|Project by Mark||posted 01-05-2011 01:45 AM||7541 views||15 times favorited||11 comments|
I built this jig to work with a Freud SBox8 box joint blade set on the table saw. Borrowed ideas from a number of other LJer’s projects, and added some twists of my own. What’s different? Well, since this blade set is “reversible” to cut 1/4 or 3/8 slots, I decided to make a “reversible” jig that would hold settings for both of those designs, and minimize any need for readjustments.
The finished jig (photo 1) is symmetrical front-to-back, so it can be reversed and fed from front or back. I use it in one direction for 1/4” joints, the other for 3/8”. That way the zero-clearance slot in the sled base and the index pin size and position stays correct for each.
The sled base is 18” x 11” MDF with oak runners, one adjustable to take out all side-to-side play. For the upright part of the jig (photo 2) I just ripped a 3” strip of MDF, cut 18” lengths for the front and back, and cut 12 little 3” squares to laminat into support blocks. Before gluing up the assembly, I routed dual T-slots in the front and back to hold the faces, zero-clearance backup, indexing piece, and microadjustment reference.
I ran out of special metal T-slot nuts, so I ripped some hardwood into the appropriate shape to fit the slot (photo 3) then drilled and tapped holes (photo 4) and finally cut the strip into 1” pieces. Presto – 16 T-slot nuts for free. They won’t last as long as metal, but neither will I…
The facings for the upright were cut from some surplus birch hardwood flooring strips. I tried to show the various components in photo 5. “A” is the microadjustment reference. It is drilled and tapped for a 10-32 thumbscrew with wingnut to lock it. I keep this reference flush with the side of the upright and never move it. “B” is the indexing piece – it has a slot cut and the index pin glued in. To microadjust, you just loosen the screws that hold the indexing piece in place, tweak the thumbscrew on the microadjustment reference, and slide the indexing piece back against it before tightening the T-slot screws.
The zero-clearance backup piece (C in photo 5) can also be reversed, so it can handle two different finger heights (which should be just a little more than the thickness of the stock being jointed). The upper part of the upright holds a backing board (D) to provide enough vertical support and a safe place for my fingers to clamp the workpiece against the jig.
Picture 6 is my first test joint. Worked great! If anyone wants more details and I haven’t bored you to tears yet, I’m happy to share more. Happy new year to all!