I do not agree: a Belt sander with a fixed, too high speed and too coarse belt is indeed a NO-NO... (for example, a Makita 4" x 24" without speed control, a brute force machine that is only good for aggresive work and not at all for any finish!)
BUT; a variable speed belt sander equipped with a not too-agressive grade belt is advantageous when you have to remove old coatings or deep blemishes. The trick is using it at its lower speeds. Some belt sanders can be fitted with additional base plates to avoid going too deep. Mine is a not-a-top brand Skil 7640 variable speed 3"x 21" 900m watt belt sander. It can lower its speed far enough to tackle some resin or even plastics sanding without quickly overheating and melting the surface! Leaving a belt sander for too long at the same spot or moving it too slowly along the surface can heat the surface too. The base plate that it came with, is advantageous after you learn how to use it, and also take the time to slightly bend it to the proper shape, and take into account that too thick sanding belts will protrude too much and "eat" or gouge the wood surface!, but taking care to select the thinner material sanding belts, the belt will be kept at the best depth and only remove the very top of the surface (the old varnish) and not too much of the wood below.
As others have already said, a good dual action random orbit sander, preferably with forced rotation first, followed by the random mode (non forced rotation) is best for finishing large surfaces, like a 8-person dinning table, or a Concert piano or even a bedroom's floor. In that way, the belt sander helps a lot in speeding the large work, and the dual action random orbit sander can remove all coarse marks from the initial sander, and will reach a fine finish sooner. In my case, I have an old Random orbit Bosch PE12AE about 380 watts, and after years of using it, decided that all of the random orbit sanders with 125mm platten and less than 600 watts are a waste of time!: meet the newer really powerful ones from Bosch, Festool and Makita, with more than 700 watts and FORCED ROTATION (Dual mode: forced geared rotation, and free-spinning "random" orbit)... As the Festool is way too expensive for me, and the Bosch has some issues with plastic gears breaking, I bought the Makita BO6050, and find it slightly unrefined, somewaht noisy and slightly vibrating, but powerful and fast, and at the same time capable of fine finishes in its final non-forced rotation "random" mode, like having two machines in one. Thus, by attacking the job with the Skil 7640 belt sander AT LOW SPEED, caring to use thinner belts of not too coarse grade, and then following with the Makita BO6050 on the powerful forced rotation, and then finishing on the less aggresive random mode, I can tackle large surfaces in an efficient and fast way. I have only kept the old Bosch 380 watt sander-polisher for smaller jobs, and because I have collected numerous accesories for it, but find it too slow and lacking power. For that reason, I do not recommend any of the numerous under 600 watt random orbit sanders from the many brands like DeWalt, Milwaukee, Ryobi, Ridgid etc., but do recommend the powerful Makita or Festool (if you have the money and enjoy spending so much!). One word of caution: the powerful sanders I have mentioned DO indeed take some LEARNING to master, as they can produce damage if not carefully used. but with a little practice and use, they are the way to go. Finally, the much admired Mirka Deros seems to me as a fine machine, but it is expensive for what it is and still lacks some serious power.
I must have or pressed by accident
