The Ridgid contractor saws are directly related to the older Cman saws....out of the same two factories, and many parts are even interchangeable, so I'd definitely include them. The Ridgids have a better fence....some of the Cman have an "Alignarip" that's a similar style, but some of the old ones had a skinny steel fence that's kind of quirky....ok to buy at the right price, but with the understanding you'll probably want to upgrade the fence some point. The Delta T2 or T3 fence is ~ $190 at HD, so keep that upgrade in mind as you price a used saw.
As jussi mentioned, a riving knife is a "nice to have", not a "must have"...a splitter does the same task if you use one. Some saws are a compact style, and won't be quite full size...the indicator is depth of the cast iron table from front to back - 27" is the standard full size depth. Belt drive induction motor vs universal direct drive is another biggie to look for....the older standard contractor saws have an outboard belt drive motor hanging off the back. Some newer designs move the motor inside. Running it will tell you in a heartbeat if you are not sure....universal saws scream like a circular saw, induction motors hum like a fan. Solid cast iron wings are a nice to have too, vs stamped steel....I wouldn't walk from a right priced good saw because of steel wings though!
Some of the Grizzly contractor saws have basically the same guts as the old Jet and PM saws, so those can be good depending on the fence....there are many older saws from a variety of lesser known names that essentially have the same guts from the same Mao Shan factory....Ohio Forge, Bridgewood, Woodtek, Omega, AFF, Mao Shan, etc. If the price is right, the fence can be upgraded if need be. To me $50-$150 is the right price for those. Old Rockwell contractor saws are about the same as some of the older Delta....beware of the cheaper direct drive models though....look for the motor off the back and a full size table.
jussi - yep Geetech!
Hi - Welcome to the gang. Dust collection has a lot of things that need considering to engineer the system correctly. Here is a book that can give you a decent place to start:
Then you might give Bill Pence's website a look, although he may scare you a bit.
Something to think about: a 2 HP dust collector can change or exhaust the air in a 40 x 40 foot shop in 20 minutes. If you are going to air condition you shop, you are going to need a way to return the air the DC is moving back to the shop.
I think it is pyrolized wood, a type of heat treatment that colors the wood all the way through. It also renders the wood rot resistant without using chemicals.
i think the wood has to be heated in a chamber without oxygen or some special atmosphere.