Where to find a router bit

[Greg Guarino]

I made this router dado jig for an upcoming project. It's my third iteration of this jig and hopefully my last. (The first, made ten years ago, was crude but reasonably effective, the second was better but got damaged in a flood).

I have a flush-trim bit that is 1/2" in diameter with a 1/4" depth of cut and a 1/4" shaft. That works, but I'd like to at least have the option of a deeper dado. Ideally it would be 1/2" in diameter with a 3/8" depth of cut. I can't seem to find such a thing. I saw some much deeper bits, but I feel like I might get clumsy someday and more easily damage the "runners" of the jig. Any ideas?

[Just Wondering]

It sounds like you're looking for something like this: BOSCH 1/2 In. x 1/4 In. Top Bearing Dado Clean Out Bit

Changing the subject, I recommend you spring for a router that uses 1/2" shanks like these:

(This one is a 1/2" dia. 1 1/4" deep double-fluted straight bit.)

If you cut dados frequently, you could get a stacked dado table saw blade set.

the price of four router bits you get the ability to cut dados from

1/4" to 13/16" in 1/32" increments.

[Greg Guarino]

That's pretty much exactly the bit I have. I was hoping for one that cuts a little deeper. I have a router that has a 1/2" collet also, but I wondered if the shaft would rub on the "runners" of the jig, being the same diameter as the cutter.

[krw]

Instead of a trim bit, why not a bushing and up-spiral bit.

- Make a wider dado through the top half of your jig (or add another layer. It really doesn't matter how wide the dado is just wider than the bushing and centered.

- Slide the left and right pieces (so the bottom of the jig touches).

- Use the router bit with the bushing to cut all the way through the jig.

- You can now use the bottom half you your jig to reference the thickness of your board. The top of the slot is the difference between the bushing and bit.

Just run the bushing along the top edge of the jig and your dado is the width of your reference. You can expose as much of the bit as you want past the bottom edge of your jig.

It's kinda like a shooting board crossed with a Kerf Master for a router. Use the same bushing and bit and there is no further calibration needed. The minimum dado width will be your bit diameter, obviously.

[Greg Guarino]

I had to read that a couple of times before I could imagine it. My solid wood "runners" are only about 1/4" wide. Unless I have a bushing that is really close to the size of the bit I'm going go all the way through the "runner".

Another issue I can imagine is the centering of the bushing. As it stands, the roller on the bit is obviously perfectly centered on the bit. But with a bushing I have to do some fancy alignment, or (I suppose) make sure to keep the router in the same orientation for every cut. I'm going to mull this over a little more.

[Leon]

You can do a deeper dado with that bit. Just make two or more passes. Complete your first cuts then lower the bit. It will use the first cuts as the guide. That is how I do mine.

[Leon]

This works but...... you have to use a guide bushing and it has to be perfectly centered with the bit and or you have to remember to not clock the router when making the cut.

A top bearing bit precisely makes the cut with no adjustments needed for a bushing that might be off center.

[krw]

Exactly. You do that once and your jig is calibrated. Yes, if you put the runner on top, you'd cut the jig you have now. If you use the runner you have now on top, you could put the sacrificial strip on the bottom. It doesn't take much thickness. 1/4" plywood on the bottom of your jig is enough. Replace the plywood to recalibrate.

Use a centering mandrel. It's something that's needed anytime you use bushings.

[krw]

Again, use a centering mandrel.

Not a problem.

[krw]

[Leon]

[krw]

He was afraid of screwing up his fixture if a longer bit slipped. I think he wanted a bit exactly the depth of his dado.

[Greg Guarino]

In the past, partly because it was the bit I had, I made 1/4" deep dados. Which worked fine, but I'd like to at least have the choice to make them 3/8" deep. I'd prefer to do it in one pass. Although I I've never actually done that, so that might be too big a bite all at once.

And yes, I do wonder if there's a greater chance to somehow nick the "runners" when so much of a 3/4" deep cutter is "extra" and microscopically close to the runner. All it would take is a little tilt. Which, granted, shouldn't happen, but it's easy to get distracted.

[Leon]

Remember, once you have the established dado/groove you can make it deeper by using it's sides as the bearing guide.

[Greg Guarino]

Thanks.

[krw]

It sure is. I nicked one of my Festool rails yesterday. The piece shifted (fell off a spacer) and the saw came out of the track. I did it when I first got the saw. On the other rail! I was going to use it for this cut but the tear out strip was peeled back and I was too lazy to put another on. Damn!

[krw]

How do you do that. He's going from 1/4" to 3/8". The cutter length is certainly more than 1/4". The bearing will still be out of the piece. Obviously a bottom bearing isn't going to work.

[Greg Guarino]

I assume he means to do it while the work is still in the jig. The easiest way being with a plunge router so you can repeatedly go back and forth between "first pass" depth and second pass.

[krw]

That's not the way I interpreted it.

"> >Remember, once you have the established dado/groove you can make "> >it deeper by using it's sides as the bearing guide." ^^^^

"it's" references "dado/groove", not the tool, which isn't mentioned in sentence.

Using your interpretation, the dado/groove could be done in one pass.

[Leon]

If the cutter is 1/4" and the dado is 1/4" deep simply plunge 1/8" deeper, then the bearing will ride along the existing 1/4" deep side.