Making Half Blind Dovetails with Jig
From Zanecorpwiki
Dovetailing is considered the mother of all joins. It's aesthetic and super strong. The half-blind dovetail jig is perhaps the fastest way to create a dovetail join. Without a lot of expensive, dedicated hardware, the setup can be long and the resulting dovetails are often not as tight as with other methods.
Preparing Stock
It's vital that the stock edge be square. For our basic setup, a chop saw is the easiest method to get decent results when possible.
- determine measurements
- plan cuts on board
- most chopsaws rotate on their base, and a compound chopsaw can also make angled vertical cuts, make sure that the chopsaw is square in both axis, use a carpenters square to double check
Single pieces (like the back side of a drawer) should be cut to size. When making two parallel pieces (like the matching sides to a box), cut the first with an extra 1/8th inch. Align the first piece with the edge of the board and position to take off the extra bit as the second piece is cut in parallel. This makes sure the pieces are the same size without triple-checking measurements.
If, when the cuts are made, a small piece of the board is uncut, you can raise the boards on scrap or across other cuts.
Calibrating the Jig
The key to making a decent join is to calibrate the machine properly. The first time this is done, it may take many attempts to get a satisfactory result. With some familiarity, 2-3 attempts should be sufficient. You'll need 1/2-3/4 an inch of board on two stock pieces for each attempt. When using a hardwood, I make my first attempts with similar sized pine stock in order to get the rough calibration without wasting expensive stock.
The key is to square the jig. The first thing is to make sure the combs are parallel. With a half-inch comb, a standard ruler is 1/2 inch wide and will span the peak between two combs. The ruler can be aligned with this and measurement can be taken against stock in the machine. After the combs are aligned, the fence can be aligned by taking measurements against the back of the comb. At this point, the ticks on the fence adjustments on both sides should be more or less lined up.
Routing
When using a universal bushing plate, it's likely that the bushing will not be centered and off-center is potentially doubled; 1/32 off becomes a 1/16 gaps. Ideally, get a bushing set specifically for your router. Otherwise, try and keep the router in roughly the same orientation the entire time you're tracing the comb. Unfortunately, This makes routing more difficult as you can't roll through the curves.
