The few times I have cut lock miters with my tabled router setup, I have trouble dialing in the bit height. I waste too much scrap doing it.
I went to a great site called “woodshop demos: where the author and demonstrator shows his method.
He takes two pieces of same-thickness stock as that to be worked, labels one “A” and the other “B,” placing the labels on one face only. He adjusts his bit height by eye to align its Z center to the marked center of the stock, then cuts “A” with its labeled face up, and “B” with its labeled face down.
A mate-up is tried, “A” into “B,” and if the A part is high and proud, the router bit is raised by half the distance of the sit-up. He claims it only takes a couple tries to get it right. If the joint goes the other way, with A mating deep, the bit is lowered by half the distance of the offset.
Then, with the bit height set, he cuts the work parts with three passes, moving the fence in toward the bit to deepen the cut each time.
How do you do it?
Replies
Gene,
I love lock mitre joints, especially in plywood as it hides a lot of the edges. Also, they are immensely strong, if you orient their lock aspect to handle the major racking or other forces that the furniture will be subject to.
Trial and error (using something like, but not as scientific, as the method you describe) has been my way. But I've snaffled your posting into my little book of "how to" now. :-)
If you typically use one or more customary thicknesses of stock (eg as with plywoods) then keep templates of your succesful lock mitre cuts with that stock-thickness. These templates need only be a couple of square inches each with one edge of each having the horizontal and vertical cutter profiles. (Cut them on bigger bits of wood when you make them, mind).
Next time you come to lock-mitre that stock thickness, use the templates to set the bit height and projection in your router table.
Even if you use stock that is a bit thicker or thinner, the nearest-size templates are a good starting point and you can often estimate the necessary further adjustments to cutter height and projection "right first time".
Lataxe
The A/B method is what I've been using all along. That bit used to drive me crazy till I figured out that trick. Another TIP for doing the vertical member. Run an extra horizontal piece and rip off the stepped ledges and double side tape it to the outfeed side of the table. This gives support to the piece being fed vertically. Running on the sharp edge is a bummer.
I Also Stack two feather boards horizontally above the cutter, spaced 1" appart to keep the vertical piece from tipping. This is an extra wide featherboard ( 14" ) so I end up with 6" of equal pressure on both sides of the bit.
I also run an extra wide vertical piece so there is plenty of base support, then rip off what I need, leaving room for the jointer.
Work Safe, Count to 10 when your done for the day !!
Bruce S. Counter Sales, Tech Rep. http://WWW.EAGLEAMERICA.COM
Edited 3/29/2006 9:46 am ET by BruceS
This forum post is now archived. Commenting has been disabled