 |
|
|
In the ShopMaking a Miter Jack
I was making an end table with triple miter joints and could not see how I would be able to get the joints fitted perfectly without a miter jack to help me plane them at exactly 45 degrees. Tony Seo posted a link to an online auction which showed a type of miter jack which was new to me. It looked intriguing and less complicated to make than the traditional open design. I decided it would be nice to have one of these to help make these joints. The one I am making in this description is actually the second one I have made; I did not document the first one. I had some left over 8/4 and 4/4 hard maple that I thought would be good for this. I wanted the miter jack to be wide enough to take stock that was at least 3" in each dimension. I glued up two pieces of 8/4 hard maple, so I would have 3 1/2" thickness, and planed it to square it up. It is important that each edge be made as close as possible to 90 degrees. This piece of wood is about 3 1/2" by 3 1/2" by 9 inches long.
Here are all the parts used to make the miter jack after dimensioning. The main center block is the big rectangular prism, the sides are the two 4/4 boards behind. The sides should be exactly the same height as the center block and about 6 inches longer. The rails are the two 1/4" x 5/8" strips. Four rails, each the length of the center block, are needed. The screw will be made from the 1x1 piece of maple in the foreground. One piece, the end block, is not shown. Another miter jack is just on the left edge of the picture. This miter jack is too small to use for the current project, being only big enough for 2" stock, so I am making a bigger one.
Using a Stanley 45 to plow grooves in the sides of the miter jack for the rails. The central block will also have grooves. The rails are glued into grooves in the central block and slide in the grooves on the sides. Take very special care to make sure that the grooves are parallel to the sides and don't veer off at the end of the board. If they aren't really straight, you may need to use a Stanley #79 or equivalent to straighten them up (DAMHIKT!).
Here the rails are being glued into the grooves that were plowed in the center block of the miter jack. The sides are in the foreground with the grooves shown. It is worth taking extra care to make sure that the grooves are *really* parallel to the edges. Even so, the rails might require some trimming to get a good fit between them and the sides.
Using my trusty MF miter box to saw the miter jack center block at 45 degrees. One set of rails has been planed to make sure that there is a right angle when a square is placed across the rails and up one side. This set of rails is placed down on the miter box bed and the side is placed against the miter box back fence. This ensures that the block will be cut square with the 45 degree face. If the block is not cut squarely, it will not make a very good miter jack.
Here the sides and end piece are fitted to the center block. The end piece of the center block will be glued between the sides. The near section will slide on the rails. The near end block will be drilled and tapped for a wooden screw. It could be fastened in place with dovetails, but I took the easy route and pinned it with dowels.
The only screw box and tap that I have is for making a 3/4" screw. Here I am drilling a 5/8" hole that will be tapped for the screw. I've put a small square on the piece so that I can get close to drilling it straight through.
Tapping the end block.
Using my Woodcraft screwbox to thread the 3/4" screw. One step has been omitted to protect the innocent since some electrons were sacrificed when turning the 1x1 piece into a 3/4" dowel. You can see the miter jack in the foreground with the dowel pins holding the end block in place.
Here it is assembled. The screw pushes the moving block against the fixed block at the far end. After assembly, check the accuracy of the 45 degree angle to the top face and adjust by planing the top surface. You can see the dowel pins used to attach the end block to the sides.
Here is the smaller miter jack in use. The miter jack is clamped in my face vise and a stretcher is inserted from the bottom. The screw is used to clamp the stretcher in the 45 degree slot. The stretcher is show proud of the surface here, but in use it would be almost flush with the surface. A shoulder plane is used to trim the mitered surface right up to the tenon.
Here is a picture of the end table that I made. The triple miter joints can be seen at the top of the leg and where the stretcher joins the leg at the bottom of the drawer.
I have never used one of the more traditional types of miter jack, but this one works well and it is nice that it clamps the piece securely so that a very accurate miter can be planed. I like the fact that it is easy to fix in the face vise and that it was not too hard to make. Best Regards, February, 2006 |
||
|
|
 |
