torque for 3/8" cap screws in 80x hubs

[ANDREWGQ 351]

From the Unbrako cataloge
M8 12.9's recomended seating torque 39Nm
3/8 12.9's recomended seating torque 64Nm
M10 12.9's recomended seating torque 77Nm

SHCS's would not normally use any type of washer under the head.
Use a loctite not one to strong though, you need to get them out easily. Loctite acts as a lubricant and reduces thread friction allowing more accurate torques, it also fills the thread area reducing the space for the bolt to bend and move around in.

Bolts only break in shearing, tension or bending fatigue.

Without the dowels the bolts do the locating and the flange can rotate slightly back and forward, this increases shearing posibility and creates bending fetigue.

If the bolts are not tightened to the correct torque they will fail under bending fatigue

If bolts are over tightened beyond their yeild point then the clamping force will actually reduce allows bending fatigue to occure

[rockcrawler31]

From the Unbrako cataloge
M8 12.9's recomended seating torque 39Nm
3/8 12.9's recomended seating torque 64Nm
M10 12.9's recomended seating torque 77Nm

SHCS's would not normally use any type of washer under the head.
Use a loctite not one to strong though, you need to get them out easily. Loctite acts as a lubricant and reduces thread friction allowing more accurate torques, it also fills the thread area reducing the space for the bolt to bend and move around in.

Bolts only break in shearing, tension or bending fatigue.

Without the dowels the bolts do the locating and the flange can rotate slightly back and forward, this increases shearing posibility and creates bending fetigue..

If the bolts are not tightened to the correct torque they will fail under bending fatigue

If bolts are over tightened beyond their yeild point then the clamping force will actually reduce allows bending fatigue to occure

awesome tech dude

[rockcrawler31]

Would be nice to get SHCS with a short shank rather than dragging on the thread but suppose it doesn't really hurt the cones.

[

Just buy longer bolts with the shank length you want then cut the end off to get the overall length right.

Sam

This is what i have done. I have about 13mm of shank and 50mm of thread which i will just trim down to the right length.

[rockcrawler31]

What's all the crap about extra dowels, surely those 2 (or 4) 8mm dowels are not designed as drive pins but as locators.

I am led to believe that it is the dowels that do a fair proportion of the work in transferring torque to the hub. I have match drilled the axles to the hubs, pulling out the original dowels and redrilling for larger ones, then drilling out the threaded puller holes for the same

[KiwiBacon]

If your bolts do their job, then the dowels and bolt threads take no shear force.
It's only when the bolts get loose and the flange can shif that shear force becomes a problem.

[bazzle]

m8 is nearly same as 5/16 not 3/8.

Bazzle

[KiwiBacon]

Without the dowels the bolts do the locating and the flange can rotate slightly back and forward, this increases shearing posibility and creates bending fetigue.

If the bolts are not tightened to the correct torque they will fail under bending fatigue

If bolts are over tightened beyond their yeild point then the clamping force will actually reduce allows bending fatigue to occure

The above points are incorrect.

Regardless of dowels, a bolted join carries shear load via friction between the two faces. If the flange can rotate or move even slightly then the joint has failed and will soon come apart.

A bolt can only suffer bending fatigue if the joint is loose. Overtorque won't cause bending fatigue.
If bolts are tightened beyond yield the clamping force does not reduce until the bolt is virtually broken in two.

[fester2au]

Would be nice to get SHCS with a short shank rather than dragging on the thread but suppose it doesn't really hurt the cones.

[

Just buy longer bolts with the shank length you want then cut the end off to get the overall length right.

Sam

Do it all the time but sometimes not easy to get the right combo and with only a couple of bolt places in town it's not easy to find differing stock suppliers with different lengths. We get stainless bolts in bulk from a particular supplier (direct from out of town) and sometime they can;t even tell us what shank if any a certain size bolt has, depends on who their main importers get their stock off at any given time.

[hulsty]

M8 x 45 grade 12 SHCS + 1 x m8 hi-tensile washer + original cone + original spring washer....

what is the thread pitch? I'm going to get rid of my studs and go a SHCS set front and rear. Is it possible to get them with a shank or only threaded?

Might go the route of to long ones and cut them down to get the shank if I have to