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I’m in the process of making a form for pouring 1-1/2″ thick concrete countertops. My wife and I both like the idea of getting a nice round bullnose on the edge of the counter. Over the weekend, I experimented with routing out a 1-1/2″ channel (with a 1-1/2″ bullnose bit) in a 2×4, and then attaching it to the melamine-coated particleboard that I’m using for the rest of the mold. This did result in a concrete slab with a pretty nice bullnose, but I don’t own a shaper or a planer, so the flat edge of the 2×4 (that made the seam with the particleboard) was only as smooth as my table saw could get it (with a new blade). Consequently, I didn’t get as tight of a seal (between the 2×4 and the bottom of the form) as I would have liked.
So, I had a few thoughts. One was to glue up three sheets of MDF… that would give me a good factory edge against which to rip (and to route). However, I’m worried that the router might not “play nicely” with the glue.
The other (wackier) thought I had was to put a dowel in the mold, and then put some of that foam insulation in on one side of it. Remove the dowel and… voila… there’s my bullnose. I tested some insulation in one of my concrete samples… it held up remarkably well (so long as the insulation was dry once I tried it).
We also tried a piece of cove molding, but didn’t really like the ridged look that it gave the countertop.
Does anyone have any other thoughts on how to get a good bullnose? Or thoughts about routing glued-up MDF panels?
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John,
I built a concrete canoe and to create a smooth edge at the gunwale I ripped PVC pipe length-wise in the table saw. Find pipe with correct inside diameter (might be schedule 20, 40, class 200, dwv, etc.) Worked perfectly for me.
*Adding onto Mike's good suggestion, I did this for an outside corner in a poured sunken living room floor and it worked nicely. What worked for me was to run the pvc carefully through the table saw so that you slice the cut edge at a tangent to the inner surface. If you just rip the pipe down the middle, for example, you'll be left with a lip the thickness of the pvc wall. Do that, but then flip it another 90 degrees and slice off the thickness of the pipe away to leave a pointy edge. Then you can lay it flat on your countertop formwork, add some blocks to hold it level, and you're ready to go.
*Man... this is great. Simple, and SO much less expensive than buying a router table (not to mention the bit). One question... what kind of blade do you use for clean ripping of PVC? Will a combination blade do, or do you want a smooth cutting blade?Thanks for the great idea... I'm going to go try it tonight!
*I just used whatever cheesy blade was there at the time. You never have concrete against the cut, so anything that'll do the trick. Though it's quite possible I used a hand saw. It was 2 years ago and I honestly don't remember. (Don't remember yesterday's lunch, for that matter.) Experiment first to make sure you like the result. The trick is supporting the pipe for cuts 2 and 3 so that as you rip the tangent and get a sharp point on the pvc wall, it doesn't collapse on you against the table saw top, be/c it does get pretty thin. Also, find a method that works for you so you don't spin pipe as you rip it, creating a bit of a spiral cut.
*If you'd still like to go with wood for a form, you can often have wood jointed and planed at a local shop. I've had a local guy run a few boards through and charge me $10. You want it jointed first, to make it straight, then planed, to make the opposite face parallel to the first.
*Use a hollow ground planer blade in your table saw and you can use the wood edge
*I don't care how careful you are making the perfect seam...wood, PVC, MDF, whatever. If you can feel a seam in the form, you'll see a seam in the concrete. I lined my forms with vinyl sheeting. Voila...no seams!
Hi Dave,
I poured my own concrete countertops. The problem was with the seams.
One was about 12 ft long and another was about 5'x6'. So I ended up with a 6' seam and a 24" seam on the 12' countertop. Used 4'x8' malimine.
Wish I had found the "Breaktime" site first.
Could you give more detail on how you line your forms?
Im sure I will be building more countertops, everybody that comes over loves them.
Rob
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I'm in the process of making a form for pouring 1-1/2" thick concrete countertops. My wife and I both like the idea of getting a nice round bullnose on the edge of the counter. Over the weekend, I experimented with routing out a 1-1/2" channel (with a 1-1/2" bullnose bit) in a 2x4, and then attaching it to the melamine-coated particleboard that I'm using for the rest of the mold. This did result in a concrete slab with a pretty nice bullnose, but I don't own a shaper or a planer, so the flat edge of the 2x4 (that made the seam with the particleboard) was only as smooth as my table saw could get it (with a new blade). Consequently, I didn't get as tight of a seal (between the 2x4 and the bottom of the form) as I would have liked.
So, I had a few thoughts. One was to glue up three sheets of MDF... that would give me a good factory edge against which to rip (and to route). However, I'm worried that the router might not "play nicely" with the glue.
The other (wackier) thought I had was to put a dowel in the mold, and then put some of that foam insulation in on one side of it. Remove the dowel and... voila... there's my bullnose. I tested some insulation in one of my concrete samples... it held up remarkably well (so long as the insulation was dry once I tried it).
We also tried a piece of cove molding, but didn't really like the ridged look that it gave the countertop.
Does anyone have any other thoughts on how to get a good bullnose? Or thoughts about routing glued-up MDF panels?