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4.8 bolt
graememk - 13/5/08 at 03:05 PM

how strong is a 4.8 10mm bolt please

tegwin - 13/5/08 at 03:09 PM

I caclulate it to be 45000N.....But that figure doesnt seeem right...

coozer - 13/5/08 at 03:09 PM

400N but found this as well.. good luck!


In accordance with BS 3692:2001

The designation system allows the determination of the ultimate and yield/proof strength of the bolt. The designation system is based on two numbers e.g 8.8 . The first number is the tensile strength of the bolt material (N2 )/100. The second number is = 1/100.(the ratio of the Proof (or Yield ) stress and the Tensile strength expressed as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100

The tensile and proof strength of the steel for a 4.6 bolt is therefore calculated as follows

Tensile strength (Rm) = 4.100 N/mm2 = 400 N/mm2 .... Proof strength (R0,2) = 0,6*400 * 100 /100 = 240 N/mm2

SO... 4.8 = 320N

[Edited on 13/5/08 by coozer]

Mr Whippy - 13/5/08 at 03:15 PM

quote:
Originally posted by tegwin
I caclulate it to be 45000N.....But that figure doesnt seeem right...


hmm please don't say you design aeroplanes...

MikeCapon - 13/5/08 at 03:30 PM

Hi. It's about half the strength of an 8.8.

See here

matt_claydon - 13/5/08 at 03:32 PM

The first number is the ultimate tensile strength, in hundreds of Newtons per mm^2. The second number is the percentage (divided by 10) of the ultimate strength at which the material will yield (permanently deform).

e.g. A 4.8 bolt has an UTS of 400 N/mm^2 and a yield stress of 80% of this - 320 N/mm^2.

To actually work out the strength of the bolt you obviously need to multiply this figure by the cross-sectional area of the bolt in mm^2.

For M10 the minor diameter is about 8.5mm so the area is pi * (8.5/2) * (8.5/2) = 57mm^2 so the yield strength is 57*320 = 18000 N or about 1.8 tonnes.

[Edited on 13/5/08 by matt_claydon]

zzr1100rick2 - 13/5/08 at 03:37 PM

About as strong as a hard cheese

stevec - 13/5/08 at 04:36 PM

You have bought something Chinese I think?
They use crappy bolts like that.
Steve.

balidey - 13/5/08 at 05:12 PM

quote:
Originally posted by stevec
You have bought something Chinese I think?
They use crappy bolts like that.
Steve.


No, the Chinese make bolts like that, but stamp them 10.9
The sooner the UK gets over the facination of buying cheap sh!te from Asia the better.

iank - 13/5/08 at 05:30 PM

Throw it in the bin and use an 8.8 or better.
Reusing old knackered weak bolts is a mugs game.

Wadders - 13/5/08 at 05:35 PM

Strangely enough a lot of structural steel is held together with 4.8 bolts.

Al.







Originally posted by zzr1100rick2
About as strong as a hard cheese

mcerd1 - 13/5/08 at 05:38 PM

quote:
Originally posted by iank
Throw it in the bin and use an 8.8 or better.
Reusing old knackered weak bolts is a mugs game.


^^^^ what he said

some structural steelwork is done with 4.6 and 4.8 bolts - but allot of it is done with 8.8 (all the stuff we make uses 8.8)




I know that ford use a minimum of 8.8 on the sierra's and cossies with critical bolts like the brakes/ driveshafts 10.9 or 12.9




its also worth mentioning that all the above strengths are tensile only - bolts are weaker in shear

in a car alot of bolts are likley to be subjected to impact and other dynamic loads (which are much higher than static loads)
most structural steelwork won't suffer the same kind of impact loads - at least you'd hope not




all the following is from BS 5950:2000 (the main uk structural steel standard)

nominal tension capacity = 0.8 * tension strength * tensile stress area

M12, 4.6 = 0.8 * 240 * 84.3 = 16.2kN
M12, 8.8 = 0.8 * 560 * 84.3 = 37.8kN
M12, 10.9 = 0.8 * 700 * 84.3 = 47.2kN

single shear capacity = shear strength * shear area (normally the same as tensile area)

M12, 4.6 = 160 * 84.3 = 13.4kN
M12, 8.8 = 375 * 84.3 = 31.6kN
M12, 10.9 = 400 * 84.3 = 33.7kN

also bearing strength = bolt diamiter * thinkness of the part * bearing strength

bearing strengths:
4.6 = 260
8.8 = 1000
10.9 = 1300

[btw - I've quoted values for M12 because its the smallest in my book, and as an engineer I'm too lazy to work out the M10 values ]


[Edited on 13/5/08 by mcerd1]

nstrug - 13/5/08 at 07:12 PM

And remember that the stronger the bolt, the higher it must be torqued: http://www.cncexpo.com/MetricBoltTorqueNm.aspx

Nick

Wadders - 13/5/08 at 08:00 PM

Funny things bolts, my mate fitted the front discs to his 750cc bike using stainless slot headed machine screws, cos they were shiny and he had some in a drawer.

Despite all the warnings of impending doom and disaster, they proved reliable for at least 40k miles to my knowledge.

Maybe we all worry a bit too much

Personally never use anything below an 8.8 for anything my life depends on.

Al