|Project by Mark Whitsitt||posted 01-18-2011 06:01 AM||9036 views||87 times favorited||17 comments|
Well, it seems like all I’m posting is jigs and fixtures… that’ll change soon!
This one is a bevel sled that I made specifically for the next project I'm going to post. I didn’t want to have to keep changing the bevel of my table saw blade back and forth, so I decided to make a jig that would give me good 45 deg bevels with a vertical blade.
You can see the design in the pictures, which is pretty straight forward; here’s what I found are the keys to the jig:
1. Use 1/4” or 1/2” material for the base of the sled. 3/4” plywood took up too much blade for thicker work pieces.
2. make the platens as close to 45 deg to the blade as possible, but more importantly, make them exactly 90 deg to each other. If you cut all the right side workpiece bevels on the right side of the sled, and all the left side workpiece bevels on the left side of the sled, you’ll have a perfect bevel/miter joint, even if the blade is slightly off vertical. I mark all the corners of the workpieces with an R or an L so I know what I’m going to do.
3. My first version didn’t have the clamps on the faces of the platens and I tried to use F-clamps to hold the workpiece to the jig… not good enough… but you absolutely MUST clamp the workpiece to the platens to keep it from falling into the blade as you push it past the blade. That will severely screw up your bevel matching!
4. You have to cut the bevels with the workpiece FACE DOWN! This caused a little difficulty in my next project posting about golden boxes.
5. You’ll have to experiment a little bit, but I have to cut the workpiece blanks (unbeveled) about 3/16 long to account for the kerf created by the blade if I’m trying to make something to a specific dimension. Otherwise, as long as you’re cutting all your sides with the same jig, and you don’t care what the exact final dimension is, just cut the opposite sides of your box to the same rough length and you’ll have a systematic difference that will allow them all to line up perfectly.
Other bits: I’m using shop-made QSRO runners in both miter tracks; I use the opposite platen and a back fence to register the workpiece with the blade, and took a little work to get the fences satisfactorily perpendicular to the blade.
My next project post has examples of work created using this jig, as well as my Golden ratio dividers.
-- -- "there are many good reasons to use old hand tools, but moral superiority is NOT one of them..."