Replies

1. 
   BG | Jan 19, 2007 01:29pm | #1

   Jeff,

   Incra runners...buy the longest you can

2. 
   JohnWW | Jan 19, 2007 06:01pm | #2

   Use the corner of a cabinet scraper.

   John White, Shop Manager, Fine Woodworking Magazine

3. 
   hammer1 | Jan 19, 2007 06:28pm | #3

   Wood runners will shrink and swell with humidity changes. You will always be messing with them. A small rabbet plane or the corner of a card scraper works well for fitting but the runners will keep changing. Sorry to say, you are beating a dead horse. The Incra sliders are easy to mount and they will be accurate season to season. You can reuse them for future jigs and in some cases, you only need one on the fixture.

   Beat it to fit / Paint it to match

1. 
   jeff100 | Jan 19, 2007 06:42pm | #4

   Card scraper...brilliant. I should have thought of that. This is why I'm the amateur and you all are the pros. But I agree, the metal incra runners are the real answer. I should have realized that as well. Guess I was trying to be too cheap....Thanks to both of you.

4. 
   Rich14 | Jan 19, 2007 10:22pm | #5

   jeff,

   You can build a crosscut sled with wooden runners that will remain perfectly aligned to the saw's miter slots, despite temperature and humidity changes. The sled will never bind or become sloppy. I have taught this method and posted it here several times. Here's how to do it.

   It is not possible or desireable to have both runners contact both sides of their miter slots. It is hard enough to machine 4 surfaces in perfect contact using metal working methods. It is impossible with woodworking tools and materials. Besides, if you could actually accomplish this, the result is exactly what causes problems - if the humidity icreases, the runners bind. If humidity decreases, the runners are sloppy in their slots.

   You will construct the sled so that the runners are significantly more narrow than the slots. The inner walls of the runners will contact the miter slot walls closest to the blade. Or the outer walls of the runners will contact the opposite miter slot walls. But not both. I prefer the first situation, but it makes no difference. Only 2 surfaces in contact, not 4.

   Some terminology: The rear fence of the sled is the one closest to you. The front fence is the one furthest from you.

   You will construct the sled in two halves. Select the sled body material, either plywood or MDF and cut it in half. Mill 2 runners from your hardwood of choice, slightly more narrow than the miter slots. Attach a runner to the underside of the left hand side of the sled. I usually rout a dado into the sled for the runner and glue it in place. Or you can just screw and glue it in place. It doesn't matter. Great accuracy is not necessary at this point - that will come later - but make the runner as close as possible to square in its direction of travel. The only critical placement at this point is to position the runner so that the right hand edge of this left side of the sled overlaps the blade position.

   Attach a runner to the underside of the right side of the sled so that the left hand edge of this sled half overlaps the blade position.

   When the glue has hardened on the runners, place the left hand sled half in its miter slot, and, while firmly pressing the sled to the right against the miter slot, saw off the overlapping right edge.

   Place the right hand sled half in its miter slot, and, while firmly pressing the sled to the left against the miter slot, saw off the overlapping left edge.

   Both halves of the sled can now sit in their miter slots, and there will be a kerf between them exactly as wide as the blade.

   Prepare both front and rear fences. Lower the blade completely below the saw table.

   Using 2 bar clamps, clamp the outer edges of the sled at the front and back so that the kerf closes slightly and the runners contact their respective miter slot walls. Clamp gently. Too little pressure and the runners will be sloppy in their slots. Too much, and the runners will bind and the sled will not move. It will not take too much to cause binding. The proper clamping pressure is just enough so that the sled rides snuggly but smoothly. The runners will now be perfectly aligned with their miter slots.

   Move the sled forward, clamps in place, and position the front fence in place and drill and countersink at least 3 holes up through each sled half into the underside of the fence. Tighten the screws in place. Don't glue (yet).

   Move the fence back toward you, put the rear fence in place. Drill and countersink only 2 holes, one at each end of the fence up through the sled halves into the underside of the fence. Elongate the right hole slightly in the front-rear direction. Screw the fence in place.

   Move the sled forward, clamps in place, remove the screws from the front fence. Apply glue to the top of the sled halves along the fence position and re-screw it into place. Check that the sled moves properly as you tighten the screws. Readjust the clamps during this process to keep the sliding action smooth and precise.

   Let the glue dry. Move the sled back, clamps in place. Loosen the right screw slightly and adjust the rear fence with a framing square so that it is square to the kerf. (You must be absolutely certain that the square is acutally square. I can tell you how to test for that if you want.)

   Hold the square against the left side of the fence, with its base pointing to the left and its arm lined up with the left side of the kerf. Then flip the square, keeping the base against the fence so that the base is pointing to the right and line the arm up with the same left edge of the kerf. The fence will be square to the kerf when the arm of the square lines up with the left kerf edge, with the base in both positions.

   (Afterwards, there are methods to test that the sled is cutting square. I'll leave that for later).

   With the rear fence square to the kerf, tighten the right screw. Drill several more holes up through the sled into the fence. Tighten the screws in the left hand holes. Remove the right hand screw, put glue under the fence, tighten all the right hand screws. The clamps are still in place. Adjust them as necessary to keep the sled running smooth and precise during the gluing and screwing of the right side.

   When the glue has set, glue and screw the left side of the fence, adjusting the clamps as before for true-running. Let the glue set. remove the clamps. Attach a block to the rear fence where the blade will come through. Saw through the front and rear fences. Sand your sled and give it a couple of thin coats of shellac. Sand the first coat to level the raised grain. Wax the runners and the underside. Enjoy.

   Read through these instructions a few times until you can picture the entire process. It seems like a lot, but it is very straight-forward and quite simple. This method is actually one of the easiest ways set up a crosscut sled. In fact, it is really so easy, that once you make one, you may want to make other, specialized versions. Others have. It is certainly one of the most accurate.

   Rich

1. 
   jeff100 | Jan 22, 2007 09:05am | #6

   What you describe makes complete sense. I will cut and paste this into my personal notes for future reference, and use the process to build my sled. I guess I'll have to consider my current effort done, call it a 'test' run and chalk it up to experience....Many..many thanks Rich.