I need to cut about 200 or so biscuit slots for a set of bookcases, using my PC plate joiner. First time I have used the joiner and noticed it jumps around so I built a jig to hold the joiner securely in place against a fence. The jig is a modifed, striped down version of one shown in a magazine, I think Better Homes and Garden 101 Best Shop Jigs Ever. The plan called for a plywood base with a 1/8 inch masonite top, T-slots, hold-downs, the works. Mine is just 3/4” MDF thrown together. But it’s sturdy and square. Here it is. Oops, the corner of the photo got cut off on Photobucket.
Anyways, it measures about 24”x14” with a 6” gap for the joiner. The fence is 1.5” tall. The plan called for a slightly larger base, but this is all the MDF I had, that I wanted to dedicate to this jig. The 6” gap is per the plans. Since my PC model was shown in the plans, I think a 557, (I’m not a model number snob because I’m old and can’t remember very well), I figured the gap width was good to go. There is about 3/16” or so play on each side of the joiner as it rests in the gap. There are also two 1”x6” cleats, or stops, set 6” from the back edge to hold the jig parallel to the workbench and to keep it from sliding around. I use a clamp to hold it securely to the bench. The pressure is towards the bench so one clamp is good enough.
I just used brads and glue to assemble the jig. The trick is to keep the parts on each side of the slot square to each other because the fence will reference off these pieces. It’s also good to keep the cleats square but not as critical.
I tried it out and noticed the joiner can jump around even in the slot. You need to have a good grip on the joiner and the material you’re cutting. I didn’t want to fuss around trying to concentrate on holding everything in place so I affixed the joiner to the jig. I looked at the two holds provided in the base of the joiner and assumed they were 1/4”. They sure looked like 1/4”, lol. So I set the joiner face plate against a piece of stock held tight against the fence and marked the holes in the base of the jig. I turned the jig over, marked the hole locations, and drilled two 1/4” deep holes using a forstner bit thinking I would use 1/4” bolts. The forstner holes were oversized to accommodate a socket. I went to the borg and bought the 1/4”x2” bolts, nuts, washers, etc, got them home and realized the holes are just slightly smaller than 1/4”. DOH. Bad enginering if you ask me. Why make the holes just a shade under 1’4” So I ended up using #10 machine screws, the next smallest screw I could find. I thought they were a little to small to hold the joiner firmly but they actually work fine. The joiner ain’t going nowhere. I will know immediately if it rides out of square.
I bought the joiner used, gently used. I doubt the guy cut 10 slots with it. I cut some slots for a 0 size biscuit and noticed the slots were too deep by maybe 3/32”, and were off vertically from center of board by a fat 1/16th. So I made some adjustment using the hex screw on the depth adjustment knob, which had never been cracked, and fine tuned the height of the blade using the rack and pinion adjuster. I made a few cuts on 3/4” hardwood plywood just to make sure and it is dead nuts. I now kown the previous owner never made the adjustments and was probably frustrated using it. Maybe so, maybe no. Here is a photo of the depth adjustment knob, and you may can see one of the #10s I used. Actually the #10 is slighty cut off in the bottom right of the photo.
So now no more excuses.
-- Better woodworking through old hand tools.