. If it say M2 x 0.2 x 5 than that is M2 fine with 0.2mm pitch, 5mm long.
99% of all metric threads used are standard and you should not even be looking for a pitch. You should not even have a fine pitch die or tap in your shop. The only time you will need one is if the customer wants it for one reason or another. Believe me - most of the time when you ask why they want a fine thread - they have no answer.
Metric thread was designed to cut down on all those goofy threads with a million different pitches.
M2x2 simply means M2 coarse x 2mm long.
 
Conduit threads, spark plug threads and one hell of a lot of car parts all use finer than std metric coarse threads, might be uncommon to you, but im happy to bet most people own a lot of things with metric fine threads in em!
 
I received a print with the thread spec being M2x2 ISO-H.

Try as I may I cannot determine what ISO-H means.

Tom

Edit: Opps! Thread is M16x2 ISO-H

I'd say that was a callout by somebody with NFI what they're doing, you're right to question it. I'll assume they at least got the H correct and it's a threaded hole right?

Number(s) are missing on the thread tolerance information that you will need. That should either read "ISO 1(2)(3)" or "6(5)H". However where fit is not specified or not important, convention is to assume it to be 6H. Let me know if you need those actual numbers for 6H and I'll look them up for you.

That is a standard metric coarse thread, and the pitch is not required. While it can be included, generally it is omitted, since to include it creates confusion. Convention is to leave it off if it's metric coarse,(as this is), and include it only if it's anything else. Anyone machining in a metric country will question a pitch callout on a metric coarse thread, as either the draftsman was a moron with NFI what they were doing, or they've made a mistake and the pitch should be something else. It would most likely instead be assumed to be the thread length, but general confusion and carnage would be created all around.

For anyone in the US who needs to deal with this type of thing on the shop floor, I can thoroughly recommend this book Engineers Black Book: Machinist and Manufacturing Reference Book It is an Australian publication, so if you buy a copy you just doubled our annual manufactured exports! Buy the METRIC EDITION and don't screw around with the US edition bullshit, I've never read the latter, but I can just imagine it as a bastardisation of what you really need for metric. You will have pretty much all the information you'll need in a spiral bound book with plastic coated pages that is designed to be used at a machine, and not some idiot's desk. I have no connection to the company, other than having (literally) worn out my copy of the book.

Hopefully that helps.
 
Adama-for your info - conduit threads, spark plug threads, oil drilling pipe thread, gas bottle threads, medical threads etc etc - those are very special threads. Most do not even have a 60 deg. angle. Those threads have nothing to do with standard metric thread. Some companies will for what ever reason put a special fine thread on their product. Sometimes the may have a valid reason. Other times it's just to make you buy replacements from them. That is no reason you should even have tooling for it in your shop. If you ever needed a "Fine" tap or die - it is just a phone call away. In a standard shop there should only be M2, M3, M4, M5, M6, M8, M10, M12, M16.
If you are into big stuff than may be M20, M24 and M30. You don't even need to know the pitch. What for?
Only one reason: If you need to drill tap holes and don't have a table for that, than you need to look up the pitch so you can subtract it from the nominal size to get the hole size for tapping. But that is the job of your engineering dep't.In a short time all your people will remember the tap hole size for any given thread.
After some time your designers will be happy to just call for M2, M3, M4, M5 etc. and your shop will be happy to just ask for a M2, M3, M4, M5 etc. tap or die. If they would see a print with M6x0.5 than they would know - this is a "Fine" thread and treat it as a special.
Ps.: There are some everyday so called "Fist" rules to determine the tap hole size. Multiply by 0.8! M2x0.8=1.6,
M4x0.8=3.2, M6x0.8=4.8. When you get to bigger sizes than add 0.1 and later 0.2. It is not that critical.
 
I get tired of hearing the same claim about metric threads, that the coarse series is so convenient because it serves all needs. BULLSHIT. Fine threads are for vibration tightness needed on airplanes and other engine-powered high speed creations, and secondarily they are used for adjustment. The establishment of the fine-pitch series by the SAE answered that purpose, and the fine metric pitches have been its European counterpart. We use a number of metric threads in our work (specified by our European clientele, all of whom, incidentally, are design engineers) and not one is coarse pitch. I cannot understand why anybody would insist that's an aberration. It's not, it's common sense.
 
Multiply by 0.8! M2x0.8=1.6,
M4x0.8=3.2, M6x0.8=4.8. When you get to bigger sizes than add 0.1 and later 0.2. It is not that critical.

If you are going to tap a 4.8mm hole with M6, then you are going break the tap for sure. Make a print out for metric threads and tape it to your shops wall. Simple.

But one thing you are correct juergenwt, on drawings metric threads don't have a thread pitch described, unless, its a fine pitch thread.


TDegenhart , here is a simple chart for you.
 
I get tired of hearing the same claim about metric threads, that the coarse series is so convenient because it serves all needs. BULLSHIT. Fine threads are for vibration tightness needed on airplanes and other engine-powered high speed creations, and secondarily they are used for adjustment. The establishment of the fine-pitch series by the SAE answered that purpose, and the fine metric pitches have been its European counterpart. We use a number of metric threads in our work (specified by our European clientele, all of whom, incidentally, are design engineers) and not one is coarse pitch. I cannot understand why anybody would insist that's an aberration. It's not, it's common sense.

Well I'll see your bullshit and raise it one, because what you just said is crap. UNJ is the standard thread used in most aircraft components, and that's a coarse thread my friend. Are fine threads use? Hell yes! Very common, but the MOST common in that field is the equivalent on UNC with a modified root radius ie UNJC

Likewise even in the automotive field, where Metric Fine threads are VERY common, I think you'd still find if you were to strip a vehicle and count the number of fasteners, assorting them to fine or coarse, I think you would be surprised by the number of standard metric coarse threads used. i haven't ever done it, but would expect them to still outnumber metric fine.

However the two fields are relatively specialised in the grand scheme of things. What "juergenwt" says is generally right. I have a relatively well equipped workshop and use metric exclusively. I do of course have BSW, BSF, UNC, UNF, and various pipe threads etc etc etc as taps. In metric I have ONE that is metric fine, and that is a 10 x 1 mm. The reason is it's used on all bicycles. I'm about to buy another metric fine tap as an adjuster, just as you suggested, but again that's specialised and I haven't decided what size will be used as yet.

How much metric fine you'll therefore see will depend on what field you're in. But in general engineering, almost never!
 
How much metric fine you'll therefore see will depend on what field you're in. But in general engineering, almost never!

Beg to differ......
Most pneumatic cylinders, hydraulic cylinders, barrel proximity sensors, etc have fine pitched metric threads when the connection size is larger than M6.
 
Beg to differ......
Most pneumatic cylinders, hydraulic cylinders, barrel proximity sensors, etc have fine pitched metric threads when the connection size is larger than M6.

Yeeesss, and do you think that's all aircraft are made of? Maybe you missed this bit:
Are fine threads use? Hell yes! Very common, but the MOST common in that field is the equivalent on UNC with a modified root radius ie UNJC

I should add that I'm no longer a hanger-rat, and it's been a long time since I've wrenched my way around aircraft. These days I'm kept busy breaking them and leave somebody else to fix them ;) Maybe things have changed recently, but that's partly how I paid for my licence, and the bug-smashers I worked on were all US designed/built so UNJ threads. The French thing I currently enjoy may well be different, I'll pay more attention next time something falls off!

Regardless, that's quite a specialised field, so let's just say every single fastener in an aircraft was indeed fine thread, unless you worked in that field it's very unlikely you'd come across a J form thread, fine or otherwise. The point being that outside of specialist areas like this, automotive, and a few other areas, you're not too likely to have to deal with metric fine very often. If you did happen to work in one of those fields it may apper as if the fine series are quite common just because of the exposure. You might think J series everywhere in the world too! ;)
 
Adama-for your info - conduit threads, spark plug threads, oil drilling pipe thread, gas bottle threads, medical threads etc etc - those are very special threads. Most do not even have a 60 deg. angle. In a standard shop there should only be M2, M3, M4, M5, M6, M8, M10, M12, M16.
If you are into big stuff than may be M20, M24 and M30. You don't even need to know the pitch. What for?

No disrespect, but you really don't have a fucking clue man, so STFU. All TCMT11 sized and CCMT 06 sized tool holders use M2.5, over here M3.5 is a std size used in electrical sockets. M14 is common too! M18 is rare but also encountered once in a while. Conduit over here Uses PG threads which are metric fine. Spark plugs the world over at least in any car or truck i have encountered are also metric fine normally M14. They all use a std 60 degree thread form. Yeah gas threads are not, but i never claimed they were. Were good old BSP not this NPT crap! Its also the only thread form in modern use with a 55 degree thread over here.

Seeing as most of the rest of the world uses metric, its patronizing at least to be told by a silly wanker of a american, that at best just represents some 300 million of the worlds 7 billion population what the norms are. When we have you out numbered a good 20x over!

FYI your multiply rule is completly fucking wrong like the rest of your crap, tap drill size for M6x0.8 is 5.2, not 4.8 numb nuts! You just subtract pitch to get tap drill size, not multiply + add some random shit! Its simple, but thats probaly why you don't get it! Yeah in a lot of cases its then rounded down the nearest whole 0.1mm aka for M12x1.75 you use a 10.2mm drill, allowing for drilling tolerances it works fine.
 
Ps.: There are some everyday so called "Fist" rules to determine the tap hole size. Multiply by 0.8! M2x0.8=1.6,
M4x0.8=3.2, M6x0.8=4.8. When you get to bigger sizes than add 0.1 and later 0.2. It is not that critical.
Is "Fist" short hand for "ham fisted"? Good luck with that M6 tap.

No charts or multiplication needed. Diameter - pitch = tap drill.
 
A standard, off the shelf, tap will be 6H and a standard die 6g.
Standard call outs of metric threads are supposed to be 6H/6g.

Agreed, my guess is either they've forgotten to write a "2" after ISO (assuming it was an ISO 2 tolerance required), orrrr they mean ISO to be M form ie metric 60 degree, and they forgot to write "6" before the H. Either way that calll out sucks as it is, and I don't think you could ever be 100% sure what they meant without going back to ask. Hopefully the OP will let us know at the end of it.

I sure hope this doesn't degenerate into a typical metric bashing bullshit session!
 
Petef: How much metric fine you'll therefore see will depend on what field you're in. But in general engineering, almost never!

Tonytn36 :Beg to differ......
Most pneumatic cylinders, hydraulic cylinders, barrel proximity sensors, etc have fine pitched metric threads when the connection size is larger than M6.

Petef: Yeeesss, and do you think that's all aircraft are made of?

CRM?
 
This is the worst reply that I have ever read.

Zahnradkopf - you are right as far as ISO-H goes. Somebody made up something. Most likely US drawing. As far as M2x2 goes - another blunder by ANSI. I have said it many times - No pitch should be listed for coarse. The whole industrial world does it that way. Only in the US are we allowed to list the pitch on standard coarse and that will always be a reason for a screw-up. Some clowns just can not understand why they should not list a pitch for standard coarse. If it says M2 - than that is standard coarse. If it says M2 x 0.2 than I know that is a M2 fine thread with a 0.2mm pitch. Period! If it says M2 x 5, than that is a standard M2 coarse x 5mm long. If it say M2 x 0.2 x 5 than that is M2 fine with 0.2mm pitch, 5mm long.
99% of all metric threads used are standard and you should not even be looking for a pitch. You should not even have a fine pitch die or tap in your shop. The only time you will need one is if the customer wants it for one reason or another. Believe me - most of the time when you ask why they want a fine thread - they have no answer.
Metric thread was designed to cut down on all those goofy threads with a million different pitches.
M2x2 simply means M2 coarse x 2mm long.

Products are getting more compact and smaller everyday.Designers are forced to fit fasteners in tighter places.To say that a shop should not even have a fine pitch metric tap in house is ridiculous.I have worked on metric parts that are worth 50 thousand dollare that I had to tap.I will guarantee that I would have been fired on the spot if I had tapped a course thread ,if the customer wanted a fine thread ,even tho the rest of the world says that I am right.I am curantly reworking product and tooling has been sourced from all over the world (reshoring)I find course and fine metric and USA threads.Welcome to the real world.Edwin Dirnbeck
 
Edwin - did you read my post? Read it again! →"The only time you will need one is if the customer wants it for one reason or another". How many "Metric fine threads" are you going to stock? If you want to waste your money - go right ahead. As far as I am concerned - if I need one for a job where a customer wants to have a fine thread - I order one!
 
No disrespect, but you really don't have a fucking clue man, so STFU. All TCMT11 sized and CCMT 06 sized tool holders use M2.5, over here M3.5 is a std size used in electrical sockets. M14 is common too! M18 is rare but also encountered once in a while. Conduit over here Uses PG threads which are metric fine. Spark plugs the world over at least in any car or truck i have encountered are also metric fine normally M14. They all use a std 60 degree thread form. Yeah gas threads are not, but i never claimed they were. Were good old BSP not this NPT crap! Its also the only thread form in modern use with a 55 degree thread over here.

Seeing as most of the rest of the world uses metric, its patronizing at least to be told by a silly wanker of a american, that at best just represents some 300 million of the worlds 7 billion population what the norms are. When we have you out numbered a good 20x over!

FYI your multiply rule is completly fucking wrong like the rest of your crap, tap drill size for M6x0.8 is 5.2, not 4.8 numb nuts! You just subtract pitch to get tap drill size, not multiply + add some random shit! Its simple, but thats probaly why you don't get it! Yeah in a lot of cases its then rounded down the nearest whole 0.1mm aka for M12x1.75 you use a 10.2mm drill, allowing for drilling tolerances it works fine.

Adama- No disrespect, but there is no need to answer your post. It speaks for itself.
 








 
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