I, and others, have looked for a belt sander that would meet the requirements for tool grinding and they are hard to find. Actually, any belt sander can grind a tool but adapting the tool rest to produce precise angles is the issue. I do know that the one I use can be easily adapted but that exact one is no longer made. A replacement with a slightly weaker motor IS available
here; I own this one, too and I know it will work. If you go for this one, there are a few caveats.
First, you have to use ceramic belts. At 1/3hp, the motor is not strong enough to grind tools with if you use standard aluminum oxide belts; it will bog down. However, the ceramic belts cut so well that the grinder is fully capable of grinding HSS lathe tools and I have confirmed this myself. Amazon carries the Red Label brand and I can testify that they are superb belts that work well for our purposes. I use the 36 grit for shaping and 80 for removing coarse grind marks but you might want to try their
assortment pack to see what works for you if you go this route.
Second, you need to make a decent tool rest and ideally use a ceramic glass platen liner. For what it's worth,
this article discusses the rationale behind this opinion and how I made mine.
Finally, I suggest you use a
wax stick lubricant when grinding HSS on these belt sanders. Just touch the stick to the belt for a few seconds to lubricate the belt and improve the function of the belt. This wax prolongs the life of the belt significantly.
Belt sanders make tool grinding so much easier. It isn't that a bench grinder won't work; it works well if you know how to use them. I used a bench grinder for tool grinding for over a decade so I know how it works but speaking just for myself, after grinding hundreds of lathe tools, it is my opinion that the belt sander is vastly superior for tool grinding provided you modify the tool rest and attend to that platen liner thing.