Sae Metric

Need a "M12x1.25" Standard Equivalent!?

Urgent,

While repairing my car, discovered previous owner cross threaded a critical bolt on the flywheel,

nonetheless:

The bolt that was improperly impacted was a m12x1.25.
Both the bolt and 1/2 of the hole was stripped, looking just to get a bolt in there for the second half of the threads still intact. The metric bolt is no where to be found.
Looked around locally and can't find a bolt with an appropriate strenth for its application. So i'm stepping to SAE. What would the standard equivalent be for this bolt?

Surely you could find a Metric bolt at a wrecker??
There's no direct equivalent. In SAE, 1/2" would be a little bigger in diameter, and for the pitch use UNF, 20 TPI is very close to 1.25 pitch.
Drill 29/64" if necessary, but try to at least start tapping using the bit of thread left at the top of the hole, if the tap starts differently you could end up cutting out the thread at the base of the hole.You need to be able to pick this up as near as possible.
The diameter difference is about .027" between the M12 and 1/2". Thus the UNF thread will still be very shallow at the stripped end, you will be relying on picking up the "good" section near the bottom.
Another possibility would be a Helicoil, to regain full thread depth.

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