front brake caliper bolts (granada)
Discussion
tallbloke said:
They will probably have been marked with blue paint on the end, denoting high tensile material. Best to get the right replacement if you can. The numbers stamped on the head should help.
The blue paint is usually loctite or similar. Agree that they are high tensile bolts but even so nothing special about them.
jchase said:
I would guess the loctite is more important than the tensile strength, as even pop rivets take 2kN in shear.
-Jim
Hmmm. I think the reason for the choice of material has more to do with its resistance to plastic deformation than shear strength. These bolts have to be tightened to fairly high torques several times over their designed life-span because you wouldn't want them coming loose in service. Part of what keeps bolts tight is their ability to maintain a grip through friction because they deform elasticly rather than plasticly. Relying on loctite to hold a fixing which can get very hot is not a good plan IMO.
Hi Tall bloke,
Intereting comment about the loctite - I recently did a brake pad job on a friends Ford Ka - and the calipers have to removed for this operation (d'oh). The bolts were very thin, like M8 or so - and they were secured with loctite blue. (all my Alfas had M10 bolts and no threadlock). Loctite also do other fixants, some permanent, unlike the blue which is designed to be undone eventually.
I was under the impression that all plastic deformation was ultimately due to internal shear ? I could be wrong , but that is what I seem to recall.
Surely FORD must have these bolts in stock, I bet they use them in other applications - don't Morgan still make cars with the cortina front end?
-Jim
Intereting comment about the loctite - I recently did a brake pad job on a friends Ford Ka - and the calipers have to removed for this operation (d'oh). The bolts were very thin, like M8 or so - and they were secured with loctite blue. (all my Alfas had M10 bolts and no threadlock). Loctite also do other fixants, some permanent, unlike the blue which is designed to be undone eventually.
I was under the impression that all plastic deformation was ultimately due to internal shear ? I could be wrong , but that is what I seem to recall.
Surely FORD must have these bolts in stock, I bet they use them in other applications - don't Morgan still make cars with the cortina front end?
-Jim
Any local stockist should be able to supply you with these. If i remeber correctly they are just an M12 grade 8.8 bolt. Possible that they may be UNF, cna't remeber off the top of my head. Either way as SHpub said earlier, nothing special.
The number on the top of the bolt head denote the bolt capacities i.e grade 8.8 = 31.6kN shear capacity and 37.93kN tensile capacity. This includes safety factors.
If there are no numbers but a seiries of radial raised notches in the head this indicates that they are an imperial thread, most probably UNF or UNC (F=fine, C=coarse) thread. different arrangements and numbers indicates the bolt capacities. This link gives a good idea of the range www.engineersedge.com/hex_bolt_identification.htm
I would be inclined to do as Tallbloke suggested and pop down the local scrappies. When i've been down for odds and sods like this they often haven't even charged.
Hope this helps.
Mick
The number on the top of the bolt head denote the bolt capacities i.e grade 8.8 = 31.6kN shear capacity and 37.93kN tensile capacity. This includes safety factors.
If there are no numbers but a seiries of radial raised notches in the head this indicates that they are an imperial thread, most probably UNF or UNC (F=fine, C=coarse) thread. different arrangements and numbers indicates the bolt capacities. This link gives a good idea of the range www.engineersedge.com/hex_bolt_identification.htm
I would be inclined to do as Tallbloke suggested and pop down the local scrappies. When i've been down for odds and sods like this they often haven't even charged.
Hope this helps.
Mick
colinrees said:
Thanks for the info, i am sure i will find something. To be honest i had assumed that these were UNC threads, but perhaps they are metric. Is there an easy way for a non engineer to tell ?
it has 8.8 stamped on the end but not much else.
Thanks for the help and sorry for being slow
M12 x 1.5 if I remember correctly. Esay way to tell is to try an M12 nut on one.
jchase said:
Hi Tall bloke,
Intereting comment about the loctite - I recently did a brake pad job on a friends Ford Ka - and the calipers have to removed for this operation (d'oh). The bolts were very thin, like M8 or so - and they were secured with loctite blue.
Hi Jim
I don't doubt they were secured with loctite, but I'd be surprised if they were mild steel bolts. M8 seems pretty thin all the same, though I'm sure Ford will have done their homework.
jchase said:
I was under the impression that all plastic deformation was ultimately due to internal shear ? I could be wrong , but that is what I seem to recall.
That's right, it's just that higher tensile material is less prone to it than mild steel. This means there will be less chance of the bolt stretching under tension, thus reducing the pressure maintaining the friction which keeps the bolt secure.
colinrees said:
Thanks for the info, i am sure i will find something. To be honest i had assumed that these were UNC threads, but perhaps they are metric. Is there an easy way for a non engineer to tell ?
it has 8.8 stamped on the end but not much else.
If it's got 8.8 stamped it is definitely Metric, as said before M12 x 1.5 standard metric thread. Should be common and easy to find. Any local engineering works or bolt suppliers should be able to sort you out.
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