Building a corian countertop

  8: Now that you have your tools close by you can start by trimming the "onion skin" and remove the sink cut-outs. We cut 95% through with the CNC because of the type of vacuum system we use (cups). If we would cut all the way through the machine would bind up with the loose part and break bits, or more expensive parts. Next we flip the tops upside down, and drill starting points in all the holes and cutouts. Drill with something like 5/8 or bigger allowing you clearance for the flush bit. Remember to cut slow and be sure to cut all the excess so its only a flush edge. Support your workpiece so it doesn't crack when you only have two inches to go.

this just shows how the cnc cuts our material.

  9: While the counter is still upside down, use the round over bit in all the sinks, don't forget these sinks are undermount and need a finished underside as well. After rounding all the sinks you can go ahead and sand them to a finished feel. No one will ever see these, and it only has to "feel" smooth. When that is done you can glue on your build up.

   10: Lets add the build-up. In this paticular situation our build-up is only 1" due to an existing support beam on the job site. Before gluing, sand the faces that will join each other with a rough grit paper to ensure a strong bond for the glue. Next you'll want to bring over your basket of spring clamps (A-clamps). If your doing six tops like us thn you can rotate by mounting three buildups at a time. This glue sets quick so be prepared to move fast. It might help to have someone there to back clamp everthing you just set. Lets pull the glue out. Wipe everthing you sanded with denatured alcohol, to allow a clean glue surface, free of debris or chemical.

Make sure you have plenty of mixing tips, as each use will render it useless after the glue sets. Set all the build ups close to their edges where you'll mount them. Apply a liberal bead, I use three, front and back on the top, and one center on the actual build up itself. (By this i mean only the front edge of the countertop where it'll actually sits so there is three lines of glue holding.) Pump out some glue before applying to workpiece to ensure adequete mixture. (I've made that mistake and stuff never dried) Run the beads on one top, flip the build-up over and clamp sparingly at first. Be aware of the piece slipping forward and backwards. Once you got that straightend out have you helper place the rest of the clamps as you move onto the next top. Your mixing tip should still be wet, but squirt some out, so if any setting occurred it wont interfere with your glue job.

Glue should squeeze out all along the entire edge. 

  11: Move systematically from one top to the next. Make sure after your helper back clamped that glue is squeezing out all along the edge, the entire edge needs squeeze out so you will have a nice finished front edge upon completion. You will router this smooth later, don't wipe it or scrape it let it harden. Once three tops are glued go back to your fist one and scrape excess glue from behind the build-up. A regular putty knife should do it, the glue should be slightly setting and a lot thicker, but soft enough to remove. This makes our life easier when it comes time to mount the apron.

  12: After 1 hour (they suggest 20mins) try to dig your fingernail into the glue. If it indents but doesn't smudge you can safely remove the clamps. Stack them on your next tops so you don't have to pick them up again. Repeat the previous steps on the next three tops, dont forget to change you mixing tip. Once everything is dry you can set a straight edge and trim the excess glue + 1/32" from the front edge revealing a smooth easy to sand finish.

Cutting the front edge                                                              Easy to sand router finish

You can go ahead and finish sand (everything except buff), the face and the underside of the buildup now as the apron gets attached after the next step. This job calls for an 1/8" roundover, so sand everything right up to 4000grit.

    13: This paticular job we had three walls, and backpsplashes on all three, so to make our install easier we cut back about a 1/4" all the way around, this minimizes scribing and cutting in the field. We leave about  1 1/2" - 2"  from the front edge. Now the only scribe is a small piece in front, easy enough with a belt sander.

before                                                                                      after       

   14: Once all the build-ups are glued and cured you can start prepping the apron, finish sand the faces before gluing.(makes your job easier later on when you only have to touch-up and buff instead of going through 8 differnt sand papers). It's always easier to work on a flat suface at your standing height, No slumping! Sand the aprons all at once, might as well they're there, and your helper can do half. Sand in a normal fashion. Start with rough and work your way up to a gloss.(I won't explain sanding here as this is a build how-to.) We used the new mirka papers,  abronet is a mesh paper the dulls rather quickly. The abrolon is a pad for the micro grits which can be used wet or dry. We only used wet from 1000 grit and up. The steps are as follows: 120,220,320,500,1000,2000,4000,buff pad and compound, then a final polish.

   15: Once the aprons are set, I went ahead and cut a bunch of 5 x 5 squares out of scrap wood. We will hot-melt glue these behind the build-up about 3/4 of an inch back to allow space for the corian (1/2") and our shims to apply pressure. They can be easily removed afterwards, and are quite handy for keeping the apron square during the glue process.

   16: Now we're ready to install the apron,  re-wipe everthing that will have glue on it with alcohol again. Make sure the piece dry fits with no interference. Look for glue left behind or debris that got in there from.... you never know where it came from. Lay the apron on top of your jig pieces and lay a nice hefty bead of glue. (this is all that hold it on so dont be skimpy) Do this on all surfaces meeting another surface. Start again systematically inserting shims between the 5 x 5 pieces and the apron.. Keep a square handy because you should refer to it periodically,(like every shim).

As you put the shims in place continually check square. You do not want to be out of square. First of all it is the strength of the top. Secondly the G.C. will see it a mile away and you'll be rebuilding, Not fun. When all the shims are in good and tight go ahead and put some vertical clamps on so you have a good solid bond. Again let that dry for 30mins to an hour, we let these sit over night.(sorry no pictures of it actually clamped up.) There's a little showing in the below pic.

  17:  Once the aprons have dried you can take off the clamps and inspect for touch up sanding/buffing. Since you did most of that earlier it should be minimal. Go ahead and touch those up, remove your blocks, cleanup any residue with a chisel. Flip the counters and head to the next step.

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