Carbide lathe tools are simple to make and substantially cheaper than commercial versions. I own a couple of Easy Wood Tools and my homemade versions work equally well. These are built with maple harvested from my property, 1/2" steel rod, and carbide cutters purchased from AZ Carbide. The ferrules are cut from copper pipe, fixed with CA glue and then polished.
Tips were shaped on the grinder then holes drilled and tapped for 6-32 screws.
Diamond and radius cutters. The diamond cutter is handy but the back corners have a tendency to catch. The radius cutter gets less use than I expected. My recommendation is use square bar for diamond, radius, and square cutters as it will give more support and help prevent the tool from rolling in your hand.
Finished handles. The size and shape is very comfortable but are front heavy, I may go back and add weight to the handle. [update: balance hasn't been an issue since the tool rest supports the front but I'll use a heavier wood on future handles]
In a former life this beading tool was a file, now it has a handle to match the others. Shape of the bead is cut into the handle so it's profile is known at a glance.
Long term update: In addition to these I also own Easy Wood Tools and a variety of gouges, skews, and parting tools. In general, I get a better and faster cut from gouges than I do from carbide tools but the carbide scrapers come in handy for very hard woods and roughing in general. If I were to do this over, I would use square bar for square, radius, and diamond shaped cutters because they need the extra support and it will help prevent the tool from spinning in your hand. Round or square bar is fine for round cutters.