ISO / DIN standard for screw head geometry

Hi DaveD - I used to work for a fastener manufacturer in the 90's as a mechanical engineer. At the time, the German DIN standards organization published a set (we had 5-6 books if I recall properly) of reference books (the book covers were light-blue in color) that defined the head geometry dimensions you might be looking for. Our DIN-books were kept by the folks who ran our quality control department. You may want to check with the quality folks you're working with to see about getting access to these reference books (they could be in digital format now, of course), or contact the DIN organization in Germany directly. These standards are pretty valuable to the DIN organization, so I don't think you'll have too much luck finding them for free on the web. If you haven't looked already, other references (for ISO and other standards) to check for (US point of view here) might include the "Machinery's Handbook" and the IFI Handbook. Good luck! - april05

1- as far as I know TORX is a proprietary profile not a DIN standard.

For DIN printed norms you should contact the editor in germany or order via Amazon the editor is the "Beuth Verlag".

Machinery Handbook

I believe the profile would determine the respective geometry to the extent the hex head geometry would be essentially similar for that of TORX

Thanks for the comments. I'm not much closer to finding the answer.

My problem is that there appears to be two sizes of (90 degree)countersunk head geometry possible for an M4 screw. One with a theoretical sharp maximum of 8.96mm the other 8.40mm. The larger one is found mainly on hex socket recess screws the smaller one mainly for cross, slotted and hex-lobe('Torx') recess screws. I need to find out a suitable standard for the smaller diameter countersunk head geometry.

What I don't want to do is buy a standard and find out that it's the wrong one!

The info I have shows DIN7991 & BS4168 for hex socket c'sk screws (ø8.96), DIN965 for pozi c'sk & torx.

Thanks Nigh

I'm getting nearer. BS4183 I believe is obsolete. DIN ISO 965 is in 5 parts and appears to be about the screw thread rather than the head geometry.

However your input has led me down another avenue and I think that ISO 7721 may be the one I'm looking for.

Thanks Milo,

I've been surprised that it's so difficult to find a suitable standard. Countersunk head details for screws get fairly critical when using them in thin sheet metal parts. I have to ensure that the screw head does not protrude into a paper path (as you can imagine, for the edge of a sheet of paper, any protrusion is a potential catch point) At the same time there is not much room to manouevre with the size of the countersink detail in the sheet metal.

Screw suppliers quote ISO standards for screw threads (typically ISO 965) but, while I can find information on screw head geometry in some supplier details, this info does not reference to any standard. Consequently when there is a problem raised from the quality dept about a countersunk screw head that is too small/big I have not been able to point to a specific standard only to a page from a supplier catalogue. Maybe I'm pedantic but as an engineer I like to be able to specify adequately for the application and sometimes that has to be with reference to a recognised standard.

So far my research on the web suggests that 'ISO 7721:1983 Countersunk head screws - head configuration and gauging' may be the one or possibly 'ISO 4759-1:1978 Tolerances for fasteners - Part 1: Bolts, screws and nuts with thread diameters between 1.6 and 150mm and product grades A, B and C.'

What I need is a web site that will let me read a standard before buying it - a virtual standard reference library.

DaveD

Not web based but some places hold full sets of BS & ISO standards. Try your local reference library, university reference libraries or, if you are a member of a professional body, their own library. Ask if they have an inter library lending scheme, some are willing to lend companies books or standards by post.

Send me a real non cr4 email by clicking on my name and sending me a private message, and I will have a copy of IFI 535 metric socket countersunk head cap screws scanned and sent to you. ithas the 8.96 theo. sharp value youmentioned in a table for M4, I expect this standard will be of use to you. I think that this spec was being copnsidered by ASME B18 And was supposed to be designated ANSI/ASME B18.3.5 But I haven't followed it. Send your email, I'm getting it scanned as I typoe.

milo

We are also looking for a copy of this spec (IFI 535 metric socket countersunk head cap screws) and have not been successful at finding one up to now. If we could possibly get a copy from you, that would be great, please let me know.