Hi All,
On page 34 of the October 2005 issue of FWW the author explains how to build a jig to rout mortises using guide bushings. Cutting the slot in the jig requires a bit with a diameter equal to the outer diameter of the bushing. So if I want to cut 3/4″ mortise, the bushing is going to be , say, 7/8″ so I need two bits, one 3/4″ and one 7/8″. Right??
Replies
That would be the simplest way, but not the only one. I have made jigs using smaller bits, then filed carefully to the line, and so on. You can invest time in making the jig (instead of money) - it's only that one piece that needs to be done.
Also the mortise itself can be cut with a smaller bit. You could cut a 3/4" mortise with a 1/2" bit for instance. The jig would have to allow for the bushing to move 1/4" to the side as well as the length of travel. It's not ideal, but it's OK, especially if you only have a few to do and don't want to buy the exact size bits.
DR
Being a hobbyist, I'd rather invest time than money. For the current project I don't mind spending time on the jig to speed up since I wil lhave to cut quite a few mortises. I will keep in mind using smaller bits to make the jig.
Yes, you got it, although Ring's explanation would work also.
If it's under 3/4, I use a 3/4 bushing just because I have a 3/4 bit and that makes it easier to cut the guide hole.
Good point. I was trying to match the bushing size to the bit but as long as it fits it does not have to be tight. This will definitively help. Thanks.
If you want to route a 3/4" wide mortise, the template guide has a 1" diameter, I do not see a 7/8" dia. guide on the list.
You do not need a router bit to make the fixture. If you rip a "spacer stick" the width of the template guide's diameter, it can be cut in two, spaced for the mortise's length and glued to the edges of the front and the rear table of the fixture.
If you don't like the thought of a single size/use fixture; use a slot cutter and groove half of the length of both table edges and both sides of one of the ripped strips. Then glue a slip in each side of the ripped "spacer".
The rule of thumb for mortises is 1/3 of the stock's width. So, a 3/4" wide M&T joint is appropriately sized for a stick 2 1/4" wide.
Practice...'till you can do it right the first time.
Thanks for the tip.
I tried this idea and it works great (you were right I used a 1" diameter bushing).
Make the jig on the table saw. Rip a piece the width of the cutout you want in your jig. Cut it in half, and glue the two halves between two boards to complete your jig, with what ever length you want the slot in you mortise jig to be separating them.
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