I use a lot of different pen blanks for stem material. They are usually 3/4" square which is big enough for most stems. Also they're available in about a million colors and patterns.
Check out what Penn State Industries or Exotic Blanks has to offer.
Yes, when I come to think of it even though there is a multitude of rod stock available to make pipe stems there are times when some stem designs when one must be able to turn one out of square stock.
I think I was more in the realm of thinking, and or the concern about the choice of material that is available/conducive which should not be used as many can be toxic, or at least cause some caution. Many woods and synthetic materials, albeit beautiful, should
never be used for a stem. Some that could possibly be of concern are: Alder, Ash, Beech, Birch, Bubinga, Ebony, Maple, and there are others albeit most of them would not be considered for making a stem. Then of course there are some synthetic materials which abound and would not, in my mind are safe. One that immediately comes to mind and that I’ve used extensively for making knife handles would be MIcarta which comes in a multitude of various designs and is quite beautiful. However, it is made of phenolic resin which contains phenol and is considered to be quite toxic to humans via oral exposure. I’ve worked with a multitude of exotic woods and synthetic materials, but I’ve always worn a respirator while doing so. Just because some material is beautiful and available (pen blanks) and seems like the ideal answer to making that ‘special’ stem one should step back and take extra caution. All that ‘glitters’ is not safe is all that I’m trying to say. :wink: