Originally Posted by
andr0id
Make friends with a skilled machinist who has access to a rudimentary lathe.
Take the spindles out of your good pedals and ask him to make you spindles that are exactly the same, only with 1/2" threads. (Don't forget to point out the LH and RH threading)
Buy him a 6 pack when he's done.
I see now you've said to make new spindles not adapters. Still, a PITA as not only will the custom spindles be not nearly as hard, and therefore much more wont to wear, but SPDs aren't exactly easy to take apartt- hey have that weird plastic splined nut on the crank arm side that takes a proprietary tool that isn't easy to improvise with damaging the nut.