Replacing unf bolts with metric equivalents

AlbertDefender90 · Nov 24, 2014

Hi all,

I'm currently having a nightmare with the fine threaded bolts on my rebuild especially the A frame ball joint bracket mounting bolts where the nuts keep stripping before they're anywhere near the correct torque (I'm getting up to 140 Nm and they should be 176).

Anyway, do you think it's safe using the equivalent sized high tensile metric bolts instead as through previous experience they generally hold up to higher torques better?

Thanks

Albert

jamesmartin · Nov 24, 2014

AlbertDefender90 said:
Hi all,

I'm currently having a nightmare with the fine threaded bolts on my rebuild especially the A frame ball joint bracket mounting bolts where the nuts keep stripping before they're anywhere near the correct torque (I'm getting up to 140 Nm and they should be 176).

Anyway, do you think it's safe using the equivalent sized high tensile metric bolts instead as through previous experience they generally hold up to higher torques better?

Thanks

Albert

fine threads (unf)dont need to be torqued up so high as std metric and thats too high anyhow for a 7/16 or 12mm bolt

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
fine threads (unf)dont need to be torqued up so high as std metric and thats too high anyhow for a 7/16 or 12mm bolt

Well that's the setting I have in my manual and what my local dealer gave me

jamesmartin · Nov 24, 2014

for the bolts that secure a frame arms to fulcrum bracket ?

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
fine threads (unf)dont need to be torqued up so high as std metric and thats too high anyhow for a 7/16 or 12mm bolt

I don't suppose you know the correct setting for it at all?

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
for the bolts that secure a frame arms to fulcrum bracket ?

Yeah, give us a minute and I'll recheck

jamesmartin · Nov 24, 2014

80 lbsft or 90 nm would be nearer

The Mad Hat Man · Nov 24, 2014

top link to mounting bracket - 176Nm
upper joint to levelling unit - 34Nm
Lower joint to levelling unit - 34Nm
Bottom link to axle - 176Nm
Bottom link to chassis - 176Nm
Top link bracket to rear cross member - 47Nm
levelling unit to cross member - 47Nm

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
80 lbsft or 90 nm would be nearer

Wow, that's a lot lower, no wonder I'm having issues. Anyway here's the info from my manual:

Relevant torques at the bottom of the image.

The Mad Hat Man · Nov 24, 2014

#^^^^ looks the same as mine

AlbertDefender90 · Nov 24, 2014

The Mad Hat Man said:
#^^^^ looks the same as mine

So where am I going wrong, it's driving me mad now 😖

jamesmartin · Nov 24, 2014

id say theres a mistake 176 nm is too tight for a 12 mm bolt 12,9 or not,less for a unf fine thread as there is greater leverage with a fine thread

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
id say theres a mistake 176 nm is too tight for a 12 mm bolt 12,9 or not,less for a unf fine thread as there is greater leverage with a fine thread

So would I be safe with an m12 10.9 wound up to around 120Nm then?

jamesmartin · Nov 24, 2014

you can try it bolt would certainly be tight enough ,bolts are a dowel fit in arms and fulcrum

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
you can try it bolt would certainly be tight enough ,bolts are a dowel fit in arms and fulcrum

Dowel fit?

jamesmartin · Nov 24, 2014

a very good fit through holes so theres no movement for shearing ,a looser fit would require greater clamping pressure

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
a very good fit through holes so theres no movement for shearing ,a looser fit would require greater clamping pressure

Mine are a pretty crap fit to be. Honest, tightened it up in my vice and it was way out of line

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
a very good fit through holes so theres no movement for shearing ,a looser fit would require greater clamping pressure

Mine aren't the best fit to be honest, I'll try a regulate m12 bolt before I buy anything special

jamesmartin · Nov 24, 2014

just buy the proper bolts ,the shank is a specific length

AlbertDefender90 · Nov 24, 2014

jamesmartin said:
just buy the proper bolts ,the shank is a specific length

Yeah I suppose, it just bugs me not knowing if I'm doing it right

Replacing unf bolts with metric equivalents

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