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1Back to top Go down   Measurement of fasteners/bolts Empty Measurement of fasteners/bolts on Fri Aug 23, 2013 1:55 pm

jjefferies

jjefferies
Silver member
Silver member
Terribly minor question but when bolts/fasteners are called out in parts such as
"FILLISTER-HEAD SCREW - M8X45"
Am I correct that this 8mm (diameter) by 45 millimeters long and the length measurement includes the head as well as the shank? Is there a special designation for very short headed bolts? And is there an assumption of the quality such as grade 8?

And is there a major bias for the Fillister-head (allen socket) type bolt over the more prosaic hex headed bolt on BMW's. And why I'm noticing this sort of thing this morning is most likely due to lack of sleep. But I also note that the 7mm bolts used to hold the clutch housing together are called out as "screw" in Max-BMW's micro-fiche rather than giving their measurement.

    

2Back to top Go down   Measurement of fasteners/bolts Empty Re: Measurement of fasteners/bolts on Fri Aug 23, 2013 6:34 pm

xpc316e

xpc316e
Gold member
Gold member
An M8 bolt has a diameter of 8mm and, unless it has a countersunk head, its length does not include the head.

Here is a really useful chart that explains much of the mystery:

http://www.boltdepot.com/fastener-information/Printable-Tools/Fastener-Basics.pdf


__________________________________________________
VIN 0191428, 1991 K100LT, formerly owned by Lancashire Constabulary. This old warhorse is now 'out to grass' and living in retirement in Suffolk, where it will be showered with appropriate love and care.

VIN 6459609, 1992 K1100LT, another ex-Police machine, even though she now looks like she is a former fire engine.
    

3Back to top Go down   Measurement of fasteners/bolts Empty Re: Measurement of fasteners/bolts on Fri Aug 23, 2013 11:05 pm

jjefferies

jjefferies
Silver member
Silver member
Thanks, that was certainly an interesting quick read. But it does leave me with a basic question. The filister/allen head bolts I used to bolt the tranny to the engine were micro-fiche listed as M8X45. But when I go through my pile, and it's large, of bolts the nearest I find to 45mm long is if you measure the head as well as the shank. Which is what was puzzling me. 

Oh, well it's back together and I suspect there are enough mm in there to hold anything.

    

4Back to top Go down   Measurement of fasteners/bolts Empty Re: Measurement of fasteners/bolts on Fri Aug 23, 2013 11:09 pm

robmack

robmack
Life time member
Life time member
M8 would represent the course thread pitch.  For fine and extra fine pitch, the pitch designation will also be included:

Wikipedia wrote:A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (Dmaj in the diagram above) and the pitch P, both expressed in millimetres and separated by the multiplication sign, × (e.g., M8×1.25). If the pitch is the normally used "coarse" pitch listed in ISO 261 or ISO 262, it can be omitted (e.g., M8).
Thus M8 x 1.25 x 45 would be an M8 bolt of 45mm shank length with a 1.25mm pitch thread.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

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