All these answers about purchasing files and dies require more money than just getting another axle. The comment by oneclick mentions tracytools. I looked at the webpage, no dies in this tread size. Americans will not be able to purchase anything shipped using post from outside of the USA starting today due to onerous import restrictions. Here is a NOS genuine Campagnolo Record rear axle that is suitable for a 6 speed, 126 OLD hub as shown in the original post. $20. I also have a NOS Gipipemme rear hub that has a M10 x 26 tpi 55 deg threaded axle. It is about 6mm longer than the 6 speed Campy axle. The cones, balls, locknuts and washers all interchange with the Record rear hub. This axle does not have grooves for the tab washer. The hub body has a French freewheel thread, M34.7 x 1, not very useful but the axle hardware is. $20. Shipping at my cost, should be around $5. Jim Merz