I used it to cut glass backsplash but have to go REALLY SLOW!!!!! there may be some chipping.
The center bushing acts as an adapter. Not all tools have the same size arbor/spindle. If the tool has a 5/8" arbor/spindle then you will want to leave the bushing in so that the blade fits tightly to the arbor. If the tool has a 7/8" arbor then you will need to remove the bushing for the blade to fit on the tool.
No, they would be dangerous, wood can jam the saw. I have seen a double blade saw that cuts all kinds of stuff though. It is called a double cut saw.
I tried this blade and it chipped the tile quite a bit. I ended up buying another brand for a smoother cut. There is some technique as well but I won't use these for my tiles unless they're very soft tiles I also wanted the other 1/2 of blade the other brand offered, 4 inch was less than helpful.
This is a flat blade. I had to gurgle the type 27 blade and found this on a forum "For a 4.5" right angle grinder, is one wheel type better than the other? Grinding and cutting discs are available in both Type 27 (depressed center) and Type 1 (flat) versions. " I don't know why any grinder would only use one type of blade. I've tried this on my D_walt and it worked, though I didn't like the performance.
Yes, this blade can be used with a 4in wet tile saw.
Yes, this blade will cut quartz.
Nope. My grinder is a 4 1/2" Milwaukee. Actually for cutting register vents and outlet box holes in tile I prefer the smaller diameter blades. The smaller diameter works to your advantage when making difficult / complicated cuts because you can cut closer to your cut line. For example... think about how hard it would be to cut a hole for a 4" electrical outlet using a 10"in blade. You would not be able to plunge deep enough to penetrate the backside of the tile before the saw started cutting beyond the top and bottom edges of you guidelines for the hole. When cutting holes for toilet flanges and electrical boxes I prefer a 3 1/2" blade as it allows you to penetrate the backside of tile and cut up to edges of reference cut lines.