[ToddF]

Most bearing races are extremely hard. So hard they are normally ground rather than machined. You are more likely to trash your reamer than to open up the bearing bore.

The drill rod, on the other hand, is supplied in an unhardened condition. Notice that the page says "water hardening", not "hardened". It is quite easily worked. It is designed to be worked to shape and then hardened by the user for use in tooling. You should be able to chuck it up and hand work off .0005" without too much trouble, using fresh silicone carbide abrasive paper. It's not fun, but doable, especially if your bearing is going to be installed near the end of your shaft. I wouldn't want to have to polish the whole shaft to slide a bearing all the way down it, though.

Notice that the drill blanks, at the bottom of the page, are hardened and ground to size. The tolerances are much tighter. You wouldn't want to try working the diameter on those.

You can tell the difference by using a fine file and attempting to file the material. On unhardened rod, you can easily file a chamfer on the corner. With hardened material, like a drill bit or bearing race, you will be lucky to scratch it with your file.