USE YOUR EDGE SANDER TO MAKE

PERFECTLY ROUND TABLE TOPS

          When I started making round table tops, years ago, I could never seem to get a perfect edge on the finished product. My technique was to use trammel points to draw a circle of appropriate diameter on the workpiece and then cut out the circle with a jig saw (saber saw) just outside of the pencil line. I would the use a sanding drum chucked up in an electric drill, mounted on a fixed base, to sand down to the line. It took a long time and the results were far from perfect but it was, at the time, the only sanding machine I had that could do the job. After all the finish sanding was completed, the final finish would often reveal scallop marks from the sanding drum and would clearly show that I had been unable to keep the sanding drum at a perfect 90 degrees to the table top at all times. Eventually, I purchased an edge sander to sand straight edges, as well as inside and outside curves. Of all of the woodworking machines in my shop, the edge sander has turned out to be one of the most used and useful.

            I discovered  that I could get better results making table tops  by using the edge sander but that I could not control anything larger than small tabletops, 24 inches or less in diameter. I wanted to make large tabletops out of solid hardwood glue-ups with diameters as large as 8 feet and thickness up to 2 inches. Whenever I find that I can’t physically control something on stationary woodworking tools, in this case an edge sander, I devise a woodworking jig to solve the problem. The drawing at the end of this article represents the woodworking jig I created. Combined with the edge sander, it works like a charm. Like any other production device, I would not go to the trouble of making such a woodworking jig for just one tabletop. However, I would not be without this woodworking jig if I planned to make multiple, round table tops.

            Here are step-by-step instructions showing how to make your own woodworking jig for the edge sander to enable you to manufacture large, perfectly round table tops with the edge sander. I'm sure this jig could be adapted for use with other woodworking tools such as a disc sander or, possibly, even with a horizontally-mounted belt sander.

 1) Start with the following shopping list if you don’t have some or all of the necessary parts or tools already.

(6) pcs.. 2 x 3 x 8’ fir, pine or white wood. If you can’t find 2x3’s, buy 2x4’s and rip them down to 2 ½ inches wide on the table saw.

(1) pc.. 1 x 2 x 8’ fir, pine or white wood.

(1) pc.. 4’ x 8’ x 3/4” particle board –OR- ¾” Melamine.

(1) Sheet 4’ x 8’ plastic laminate (not needed with the Melamine).

(1) Gallon contact cement with throw-away brush or squeegee (not needed with the Melamine).

(1) Rubber roller (not needed with the Melamine)

(1) Router or laminate trimmer with edge trim bit (not needed with the Melamine).

(1) ½” x 4” hex head bolt, bright steel.

(2) 3/8” x  3” lag screws, bright steel.

(2) 3/8” x 4” hex head bolts with (4) flat washers and (2) nylon-lined lock nuts, bright steel.

(4) 5/16” x 4” hex head bolts with (8) flat washers and (4) nuts, bright steel.

(2) pcs.. ¼” or 5/16” threaded rod 12” long (hacksaw out of larger piece, then sand clean and tapered).

(1) Hacksaw w/blade

(1) Set of trammel points –OR- a second ½” x 4” hex head bolt for a compass center pin (one or the other).

(1) Turnbuckle (1/4” or 5/16”) to match the tread of the threaded rod.

(4) Nuts and flat washers (1/4” or 5/16”) to match the thread of the threaded rod.

(1)  Box of 3” drywall screws.

(1) Pair of Vise-Grip pliers.

(1) ½” Forstner bit, (1) 3/8” Forstner bit and (1) 5/16” Forstner bit.

(9) 1 5/8” drywall screws (4) 1 ¼” drywall screws  and, of course,

(1) Edge sander of any size.

2) I am going to assume that you will want your finished woodworking jig to be 8 feet long for the sake of simplicity. I also realize that you may not have room for a woodworking jig that long in your shop, so, if you need to, make it shorter, but make it as long as you can. If you need to make it shorter, simply adjust the length dimensions that I give you downwards but proportionally. The width dimensions should remain the same as they are. Crosscut 2 of the 2 x 3’s to 96” long if they are not already that exact length. Crosscut another 2 of the 2 x 3’s to 93” long, making sure that both ends are cut square. Cut 1 of the remaining 2x3’s into (2) pcs. 39” long, each, making sure that all ends are cut square.

3) Refer to the drawing below. Build the following frame on a flat table, holding it flat to the table with C-clamps while you pilot drill and then screw it together. The two, 96” 2 x 3’s are the outside rails (joists), the two 93” 2 x 3’s are the inside rails and the two, 39” 2 x 3’s are the end caps on the frame underneath the table top. Mark the center of each of the end caps. Mark two lines, using a square, 6 ¼” to the right and to the left of the center marks on the two end caps. Pilot drill and screw together the two, inside rails to the two end caps, centering the ends of the inside rails on the two marks you just made on the end caps. Pilot drill and screw together the two outside rails to the ends of the two end caps, making a rectangular frame that measures 96” long by 42” wide. You should have at least 2, if not 3, 3” drywall screws going into each joint in the frame.

4) Apply a full coat of contact cement to one side of the particle board sheet and to the bottom side of the sheet of plastic laminate. Allow both to dry completely. Get someone to help you center the plastic laminate over the particle board before pressing the two sheets together. You only get one shot at this so I usually make sure that two of the long edges are lined up and touching before I smooth the rest of the plastic laminate out onto the particle board. Use the rubber roller, with as much downward pressure as you can muster to insure a good bond all across the sheet of laminate. Use a laminate trimmer or router with a ball-bearing laminate trim bit to true up the laminate where it protrudes over the edge of the particle board. If you don’t want to not want to go through the process in this paragraph, you can purchase a sheet of ¾” Melamine instead and save yourself the contact cement, rubber roller, plastic laminate and laminate trimmer.

5) Rip the particle board (or Melamine) into (3) pieces measuring 8’ x 14”. Crosscut one of those 3 pieces into (2) squares measuring 14” x 14” and one smaller square measuring 6” x 6”. Center and glue/screw (using (4) 1 ¼” drywall screws) the 6” x 6” piece onto the bottom (non-laminate side) of one of the 14” x 14” squares. Screw through the 6” x 6” piece into the 14” x 14” piece so that the screw heads are in the 6” x 6” piece and the plastic laminate on the 14” x 14” piece is not penetrated. Leave the other 14” x 14” square as is, for now. After the 6” x 6” square is glued & screwed to the 14” x 14” square, locate the center of the 14” x 14” square and (using a drill press) drill a hole through the middle using a ½” Forstner bit. Drill all the way though both the 14” x 14” piece and the 6” x 6” piece. As soon as the center pin of the Forstner bit pops though on the other side and before the rest of the bit comes through, go to the other end of the hole and drill back through, centering the center pin in the pin hole. This will insure a clean hole with no splintering or blow outs at the exit point.

6) Cut the ½” x 4” hex head bolt to a final length of just more than 2 3/16” from the hex head (where it meets the shaft) to the cut-off point. Place the 4” bolt in a vise and cut it off squarely with the hacksaw. Using the edge sander, sand the bold end flat (removing the hacksaw marks) to a final length of 2 1/16” from the hex head and then sand a bevel around the edge of the end that you just sanded flat. This will become your pivot pin. Hammer the pin first through the 6” x 6” particle board and on through the 14” x 14” piece it is glued/screwed to so that the end protrudes ½” above the plastic laminate. This assembly will be called “Car B” on the woodworking jig drawing while the other 14” x 14” piece will be called “Car A”. Using a drill press, drill (3) holes, equally spaced, into two, opposite edges of Car A, 3/8” in from the edges. These holes should be drilled using a drill bit diameter that just allows a drywall screw to be pushed through with your finger tip. Drill and countersink four more of these equally-spaced holes into just one of the remaining edges of Car A After these 10 holes are drilled, use a countersink on the drill press to make countersinks into the plastic laminate deep enough to insure that the heads of the drywall screws will not protrude above the plastic laminate. Crosscut (2) pieces from the 1 x 2 x 8’, each measuring 6” long. Depending on whether you purchased ¼” or 5/16” threaded rod, drill a ¼” or 5/16” hole through the exact center, vertically and horizontally, of each of the 1 x 2 x 6” pieces. Drill through the ¾” thickness, not the 1 ½” thickness. SEE THE DRAWING: Glue/screw these 1 x 2 x 6” pieces to the undersides of Car A and car B. They should be located flush with the edge of each car as shown in the plan. In the case of car A, the 1 x 2 x 6” piece should not cover up the screw holes previously drilled into the opposite sides but should cover up the 4 holes drilled into the side that is located at a right angle to “opposite sides” first drilled. The drywall screws used to attach the 1 x 2 x 6” pieces to Cars A & B should be countersunk into the plastic laminate, not the   1 x 2’s. Car B also gets four, equally spaced, countersunk holes for the screws used to screw the 1 x 2 to its bottom edge. All screws must not protrude above the plastic laminate or they will scratch your workpiece.

7) SEE THE DRAWING: Push one of the threaded rods through the hole you drilled into the center of the 1 x 2 under the edge of Car A but, before you do this, twist a nut and washer onto the threaded rod about 2 ¼” from the end with the washer on the side of the nut that is closest to the 1 x 2. Push the threaded rod though the hole in the 1 x 2. Place another nut and washer onto the end of the threaded rod where it protrudes through the 1 x 2. Tighten this nut securely with two wrenches, one on each nut. Repeat the above for Car B. The threaded rods should protrude (stick out) from the outsides of the 1 x 2’s. Screw the turnbuckle onto the protruding (longer) ends of the threaded rods, tying them together. Check to see that the 1 x 2’s and the threaded rods are oriented to each other as shown in the plan. The threaded rods and turnbuckles must be between the cars and the 1 x 2’s must be mounted under the sides of the cars that are nearest to each other. SEE THE DRAWING.

8) Drill and countersink holes, just as in the cars, 3/8” in from the edges of the 8’ x 14” x ¾” particle board (with laminate) or Melamine. These holes should be spaced about 12” apart and should be drilled and countersunk through the plastic laminate side all the way around all 4 sides of these pieces. Place these pieces so that they are flush to the outside rails and end caps of the frame, covering just half of the inside rails. Screw just one of these pieces down to the frame. This should leave a gap between the two halves of the table top measuring exactly 14” wide. The cars should fit into this gap so that they can slide freely up and down the entire length of the gap from one end of the woodworking jig to the other, resting on the exposed halves of the inner rails that are not covered by the laminated table tops. Be sure the cars can do this before you screw down both pieces of the table top on either side of the gap. You can test this by separating the cars at the turnbuckle, placing them on the extreme, opposite ends of the gap and then using just two screws to hold the second table top piece in place. After the two trial  screws are in, try sliding the cars up and down the track and keep adjusting the second half of the table top until the cars slide freely (but not loosely) up and down the entire length of the gap. Then screw down the second half of the table top to the frame, using all screw holes. Re-attach the cars together, as before, using the turnbuckle.

9) Place the cars aside for now and place the entire woodworking jig assembly on the work bench, upside down. Drill two, vertical, 5/16” wide by 2” deep holes with a Forstner bit into one of the end caps, near the ends of that end cap but about 3” away from the joints with the outside rails. These holes should be 2” deep, exactly. Using the vise and hacksaw, cut the hex head off the two 3/8” lag screws right where the heads meet the shafts. Discard the heads and sand the hacksaw marks off the cut ends of the lag screws, leaving them flat. As before, sand bevels around the outside edges of the ends you just sanded flat. Screw the lag screws (pins) into the holes you drilled in the end caps using Vise-Grip pliers. The pins should protrude 1” from the bottom edge of the end cap. These pins will point downwards when the table is right side up and will drop into two locator holes you will be drilling vertically through the front table of your edge sander. Alternatively, you can use two, large C-clamps to secure the jig to the front table of the edge sander, deleting the pins. However, the pins make it fast and easy to accurately and repeatedly locate the jig at the proper place on the edge sander’s front table.

10) Move the front table of the edge sander so that it is flat and just above the bottom edge of the sanding belt. Lock it in place. Carefully measure the distance between the top of the front table and the floor beneath it. You will now be using the remaining 2 x 3 x 8’ wood to make (2) legs and (2) legs supports, as shown in the plan. The length of the legs must be such that the jig will be level when placed onto the edge sander’s front table. This means that the distance from the bottoms of the outside rails to the floor must equal the distance between the top of the edge sander’s front table and the floor below. See the plan for how and where the legs are to be placed and bolt them onto the insides of the outside rails using the 3/8” x 4” hex head bolts, nuts and washers, one bolt per leg, as shown. The legs should rotate up and down but not loosely. With the jig still upside down on the work bench, place the legs at a 90 degree angle to the outside rails and then make leg supports, as shown in the plan and bolt them to the outsides of the legs and the insides of the outside rails using the 5/16” x 4” hex head bolts, washers and nuts.

11) Turn the jig right side up and place it onto the front table of the edge sander so that the end cap nearest the sanding belt is about ¼” to ½” from the belt and parallel to it. No part of the jig should ever touch the sanding belt. The jig should be located so that it is centered on the sanding belt from left to right. Re-check to see that the end cap is still parallel to the sanding belt and 14” to ½” from it. With a pencil, carefully draw tight circles around where the pins you made from lag screws touch the table. Move the jig back away from the penciled circles and, using a 3/8” Forstner bit,  carefully drill two, 3/8” holes vertically down into the front table of the edge sander. If the front table is made out of metal, you will have to drill ¼” pilot holes in the exact centers of the penciled circles and then drill them out to 3/8” using high-speed drill bits. See if the pins you made will drop into the holes you just drilled. If not, drill the holes slightly larger, in small drill diameter increments until the pins just drop through.

12) You are now ready to sand the edge of your first round table top. Your glue-up should be previously sanded flat in a wide belt sander or drum sander. You can have this done at any large woodworking shop if you do not own a wide belt or drum sander yourself. In case of very wide table tops, I glue them up into 2 or three rectangular glue-ups that will each fit through the wide belt or drum sander I plan on using and then glue those pieces together after they have been sanded. Be sure to use a biscuit or Domino joiner along all glue joints so that the pieces will stay together horizontally and line up as vertically as possible when you clamp them together. Be careful not to place the biscuits or Domino tenons where they have any chance of intersecting the round edge of the table top, as you definitely do not want them to be visible in the final product. All biscuits or tenons should be located safely inside the circle made by the outside edge of the table top. If you are pre-sanding and then gluing up 2 or 3 rectangular pieces into one, square glue-up then you will probably have some height inequities along those seams, even if you use a biscuit or Domino joiner. You will have to carefully sand out these inequities using a random orbital sander after the glue is dry. Your glue-up should be now random orbit sanded flat on both sides and approximately square in shape.

13) Place the glue-up upside down (best looking side down) on some towels on the work bench. Draw pencil lines from the diagonally opposite corners of the square glue up to locate the exact center of the glue-up on what will become the bottom side of the table top. Using a ½” Forstner bit, drill a hole at least ½” deep (the depth of the pivot pin or a bit more) vertically into the center mark where the diagonal pencil lines cross.  Using trammel points clamped on a straight stick, locate the point of one trammel point in the exact center of the hole you just drilled. A pencil should be clamped in the other trammel point. The distance between the trammel points should be the radius (1/2 the diameter) of the table top you intend to create. Draw the circle indicating the final diameter of the table top. Alternatively, you can make a compass by cutting off another ½ bolt, cutting it to length and sanding it and beveling the end so that it protrudes ½’ out of a ½” hole drilled in one end of a straight stick with a pencil sticking through and jammed in a hole at the other end of the stick located at the correct radius from the middle of the center pivot pin. You can drill multiple pencil holes in the same stick for different radiuses.

14) After the circle is drawn, use a jig saw (sabre saw) to cut all around 1/4” outside of the pencil line, leaving a rough table top slightly larger than the final product. Place the cars in the slot down the middle of the woodworking jig with Car B closest to the sanding belt. Rotate the turnbuckle until the two cars are as close together as the turnbuckle and threaded rods will allow and then run it back a few turns in the opposite direction. Slide the cars until the center of the pivot pin is located ½” more than the radius of the rough table top from the sanding belt. Screw Car A in position on the track using the six screw holes drilled into the opposite edges of the car. Place the rough table top right side up with the pivot pin inside the pivot hole on the bottom of the table top. At this point, the rough table top edge should be ½” away from the sanding belt. With the sander turned off, rotate the table top once around so that you can be sure that it is not touching the sanding belt at any point. If it is, back it off with the turnbuckle. Turn on the edge sander. While rotating the table top AGAINST the direction of the sanding belt, NOT WITH IT. Now, slowly turn the turnbuckle until the edge of the table top just starts to touch the sanding belt. Maintain control of the table top at all times as you turn it around the pivot point. Do not let it get away from you. If it does get away and starts to spin, STOP THE EDGE SANDER IMMEDIATELY! Rotate the table one or more full turns until you feel little or no resistance at the contact point with the belt. Hang onto the table edge with one hand and check underneath the table top to see how close you are to the penciled circle marked by the trammel points or compass. Adjust the turnbuckle, pushing the table top slightly closer to the belt while hanging onto the edge of the table top. Rotate the table top again until the resistance stops. Repeat the steps above until the pencil line is just touched or sanded away. Turn off the edge sander and do not release control of the table top until the belt has come to a standstill. Remove the perfectly round table top from the jig and rout or sand the sharp edges until you have the final profile you desire. On a 1 ½” to 2” thick table top, I use a ½” round-over ball bearing router bit all around the upper and lower edges. On a ¾” table top, I use a ¼” ball bearing round-over bit in the same way. I like the simple look and feel of this. You don’t want a sharp edge where people are going to be placing their hands and abdomens.