It is probably ground rod, a grade of stainless steel (they never rust!) which is then titanium nitrided. That process take place at about 180 degC, so it won't distort the shaft and is unlikely to temper it too much. The base metal itself is soft (easily dented with a pair of pliers, for example) yet tough - and that is the word!
The ground rod will be bar fed into a collet, the thread and grooves machined, then parted off to length. About a 15 second operation on an automatic lathe, probably less on a modern one.
Silver steel is useless, way too soft and only any good if hardened as it will rust. Drill blanks are too brittle, and all features would have to be ground which is too expensive. If you want to make your own, find a grade of stainless steel you can afford, see if you can get it as ground rod, and then turn in the features you need. HTH
