Allen key screw heads

[SillyOldDufferModerator @sillyoldduffer]

Posted by Vic on 14/08/2016 18:54:15:

I must admit that some imperial nuts and bolts look better than metric ones. It seems to be the ratio between thread diameter and nut/head size. Anyone know why metric seem to have larger heads/nuts?

I hope someone who knows can tell us. My guess: general purpose metric fasteners have head and nut dimensions specified to reduce the risk that they'll get chewed up when used in average applications.

Dave

[Peter KroghParticipant @peterkrogh76576]

Polly Engineering have what look to be hex head screws with well proportioned heads. Mostly metric.

Pete

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 14/08/2016 20:40:24:

I hope someone who knows can tell us.

.

I did

[JasonBModerator @jasonb]

Peter, they are the fixings I mentioned earler on in the thread, actually come from GHW in Germany

Compare standard M4 & M3 with the GHW offerings

They are very nicely made and if anything a little tall on certain sizes. I was using some M1.6 ones today which look good having a 2.5mm A/F Also got a nice little nut driver from GHW for them wich is 3.5mm OD so fits into tight spaces, Just what I needed for the Jowitt Jnr's bearing caps.

 

I would be interested to know how the metric AF sizes were worked out as there seems no logic to it. Most threads have the hex at so many times D but metric seem to vary. M6 with 13mm hex is 2.17xD but something like M10 at 17mm hex only 1.7D?

Edited By JasonB on 14/08/2016 21:09:15

[Anonymous]

Posted by JasonB on 14/08/2016 21:08:25:

M6 with 13mm hex is 2.17xD but something like M10 at 17mm hex only 1.7D?

Machinery's Handbook says that a M6 nut is 10mm AF max, which is what my commercial nuts measure? Sure you're not one line out; M8 is 13mm AF.

Andrew

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 14/08/2016 20:56:23:

Posted by SillyOldDuffer on 14/08/2016 20:40:24:

I hope someone who knows can tell us.

.

I did

Oops, sorry! I over-focussed on the IKEA joke.

But do you know why metric preferred clearance holes are bigger?

Ta,

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Dave,

My understanding is that the preferred clearance holes are larger to allow more convenient manufacture and assembly of mass-market items.

As for the IKEA joke: Many a true word is spoken in jest. … It was 'shorthand' for a more complicated description.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Andrew Johnston on 14/08/2016 21:21:48:

Posted by JasonB on 14/08/2016 21:08:25:

M6 with 13mm hex is 2.17xD but something like M10 at 17mm hex only 1.7D?

Machinery's Handbook says that a M6 nut is 10mm AF max, which is what my commercial nuts measure? Sure you're not one line out; M8 is 13mm AF.

Andrew

.

Interesting page here might help explain some of the discrepancies.

http://www.sat.dundee.ac.uk/psc/spanner_jaw.html

MichaelG.

[Peter KroghParticipant @peterkrogh76576]

Jason, thanks for the info on the source of those fasteners. The Polly page is the only place I've seen them. This has been a stressful week, which is probably why I 'spaced' your references and links…..

Pete

 

Edited By Peter Krogh on 15/08/2016 00:12:56

[JasonBModerator @jasonb]

Thanks Andrew, got my M8 and M6 mixed up.

Peter, if you use one of the online translators there is a lot more size info on the GHW site than Polly's, works out a bit cheaper too.

[Gordon WParticipant @gordonw]

I've just been working on my chinese tractor- M8 nuts and bolts, 12, 13 & 14 mm A/F.. And lots off clearance in the holes, but it all works.

[VicParticipant @vic]

Those GHW nuts look very nice Jason. I suppose it proves not all metric nuts are equal. I wonder if older imperial nuts were always designed to be used with washers to spread the load?

[Peter KroghParticipant @peterkrogh76576]

Jason, I've bookmarked the GHW site. My German is really weak but they seem to have some good stuff there. I'll go back later, with translator in hand….

Finding small fasteners with proper proportions is a real problem, especially Imperial sizes. Those metric fasteners at GHW are nice enough I just might have to start using metric. For model fasteners anyway….

I do use both systems but metric when the job, usually a repair, demands it.

Pete

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