switching from sae to metric wheel studs

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oldsmobile joe

Royal Smart Person
Nov 12, 2015
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i want to switch my rear axle wheel studs from 7/16 to 12mm. the knurle of the metric stud is larger than the 7/16 stud. if the metric dimension is 12.7mm (.501"), what dimension do i need to drill the axle?
 

pagrunt

Geezer
Sep 14, 2014
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Might be easier to just swap out to newer axles that have metric studs. I'd offer the set from my old rear end but it's still on the old frame to move it.
 

455'ed80Regal

Master Mechanic
Nov 3, 2010
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What he said^^^. Or go screw in studs.
 

pontiacgp

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Mar 31, 2006
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for a wheel stud you'll need around .005" interference fit and no less than .002" A 12.5 mm drill bit will open the hole to .492" which will be good. You can get a more accurate hole with a reamer but they get kind of expensive.
 
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clean8485

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Dec 18, 2005
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I just performed a similiar conversion. I ended up pulling the axle shafts, and taking them to a machine shop. They pressed out the old studs, then measured the knurl on the new metric studs, and reamed out the stud holes in the axle flanges to allow the metric studs to fit with the proper interferance, then pressed the new metric studs in. Not the cheapest or easiest way to go, but definitely the best chance of getting the job done correctly.
 
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pontiacgp

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before you open the holes are have a shop do it make sure the axle is good. Check to see if the axle bearing has worn a groove in the axle and check the C clip to make sure there isn't excessive play.
 
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oldsmobile joe

Royal Smart Person
Nov 12, 2015
2,067
3,053
113
mpls
for a wheel stud you'll need around .005" interference fit and no less than .002" A 12.5 mm drill bit will open the hole to .492" which will be good. You can get a more accurate hole with a reamer but they get kind of expensive.
thank you, thats the kind of info i was hoping to get. i checked my fraction drill set, i need something between 31/64ths and 1/2. i'll need to do more research, but either way, its cheaper than two axle shafts.
 

pontiacgp

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Mar 31, 2006
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Kitchener, Ontario
thank you, thats the kind of info i was hoping to get. i checked my fraction drill set, i need something between 31/64ths and 1/2. i'll need to do more research, but either way, its cheaper than two axle shafts.

if you drill with 31/64" even with a drill press the hole will be probably in the .490" range. Drills are not very accurate. There is no drill size inbetween 31/64 and 1/2 but you can buy a .495 reamer for around $30 and there are some machinists out there selling used reamers
 
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