You're looking to do it the wrong way. Buy a 530 to fit the shaft and then have one or both sides surface ground down to the 525 thickness needed, roughly a total of .060" or so thinking. More room for error and not having to perfectly center the hole like you plan on. As well you can grind only one side to more perfectly center up with the rear if you need to move sideways any for better chain alignment.
The inner splines are generally case hardened and the machine shop will hate you for forcing them to cut that, it kills tooling. As well your new work won't be and will wear very fast.
The outer teeth are hardened too but the sides will not wear as fast because not nearly the load on them as the teeth. If you had some way to mount sprocket on a shaft to spin easily like a trans shaft with bearing on it you can even hold the bearing and let shaft/sprocket spin against a bench grinder wheel to cut it yourself...........BTDT.
A machine shop with a rotary table can easily cut the sides down on a sprocket. Or on a lathe with a tool post grinding setup. Cheaper too.
You can even run 530 chain on 525 sprocket but the wear will be funny after a while. Pitch is the same, only width change there.
