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How to Make a Seam in a Plastic Laminate Countertop

There is a proper way of making a seam in Formica so that your plastic laminate joint comes together tight on the countertop surface. Once you learn how to make the joining of the two pieces fit together nicely, you can apply this method to any areas of cabinet making where a seam is required.

Always cut your material plenty oversize, just in case you have to do this procedure more than once. I usually allow an inch to an inch and a half more on the materials length and width.

Tools Needed to Make to Tight Joint in the Formica Pencil

  1. Pencil
  2. Small hand held router 
  3. Straight laminate cutting router bit with a solid cast pilot guide (not ball bearing) on the end.
  4. ¼” to 3/8” thick dowel rods. You will need enough rods to place on the countertops surface about  6” to 8” apart from one another, the entire length of your longest piece of mica that you will be sticking. These will act as a protector between the contact glue on the top and mica while you are adjusting the plastic laminate to be in the exact position you need it to be in.
  5.  Flammable contact glue
  6.  Lacquer thinner and rags
  7. Glue Applicator, either roll it on, spray or brush the contact adhesive on the surfaces.
  8.  Hammer
  9.  Two straight edge ¾” thick boards that are about 8” wide and 6” longer than the length of the seam.
  10. Four large C-clamps or Jorgeson clamps.
  11.  Six or more hand spring clamps or any other type. These will just be used all along the counter to hold the laminate in place.
  12. Aluminum foil if you are using particle board underneath the seam.

For a more complete list, check out this article listing the Tools Needed for Plastic Laminate Work.

  • Tip: Do not use a beveled laminate trim bit for this process. Because the cutter is angled, it will place a slight angle on both pieces of the Formica and the seam area will not look like it is tight because of the slightly beveled pieces.

Making a Professional Looking Plastic Laminate Seam

These steps will walk you through the process of making an almost unnoticeable union in the mica like a professional would. When your work is finished, the plastic laminate seam will be something to be proud of.

  1.   Sand the surface of the counter top where the seam is to be made.
  2.  If you are using particle board, laminate the seam area with aluminum foil. This will protect  from eventually getting a  water damaged counter top seam.
  3. Draw a pencil line where the seam is to be made from one point to the other.
  4. Place one of the 8” straight edged boards exactly along the pencil line. This will be the guide that the router will ride on when you are cutting the two pieces of plastic laminate when making the seam.
  5. Lay the remaining eight inch wide board, parallel, one inch away from the other one. The idea here is that the router will be able to set level on the two boards while you are making the seam cut.
  6. Lay the two pieces of plastic laminate into position over the top of the 8” wide boards, being careful not to move them at all. Adjust the pieces of Formica so that there are equal overhangs all around the countertops edges. You should do this with your tape measure. If your laminate is 1 ½” wider and longer then you should have a ¾” overhang all around.
  7. Use the spring clamps and place them all around the top to hold the laminate in place. Do not use these around the seam area where you have your seaming guide boards set up.
  8.  Using the large C-clamps or Jorgenson clamps, secure the mica, both boards underneath and the counter together on all four outer edges of the guide boards.
  9. Adjust the depth of the straight router bit deep enough to cut through both pieces of the plastic laminate.
  10.  Fire up the router and make a steady cut through both pieces of Formica using the proper guide board underneath for the router bit pilot to ride against. DO NOT stop while making this cut. You must push or pull the router at a pace that will not chip the laminate because you are moving too fast and will not burn the guide board underneath because you are moving too slow.
  11. Loosen the clamps that are holding the guide boards, but do not remove the spring clamps. It is critical at this point to not move the laminate pieces from where their positions are in relation to each other.
  12. Remove the excess pieces of plastic.
  13. Using a small straight edge, mark a pencil line across both pieces of the plastic laminate at a 90 degree angle to the seams edges. Make three marks, one in the front of the top, one in the middle and one on the back edge area. These will be used to help align the two pieces together exactly the way they were cut.
  14. Remove the piece of Formica that is not aligned (1/4” away from) with the seam line on the countertop. Then, carefully take the guide board out and then make pencil marks on the countertop that match the pencil marks that you previously put on the plastic. This will help you get the mica in its exact position when it is time to contact glue it into place.
    You can now remove everything and clean all of the router chips off of the counter and the Formica.
  16. Turn the laminate over and file the edge of the seam only on the bottom side. This is done to just clean up the edge a bit.  DO NOT file the seam on the finished side of the material.
  17. Apply the contact glue to the board and to the mica. Prior to sticking the two together, make sure that you clean the edge of the laminate seam on both pieces with lacquer thinner. Don’t saturate the glue though with the thinner.
  18. Once the glue is dry, place the dowel rods on the top six to eight inches apart. You should start parallel with the seam line and fan them out to a ninety degree angle. Then, lay one piece of laminate on top of the dowel rods. This is usually the largest piece.
  19. Align your small pencil marks that you made on the counter with the marks you made on the plastic laminate piece. Also, get the mica aligned with the seam pencil mark on the top. Check all the edges and make sure your mica is covering all around the top. Moving the dowel rod back slightly away from the seam, begin to stick just the edge of the plastic laminate to the line on the countertop.
  20. Once you are satisfied that things are aligned perfect and the edge is slightly stuck, begin to remove the dowel rods completely out, closest to the seam area. Press the laminate down as you are removing the rods. Continue to remove all of the dowels, sticking the Formica into place as you go.
  21. Lay the other piece of Formica on the dowels, align your pencil marks and push the seam tightly together. Follow the previous step of removing the dowels.
  22. Using a hammer gently tap the seam area down. Be careful not to tap where the Formica is hanging over the edge.

Now the counter is ready to be rolled, waxed, routed, filed and cleaned. That’s how a seam is made in a plastic laminate countertop the professional way. If you try to make one using any other method, it will not yield as excellent of a result. Making a good looking tight joint in laminate requires taking every step that I have shared with you and many that were not mentioned. You will have to take your time and think things through as you carry out the steps. If you have some colored caulking that matches the mica, rub it in the seam and clean the area off well afterward.

Categories: Making Counter Tops
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