I have a number of questions about zero clearance inserts for my table saw. A year ago I bought a piece of 1/2" thick phenolic to make several inserts for my 1992 Delta table saw. Well, as luck would have it, I didn't get to it and the motor on saw took a digger recently, and fortunately I hadn't made any inserts yet. Since the motor has the arbor integral and is $250, I convinced my wife it wasn't worth the cost and she let me buy a new saw! She's the best! Here are my questions:
1) I have a Jet JWSS-10LFR saw. The insert included with the saw is 3/8" thick with set screw levelers. The supports for the inserts are 1/2" below top of table. So I really need 7/16" or 3/8" thick phenolic to allow vertical adjustment. Can I put the phenolic through my planer to reduce its thickness without ruining the planer blades?
2) On after-market inserts I have noticed that they have a "gouge" on the underside as the start of the blade slot. What does this do and is this necessary?
3) What type of drill bit is needed to drill into the phenolic. Rockler has what they are calling a special bit w/countersink to drill phenolic (and it doesn't wander) for $19. Is that really necessary?
4) Leveling set screws - will they cut their own threads in the phenolic or should the holes be tapped first?

Thanks in advance for the help!