One straightedge, as long as the bit is the same diameter as the dado,
*IF* you can keep the router base perfectly tight against it. That's not what he was suggesting though. The technique Mike suggested is interesting but I see the one flaw. I'm asking questions because I like the idea (two straightedges and a "calibrated" block) but want to understand the limitations.
The only way to eliminate the possibility of a "gotcha" is to use an undersized bit (more than 50% of final dado)and two straight edges straddling the dado. Make a pass each direction cutting first one edge then the other.
Lew
Yes, I understand that (never though of the reference block, though). I guess I'm not being very clear, but near the end of the board, within a base radius, one of the straightedges will be off the end of the board.
And?
Not only is the straight edge extending beyond the board but the cutter is in free air and almost half the router base is still supported by the board.
No harm, no foul.
Lew
Ok, I think I get it now. I'm not talking about using two, while you're making the cut. Just one.
I'm saying you can use two, to help space out multiple, equally spaced dadoes. If you're putting fixed shelves 12" apart, you make a spacer/spacers cut
12". Place first clamp and make first dado cut. Leave first clamp on. Insert spacer/spacers and apply second clamp against spacer. Cut second dado. Leap frog clamps to continue.
No, I'm not talking about a rabbet, rather a dado, say 2" from the edge.
What's the flaw?
Ah, OK, there's the misunderstanding. I thought you were using the second straightedge and block to define the width of the dado. A good idea, except for the edge effect. I like my routers (PC690 w/"D" handle and Bosch Palm) but they're not good at hogging out a 3/4" dados in one pass.
Isn't a rabbet, by definition, at the edge of the stock?
If not, it *is* a dado, no?
If the rabbet is 2" from the edge, it is a dado.... unless you're saying it's a 2" long rabbet..... ...which would probably make it a tenon. :-)
A misunderstanding of your technique? See my 1:00 post.
Cool, we're both seeing oranges, now. :-)
However, I've seen the technique using two clamps to determine the width of a dado, too.
And yeah, you usually want to make a few passes, it they're deep. Using a bit that ejects sawdust rather than just push it, helps too.
Now, we're back to whatever post talked about a tablesaw stacked dado being much better. :-)
IIRC, technically a rabbet is with the grain too, but I could be mistaken.
Read the paragraph again.
No, I said; "I'm *NOT* talking about a rabbet, rather a dado, say 2" from the edge."
Yep. ;-) Sorry for any confusion.
I've built jigs to do this but never thought of using two clamps. Doh!
I just bought an up-spiral bit for use in my table. I'll likely buy a few more over the next few months. Unfortunately we're getting close to the winter no-woodworking season. :-(
Now that I have a table saw, sure. I still tend to use a router for large panels. I'm not very good at controlling sheets of stuff on the table saw. Moving the tool is easier.
Gotcha. brainfart
In any case, and even though it wasn't the original topic, like another guy wrote, a rectangular base allows a router to "hang off" the edge quite a bit farther than a round one.
Yeah, it all depends on your tools and what you're comfortable with. On my last TS, I would never have even considered cutting dadoes, let alone on a full sheet. On my new-to-me TS with the out-feed table I recently completed, I can't wait to try it. :-)
I have a Unisaw with 50" fence with a roller stand for outfeed. I just don't feel comfortable humping something that awkward around alone though.
=A0 =A0Oh, I added a remote on-off switch - that made it perfect.
I did that as well, but with a slight variation. I used a foot switch (HFT $9.99) and a shorting plug. I built in an electrical box with a duplex outlet and a three-way switch. One of the outlets (A) is switched betwen the three-way and the power and the other (B) is wired in series with the other duplex outlet.
The cheap HFT foot switch is plugged into "B" and the shorting plug is plugged into the foot switch. when the three way is in the "up" position, outlet "A" is energized and anything plugged into it gets power.
When the three-way is in the down position, the power to "A" runs through whatever is connected to "B" (the foot switch) and I can start and stop "whatever is plugged into "A" (the outer) using th efoot switch.
Since I did not re-wired the foot switch itself, I can unplug it, removed the shorting plug and plug a tool into it and use it as designed/intended.
This smacks of a "suicide cord"; dangerous as hell.
Which is why another post was talking about a radial arm saw with a dado stack; somewhat scary, of course, but much easier. Small RAS don't have the right guards for a dado, that's a MAJOR reason to buy a big 'un.
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