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Military Spec Fasteners


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Would anyone happen to know a source for Military specification nuts and bolts? Most of the mil spec hex head bolts seem to be smaller across the flats of the head for its given size to the off the shelf items. Some instances conventional nuts and bolts are fine but others require the smaller head sizes for clearance when in position. Done the usual internet searching with little luck.

 

Chris.

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Would anyone happen to know a source for Military specification nuts and bolts? Most of the mil spec hex head bolts seem to be smaller across the flats of the head for its given size to the off the shelf items. Some instances conventional nuts and bolts are fine but others require the smaller head sizes for clearance when in position. Done the usual internet searching with little luck.

 

Chris.

 

Hi Chris,

It depends on what thread these fasteners are. I have worked on military vehicles for over 40 years and do not recall any Military spec fasteners with smaller heads. BSF/BSW generally have the largest head size in relation to thread diameter, then I guess Metric are next down and UNF/UNC are possibly the smallest head size in relation to thread diameter. What vehicle or equipment is this related too?

 

regards, Richard

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Hi Richard,

 

I have M12 set screws with 18mm A/F heads and M10 with 16mm A/F. Conventionally these should be 19mm and 17mm A/F accordingly. These are used on certain chassis points on my RB44 and are the original ones as fitted. I'm guessing these were specials for the application.

 

Cheers

 

Chris.

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I have some very fat COSAs Section G1-Part 1 Metric fasteners, but the head to thread size is not addressed. I thought there might be some mention in Def Stan 07-104 - "Definitive Referencing of British Standard (General series) Threaded Fasteners" Part No: 1 - "Screws, Machine, Metric - BS4183" I have just checked their site but I see "This Defence Standard was withdrawn on 08/11/1981"

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Hi Richard,

 

I have M12 set screws with 18mm A/F heads and M10 with 16mm A/F. Conventionally these should be 19mm and 17mm A/F accordingly. These are used on certain chassis points on my RB44 and are the original ones as fitted. I'm guessing these were specials for the application.

 

Cheers

 

Chris.

 

Hi Chris,

I don't think these bolts could be termed 'military specific'. At one time I worked on a lot of equipment (not military) with UNF fasteners. I think it was 7/16" UNF bolts that had 5/8" A/F heads, but nuts were 11/16" A/F, then you would come across same bolts with 11/16" A/F heads. Going to Metric, some 10 mm bolts have 11mm A/F heads rather than the normal 10mm.

The bolts you mention on the RB44 chassis, could have smaller heads due to restrictions in getting a socket or spanner on them maybe.

 

cheers Richard

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UNF/C Socket head cap screws may have different head diameters depending on whether they were made to 1936 spec or 1960 spec, the socket wrench size is also different, even though the thread size is the same.

 

Diana

 

 

 

Would anyone happen to know a source for Military specification nuts and bolts? Most of the mil spec hex head bolts seem to be smaller across the flats of the head for its given size to the off the shelf items. Some instances conventional nuts and bolts are fine but others require the smaller head sizes for clearance when in position. Done the usual internet searching with little luck.

 

Chris.

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Metric 'flange-bolts' as a rule have a hex. size smaller than a standard bolt or set , hence this is why on cars you will often find the preferred 13 , 17 & 19 spanner sizes not so often used - you will find you are using 18mm 16mm 15mm 14mm & 12mm

 

IIRC - you will often find car makers bolts on suspensions etc. these often have a fine metric thread and uncommon lengths (specials) and the spanner sizes are also smaller , the alternatives 18, 16, 15, 14 & 12. In a few cases they are not flanged nuts & bolts !

 

Recently I changed anti-sway bar links on a Focus and a Peugeot 207 , the links were similar sizes IIRC the threads were same dia. & because the hex. nuts were serrated grip flange nuts - ISTR using all the five spanners and not 13, 17, 19.

 

Coppered exhaust manifold nuts are also often flange nuts - the common spanners used are 12mm & 14mm - never 13mm ,,

Edited by ruxy
spelin
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Try Ray-tek on ebay.

 

Diana

 

 

Would anyone happen to know a source for Military specification nuts and bolts? Most of the mil spec hex head bolts seem to be smaller across the flats of the head for its given size to the off the shelf items. Some instances conventional nuts and bolts are fine but others require the smaller head sizes for clearance when in position. Done the usual internet searching with little luck.

 

Chris.

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