9/16 thread pedal adapter for vintage dura ace cranks?

i picked up a pair of vintage dura ace cranks with the intent to use them on a bike i am restoring. only problem is that they have a huge hole for the pedal threads. not 9/16 or even 1/2". they had really old christophe toe clips on them, the hole for the pedal is about an 1" wide.

are there any adapters to go to a 9/16 thread?

It sounds like Loose Screws sells the adapter you may need for those old AX Dyna Drive arms. However when considering the cost you may want to re-think it and get some other arms. Any way you can go here:
http://www.loosescrews.com/index.cgi?d=s...

BTW .. I have heard some talk about those arms cracking much too easily. But that's just talk. All cranks can crack if improperly maintained.

I am sorry to say that there is no adapter or anything else you can use.

Awhile back Shimano tried to popularize a VERY large pedal thread. The idea here was to allow a supposedly better pedal stroke that could be had by offsetting the pedal.

They may have had something but could never provide proof that it actually worked so it faded into oblivion.

Your only options are to find matching pedals or to replace the crank. Sorry.

EDIT: Guys, a helicoil would be a good option but the hole is too big even for that. The machine shop is also a good idea but pedal threads have goofy profiles and require a very experienced (read: expensive) machinist to reproduce. I did the same thing once... had someone machine something over their lunch hour (actually they did it after hours) for a meatball sub. Mmmmm.

You could have an adapter made. Machine shops do this kind of thing all the time. The best of all possible worlds is that you have a friend who works in such a shop who will manufacture the necessary adapter sleeve for you in return for a case of his favorite beverage (worked for me, once).

HTH

There's another possible option: check a shop to see if they can use Heli-Coil screw thread Inserts. Many expensive and important parts have been saved this way.

28 years in the industry is impressive but evidently not long enough. Shimano introduced this crank/pedal design in the early 1980s and did manufacture an adapter to go down to 9/16" standard pedal threads. Many of these cranks sold nowadays still have the adapter in them.

If you can't find one on eBay then you can have one made easily enough, as mentioned.