Talk:ISO metric screw thread

Too Technical
I came to this page as a layman hoping to learn more about screw threads - and even after reading the page I am little the wiser. The diagrams are extremely confusing, as they do not resemble screws as I know them and the diameter markings make no sense. What, for instance, is "Dmaj" the measurement of? According to the first diagram, it measures something beyond the physical dimensions of the screw. Furthermore, what is "nominal outer diameter?" Is this the diameter from thread-tip to thread-tip or from trough to trough? If so, it should state this explicitly rather than use jargon.

In short, I think this article could do with some major editing to make it more understandable. — Preceding unsigned comment added by Newzild (talk • contribs) 08:44, 2 October 2014 (UTC)


 * (I'll not edit the article at this time). The diagram is an extreme closeup of the business part of a screw inside a nut.  As is tradition in the industry, they only draw the part from the middle out, since the other half would be the same.  Dmaj or D is the "nominal" diameter, in other words, it is the size of the hole you would drill in something to just put the screw through to a nut on the other side.  D is also the diameter of the screw if the edges were perfectly razor sharp and not rounded off to avoid breaking.  Thus if you are making a one-off screw by cutting a thread in a steel rod, you would start with a diameter D rod, cut the grooves and finally file of the sharp edges (making the final screw slightly thinner).


 * Once you know those practicalities of mechanics, the article makes a lot more sense, explaining official rules that screws must not be too big for the hole in the nut, and nuts must not be to tight for the screws, so if a factory cannot make all their screws exactly the same size, they need to error on the side that won't get stuck. So to bolt together two pieces of wood with an M10 bolt and nut, you would use a 10mm drill, then just pop any brand of M10 bolt through the hole, cap it with any brand of M10 wafers and secure it with any brand of M10 nut.


 * The main point of the article is to explain the details that make metric screws different from other screws, such as UTS or BSW, each of which are different in those details. Jbohmdk (talk) 05:15, 19 September 2015 (UTC)

Engineering standards are an inherently technical topic, and simplification would reduce the value to technical readers. The warning should be removed and the article should not be modified.Jack — Preceding unsigned comment added by 129.127.236.130 (talk) 02:39, 25 January 2022 (UTC)


 * Such a lot of balls here. What are the clearance holes for male metric threads? This is EXACTLY THE KIND OF INFORMATION AN ENGINEER WILL NEED. Polymath uk (talk) 15:28, 24 January 2023 (UTC)

M0.8
May I know where to get the international standard for M0.8 pitch, major diameter, pitch diameter and minor diameter specification?


 * I don't know whether there is an ISO standard pitch for M0.8 (the pitch diameter and minor diameter are already standardized as a function of the pitch and major diameter by the formulas given in the article). The classic tables (ISO 261, ISO 262) all start at M1. You might want to ask ISO. Markus Kuhn (talk) 16:04, 16 August 2008 (UTC)

Bolt heads are off-topic
The added table columns on hexagonal bolt heads seem off-topic. This article is about screw threads, which are used on many other products than hexagonal nuts and bolts. This information, which isn't covered in the referenced screw-thread standards, could be moved to the articles on screw or bolted joint, and should have references to the relevant source standards. Markus Kuhn (talk) 10:56, 9 April 2009 (UTC)

the pitch is physically wrong
due to physic's methods the pitch should be expresed in mm/spin units —Preceding unsigned comment added by 190.38.150.30 (talk) 18:03, 10 July 2009 (UTC)
 * I disagree. "Spin" or "rotation" is a dimensionless quantity here, i.e. its unit is "1". The referenced standards specify the pitch of the threads using the unit millimetre. Markus Kuhn (talk) 12:07, 13 July 2009 (UTC)

H calculation
Should not the calculation for H be P/2 * sin(60)?

Also there is no mention of the concepts: root radius, root truncation, crown truncation, lead flank, trailing flank, lead angle, --71.38.172.8 (talk) 16:11, 1 February 2010 (UTC)


 * Nope, it's right. I've changed it to cos(30) just to match the ref, but it give the exact same value. As for your other points, please add the information if so inclined. Wizard191 (talk) 19:07, 1 February 2010 (UTC)


 * I went through the geometry, and I have $$H = \frac{P}{2} \cdot \frac{1}{\tan{ \frac{\pi}{6} }}$$. Incidentally, this is the same as $$H = \frac{ \sqrt{3} }{2} \cdot P$$. Mathfreak11235 (talk) 17:11, 17 December 2012 (UTC)


 * I agree with Mathfreak11235. Since you are using H and P, and also a half of the thread angle $$\frac{60^\circ}{2}=30^\circ$$, I believe that the relationship between H and P should be described as follows $$\tan(30^\circ)=\frac{P}{2H}$$. This expression is valid for any thread angle. — Preceding unsigned comment added by 148.202.58.146 (talk) 22:13, 7 June 2016 (UTC)

No formaly published academic review on.....
ISO 261 http://scholar.google.com/scholar?as_q=ISO+261&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=title&as_sauthors=&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en --222.64.17.90 (talk) 01:49, 31 July 2009 (UTC)

Papers of ISO 261 citations are not traceable http://scholar.google.com/scholar?start=0&q=allintitle:+ISO+262&hl=en

and yet the website of http://www.iec.ch/ is not traceable physically, other than email which is not sufficiently convince the readers--222.64.17.90 (talk) 02:00, 31 July 2009 (UTC) It's just the matter that the webmaster of the site needs to add the info of physical address

The org is there as referred by http://www.springerlink.com/content/r6137369018t47q0/ --222.64.17.90 (talk) 02:56, 31 July 2009 (UTC)

http://www.springerlink.com/content/8n12h4311606626k/

http://findit.lib.rmit.edu.au:9003/sfx_local?ctx_enc=info%3Aofi%2Fenc%3AUTF-8&ctx_id=10_1&ctx_tim=2009-07-31T13%3A10%3A2EST&ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fsfxit.com%3Acitation&rft.genre=journal&rft.jtitle=Chromatographia&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&sfx.title_search=contains&url_ctx_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Actx&url_ver=Z39.88-2004 --222.64.17.90 (talk) 03:13, 31 July 2009 (UTC)

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V4T-4S1C889-4&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2f0126b9a815a4b8e8b57cc3dd83ebae --222.64.17.90 (talk) 02:20, 31 July 2009 (UTC)

http://oskicat.berkeley.edu/search/X?SEARCH=t:(Reliability%20Engineering%20%26%20System%20Safety%20)&SORT=D --222.64.17.90 (talk) 03:25, 31 July 2009 (UTC)

BTW, what is the difference between Springer New York and Springer US ??? Are there publisher's identifier around???

http://www.springer.com/advertisers?SGWID=0-110-12-69408-0

http://www.google.com/#hl=en&q=Springer+New+York&aq=f&oq=&aqi=g2&fp=-Pw1cEIpNGU --222.64.17.90 (talk) 03:00, 31 July 2009 (UTC)


 * What is going on here? No one can read your mind, so please detail the above in a more readable manner please. Wizard191 (talk) 14:35, 31 July 2009 (UTC)

Japanese threads
Japan has a metric thread series that is not-quite-ISO, made in accordance with Japanese Industrial Standard (JIS). I encountered them during an engineering job where a U.S. firm had their manufacturing performed by a Japanese company. Standard ISO metric screws and nuts will interchange with JIS metric screws and nuts, but due to tolerance differences, they cannot be torqued to full specification when mixed. True ISO metric screws are more likely to strip the threads out of tapped JIS metric holes. It may be worth pointing out, but not belaboring, in the article.&mdash;QuicksilverT @ 01:23, 19 May 2010 (UTC)

Radius vs. Diameter
In the diagram the Ds denote what would normally be called the radii, not the diameters. Is this correct? (e.g. would an M20 screw have a 20mm diameter, or a 2x20=40mm diameter?) 11:43, 9 August 2010


 * I could be blind, but I don't see a Ds in the diagram. Wizard191 (talk) 13:35, 9 August 2010 (UTC)

Well you wouldn't, he didn't put the s as a subscript because it's a plural, you cock.


 * There are three Dees: Dmin, Dmaj, and DP. In the diagram they denote distance from the thread axis to the trough, the tip, and the middle of the thread, respectively. Now, distances measured from the axis of the thread are radii, not diameters. The diameter is twice the radius.


 * It would be better to denote the three Dees as Rmin, Rmaj, and Rp, and mention somewhere in the text that the Dees are twice the respective Rs shown in the diagram. Then the formulas in the text would also correspond to the diagram. They do not at the moment. 17:03, 12 August 2010 —Preceding unsigned comment added by 131.169.45.220 (talk)


 * If you look closely at the image the diameter dimension lines actually extend past the center line, so it is drawn properly. Moreover, all of the equations in the article refer to the diameters so that means the equations properly relate to the image. Wizard191 (talk) 16:38, 12 August 2010 (UTC)

You should have to look carefully, you cock.

Notation
It would be clearer if the set of equations started with Dmaj = D(nominal diameter) if that is the relation

The text talks of tolerance classes h and g but these are not mentioned in the reference text (ISO 965-1). This uses d and d2 which are not mentioned on this page I think are Dmaj and Dp. some consistency would be useful even where it does not exist in the standards.

The notation M8x1.25 is more commonly used to indicate the length of the bold e.g. M8x60 would be am M8(coarse) bolt 30mm long —Preceding unsigned comment added by 80.229.216.245 (talk) 09:13, 30 April 2011 (UTC)

major diameter is once denoted as D, another time Dmaj: "[...] major diameter D and [...]" vs. "[...] major diameter Dmaj and [...]" - confusing for me.

On top of it, I believe the table is plain wrong: when I measure M4, M6, M8, it has major diameter of 3.6, 5.6, 7.7, according to the table it should be major diameter D=4.0, 6.0, 8.0 81.6.48.229 (talk) 21:43, 24 May 2012 (UTC)

Thread depth
If "thread depth" is $$\frac{5}{8}H$$, as it appears to be from the nearby diagram, then shouldn't this come out as ≈0.541 × P, rather than ≈0.614 × P as stated? — Preceding unsigned comment added by 80.175.14.204 (talk) 15:52, 14 March 2015 (UTC)


 * Hello. I too had this question. I scoured the 'net and couldn't find a good reference for this 0.614 value. However I am assuming it refers to the theoretical thread depth formed by the radii at the top and bottom of the thread crests, as shown in the image below. Again this is just an assumption as it appears to work out in the sketch but I have no idea why it is a specific value of 0.614, although I have seen this number used countless times in other thread references.Dryphi (talk) 15:29, 16 March 2018 (UTC)
 * Thread depth sketch.jpg

Issue - the diagram of the threads has a dimension from the center axis to the farthest distance, a radius, but refers to diameter in the text, and uses the symbol upper case D.
So either the diagram needs to be changed, or the text changed, or the one half needs to be put in some how. — Preceding unsigned comment added by Mtanquary (talk • contribs) 21:48, 11 June 2017 (UTC)

Tap drills
I visited this page hoping to find recommended tap drill sizes for ISO metric threads - it does seem a reasonable thing to include, either in "Preferred sizes" or, more probably, "Wrench sizes", which might become "Wrench and tap sizes". As an electronic, rather than a mechanical, engineer I should prefer to leave the edit to someone more expert, but probably could do it if asked. JMBryant (talk) 17:17, 13 September 2017 (UTC)


 * Good luck. The editors want you (and everyone else) to use those equations and manually derive from first principles that kind of information - presumably because it's not 'encyclopaedic' or some such nonsense. Polymath uk (talk) 15:26, 24 January 2023 (UTC)
 * Perhaps some information could be ported from the Swedish version of this page. It contains a short paragraph on when you want to vary hole diameter from the recommendation and a simple table: https://sv.wikipedia.org/wiki/M-g%C3%A4nga#Borrdiametrar 85.227.199.13 (talk) 19:12, 7 May 2023 (UTC)

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Contradiction - nominal diameter

 * "A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (the ideal maximum thread diameter for external thread or the ideal minimum diameter for internal one) "

Surely an M8 internal thread (nut) should match an M8 external thread (bolt) - using the description above the matching bolt for an M8 bolt would be 8-thread height - eg M7 .. this isn't right ..5.198.10.236 (talk) 16:22, 18 February 2019 (UTC)

afaik the nominal diameter is always the same as the major diamater - eg see table here https://www.newmantools.com/tech/threadm.htm


 * But that works out. The inner thread needs to fit inside the outer thread, so the maximum size of the external (inner) thread should be strictly smaller than the minimum size of the internal (outer) thread, otherwise it wouldn't fit inside. They both have a nominal diameter 8 mm, but they approach the 8 mm from different sides. Neither should surpass that limit from either side. The nominal diameter and major diameter are indeed the same, this doesn't contradict anything about the acceptable tolerance of that diameter. Digital Brains (talk) 17:05, 18 February 2019 (UTC)


 * I happen to be re-reading this, and I spot an oddity in the description. Something is either the ideal dimension, or the minimum dimension. The latter refers to tolerance and thus is inherently speaking about non-ideal situations. I'm removing the word ideal in the text, since it seems misplaced. Yes, the 8 mm for M8 internal thread is the ideal diameter, and it is the minimum diameter. But it is either-or, not both at the same time. Digital Brains (talk) 20:07, 8 April 2019 (UTC)

Historical variant series
I used to own a pamphlet that showed both Japan and France had different diameter x pitch combination for bolts / screws smaller than M6, eg M5x0.9. Below that there were differences between the two. Other than that the German DIN 13 had M5.5x0.9. I still own a thread gauge that includes a blade marked 0.9 located between blades marked 0.8 and 1. These historical oddeties are useful for those who may be restoring, say, old French cars or old Japanese motorcycles etc etc. Back in the late 1960s I remember looking at then new Japanese motorcycles that carried a tag warning "ISO metric threads". Peter Horn User talk 18:36, 25 October 2019 (UTC)
 * Can you find me a table of the original DIN 13 so that I can establish the existance of M5.5x0.9? An authiritive external link will do. Peter Horn User talk 23:38, 26 October 2019 (UTC)
 * Hi Peter, I don't know whether you are looking for an original DIN document where the technical data of M 5,5 0,9 can be found or another document would be helpful for you. I found a PDF file which is called Gewindetabellen and is in German language and there you can find specific technical data on page 519. Have a look via this link http://www.emuge-franken-bg.com/attachments/article/97/15%20Gewindetabellen.pdf Hope this helps. Kind regards -- Ulanwp (talk) 10:47, 27 October 2019 (UTC)
 * Gewinde Gewinge The link does not open, regards. Peter Horn User talk 16:07, 27 October 2019 (UTC)
 * Hi Peter, there must be a problem with your browser than, I guess. I can download and open the file, also the links you have set. They are working well. Webserver is located in Bulgaria. Kind Regards. -- Ulanwp (talk) 16:26, 27 October 2019 (UTC)
 * I can confirm both links work fine! Digital Brains (talk) 17:13, 27 October 2019 (UTC)
 * Mozilla Firefox appeared to be the problem. Google Chrome enabled me to open this informative link right away. Peter Horn User talk 01:26, 28 October 2019 (UTC)
 * I'm using Firefox as well and it works. There must be another problem with your computer/browser. -- Ulanwp (talk) 09:04, 28 October 2019 (UTC)
 * The above external links do not mention M5.5X0.9 Peter Horn User talk 22:01, 25 April 2021 (UTC)
 * Add M5.5 x 0.9 Peter Horn User talk 21:45, 25 April 2021 (UTC)
 * Gewindetabellen 15.3 page 519

15.3 Metrisches DIN-Gewinde (veraltet) Auszug aus DIN 13 (ungültig) und DIN 13-1 (ungültig) Außengewinde Ohne speziellen Hinweis fertigt EMUGE die Abmessungen mit Toleranzen nach DIN ISO 965-1! ❚ ❙ ❘ ➤ Gewindetabellen 15 519

Außengewinde

1,7 0,35 1,473 1,518 0,045 0,010 1,256 1,346 0,090 1,473 1,544 0,071 0,010 1,256 1,346 0,090 2,3 0,4 2,040 2,090 0,050 0,015 1,795 1,920 0,125 2,040 2,120 0,080 0,015 1,795 1,920 0,125 2,6 0,45 2,308 2,358 0,050 0,020 2,036 2,176 0,140 2,308 2,388 0,080 0,020 2,036 2,176 0,140 5,5 0,9 4,915 4,978 0,063 0,026 4,357 4,581 0,224 4,915 5,015 0,100 0,026 4,357 4,581 0,224

1,7 0,35 1,629 1,700 0,071 1,428 1,473 0,045 1,629 1,700 0,071 1,402 1,473 0,071 1,246 2,3 0,4 2,200 2,300 0,100 1,990 2,040 0,050 2,200 2,300 0,100 1,960 2,040 0,080 1,780 2,6 0,45 2,488 2,600 0,112 2,258 2,308 0,050 2,488 2,600 0,112 2,228 2,308 0,080 2,016 5,5 0,9 5,320 5,500 0,180 4,852 4,915 0,063 5,320 5,500 0,180 4,815 4,915 0,100 4,331

Failed verification
I removed the paragraph below due to the failed verification tag. It also lacks clarity.

"Using the multiplication sign could cause misunderstanding. Therefore the pitch is always indicated with two decimals. (e.g., M10×1.25×30). As a length of 1,00 mm obviously is not valid as well as a pitch of 16 mm on an M8 bolt would not be valid (M8×16), using the multiplication sign is unambiguous. Refer to paragraph 12.2 of ISO 965-1:2013 for this."

--Srleffler (talk) 16:59, 16 April 2022 (UTC)

This article is becoming less and less useful as technical people overwhelm it with textbook-speak
Came here to find the major and minor diameters for M3. Nope - not included. I'm sure that the article very faithfully follows all the wikipedia standards and the ISO standard that specifies the thread. This is not a good reason to remove useful information, however, AT ALL. Polymath uk (talk) 15:25, 24 January 2023 (UTC)


 * Was this information ever in the article? I don't see it, in which case ranting about it being removed seems inappropriate.  ISO 68-1 doesn't define major and minor diameters (although the major diameter is fairly obvious), only the shape of threads for any particular pitch.  For a particular major (ie. nominal) diameter and pitch (as defined, for example in ISO 261), the minor diameter can be calculated:
 * $$\begin{align}D_\text{min} &= D_\text{maj} - 2\cdot\frac58\cdot H = D_\text{maj} - \frac{ 5 {\sqrt 3}}{8}\cdot P \approx D_\text{maj} - 1.082532 \cdot P \\[3pt]\end{align}$$
 * A table could be included, or just extra columns added to the existing table in the preferred sizes section. A good engineering reference (although no engineer should be using Wikipedia as a reference!) should include mention of tolerances, although expanding the table to show the various defined tolerance ranges would make it very unwieldy.  Lithopsian (talk) Lithopsian (talk) 17:17, 24 January 2023 (UTC)

Which came first?
An important part of this article matches word-for-word some content which is claimed as copyright at Engineer's Edge. I can't figure out which is copied from which. It would seem odd that text would be copied from Wikipedia and then claimed as copyright. The Wikipedia text evolved somewhat between about 2008 and 2010. Lithopsian (talk) 18:12, 24 January 2023 (UTC)