Wayne, Ive never used me but I have read about them. I thought they were called forge wood shafts, for some reason the name Bill Sweetland rings a bell.
I've thought many time if they could be made on a small production scale for personal use. I had considered that a 20ton press in one of those big metal arbors might be enough force to compress the wood.
IIRC they were made by cutting a board thick at one end and thinner at the other end, then compressing it to an even thicknes, thereby making one end more dense. Then square blanks were ripped from the board, and then turned into shafts.
So if you used a press, you'd need to attach two very rigid plates to squeeze the wood between.