Laminate Countertop Miter
The mitre is a pre-cut angle on the end on a countertop. The two most common angles used are 45° and 22-1/2°. Two 45° angles create a 90° miter corner and two 22-1/2° create a 45° miter corner.
The miter sections also have a mortise (Fig.1) cut into the under side of the countertop to fit miter bolts (Fig.2). Miter bolts fasten the left and right miter sections together. A spline (Fig. 3) can be ordered as an option. The spline is a thick piece of laminate that is to be glued into a slot that is routed into the edge of each miter section (Fig.4). Splines help to level the seam because of the tight fit between the spline and the routed slot.
You should dry fit the countertops on cabinets. Countertops should be scribed to wall before joining sections (see scribing section page in 'DIY Help'). Exception would be if one leg of the miter is short, usually not longer than 48". Things to consider are accessibility, weight of assembled tops, number of people to help lift into place. Also check for correct lengths, overhangs, end caps, and overall appearance before proceeding.
Tools needed are; saw horses (min. 3, all the same height), 7/16" open end wrench, hammer.
Supplies needed are; miter bolts, spline material (if ordered as option), small thin piece of wood approx. 1/4" - 3/4"(T) X 2"(L) X 2"(W), water proof wood glue, caulk or colored seam fill, cardboard or drop cloth to catch glue squeeze-out that drips to floor, and wet rag to wipe excess glue from surface of miter joint.
How to Assemble Miter
- Place countertop sections to assemble on saw horses laminate side up. Place cardboard or drop cloth under area of miter to catch glue that will drip from miter joint. Dry fit the miter together, making sure the fronts (noses) and back splashes line up. Also check alignment of mortises, making sure they are parallel to each other.
- Separate miter and apply a liberal amount of waterproof wood glue to each side of miter section. If a slpline was ordered also apply glue into the routed slot on each miter section and insert the spline into one side of the miter (Fig.5).
- Now you must work quickly. You have about 15-20 minutes to finish.
- Mate surfaces together, line up the noses and put in miter bolt closest to nose and tighten with 7/16" wrench just enough so it will not fall out.
- Check seam at back splash, if not level move sections to level, then put mitre bolt in mortise closest to back splash and tighten enough so it will not fall out.
- Now work your way down the seam installing the remaining miter bolts and tighten enough so they will not fall out.
- Using a damp rag wipe glue squeeze-out off surface of laminate, taking care not to get water in glue joint. Water in glue joint will weaken the glue bond.
- Starting at the nose, check level of surfaces. If one side is high place thin block of wood on high side and tap with hammer to level (Fig.6). As the nose becomes level, tighten miter bolt closest to nose. Don't over-tighten, this will prevent the area to align next from moving and can also damage the mortise. If a spline was ordered be careful not to over-tighten the miter bolts, the slot for the spline slightly weakens the mortise cutout. Don't hammer directly above the mortise, this area is thinner and can be damaged. Work your way to back splash leveling and tightening as you go.
- When you are satisfied with levelness of the seam, wipe up any remaining glue from surface.
- With seam dry apply caulk or colored seam fill to the joint. Follow manufacturers directions for applying and clean up.
- The joint must dry COMPLETELY before moving. Follow glue manufacturer's recommendation for drying time.
Click on images to enlarge.