I lost count, but I think I have now applied about 12 coats of polyurethane. Nearly 1/2 gallon. After about 7 coats, the endgrain finally stopped soaking it in. So at that point, I basically had a 3/32” thick “plastic” top, as hard as a butcher block. Which is exactly what I wanted.
I tried to put the poly on as thick as possible, sanding down all the high spots between coats. After the 7 coats, I realized it wasn’t as flat as I’d like, as I was sanding through the poly in some spots, but not in others. So I took my scraper, and scraped off all the excess poly. The endgrain is so hard that the scraper wouldn’t cut into it. So now I had fully filled and sealed endgrain, with no poly on top. Then added another heavy coat of poly. At that point I stated wet sanding (using mineral spirits as the lubricant) with a wood block and 240 grit wet or dry paper. Got it smooth as glass, then another coat, and wet sand again. Still sanding through the poly in spots, though. But since I’m happy with the flatness, I thinned the poly down, and applied a really thin coat. Waited 2 hours, and added another.
Went out last night and used the ROS and 220 grit, and took off all the shiny spots, then rubbed with steel wool. And saw that I’ve still sanded through the finish in spots. I could wax it and leave it, as no one would really notice, but instead, I added another coat of poly.
But before the poly, I loaded it back on the CNC, and re-routed the plate opening for the last time. It wasn’t quite deep enough, so I went down to nearly 1/2”. Then I put an 1/8” bit in, and routed pockets for the heads of the leveling screws, and a starter hole. I’ll drill a small block on the drill press to help me finish drilling the holes perpendicular to the table. Then I’ll tap them and use 1/4-20 stainless button head socket screws to level the plate. The plate will be 1/2” phenolic, with a slight rabbitt around the edge. I’m going to make 4 plates, 2 for the 690 base and 2 for the 7518. 1 each with a 1” hole and 1 each with a 2-1/2” hole.
Here’s a close up of the Bubinga edge. You can see a small patch that I used to fill in the gaps when laying down the blocks.
I was going to get some stainless angle to mount the table to the saw, but I came up with an easier solution. I measured the 1/8” plate that was already mounted to the saw, and used the CNC to make a cleat to screw the table to. It’s 1” baltic birch plywood, notched around the 3 large bolts that hold the plate to the table. I’ll also use the stock Delta angle for the front and back.
So, after I spend half the day in the yard, here’s the plan. Sand the last coat of poly. If I sand through again, I’ll thin the poly and wipe on two more very thin coats tomorrow, and steel wool to finish. I need to pick up some wax at HD today.
Throw it back on the CNC, and route the holes to access the T-nuts.
Make a jig to locate and drill the mounting holes in the top, and countersink them. Set it in place and bolt it down. Make some temporary legs to hold it up. The cabinet to go under it will have to wait until the fall.
With any luck, I’ll have it mounted tomorrow. At least by the end of the week.
Hopefully as soon as it’s back together, I can clean up the garage enough to do some work. I need to design a new fence to bolt to the Incra Jig. It’ll have vacuum, and T-nuts for featherboards and fixtures.
Here’s an AutoCAD screenshot with the Incra Jig attached.
-- Gerry, http://g-forcecnc.com/jointcam.html