Ideal router bit for cutting dado in walnut

[Dan Borello]

I am looking to cut several 3/8" deep, ~3/4" wide dados in walnut. I have a Freud spiral upcut bit, but the tearout is pretty bad.

What bit would you recommend for cutting dados with the router? There was a similar thread a few years back, but it was coupled with other issues, so I thought I would get an update opinion.

[Jamie Buxton]

Boy, something is not right. Walnut usually machines very nicely. A regular straight bit, or an upcut spiral, should not give you tearout. Maybe the bit is dull.

[pat warner]

Down cut, same config. = 0 surface tears.
But take it easy, with a new cutter you can waste 3/16"/pass.

[glenn bradley]

Pat's got it but, no surprise there ;-)

[Peter Quinn]

You are better off with a regular two wing straight bit or two flute shear cutter than an upcut spiral. Upcut is for mortising, it pulls chips up out of deep mortises, but leaves a poor surface quality because it pulls chips up, including the surface of your board! I'd try any other bit you have as a test, most likely an improvement.

[Mike Cutler]

I personally would use a 1/2" down spiral bit, or a 1/2 straight with bottom cutters, and do it in multiple passes.

I've used spiral upcuts for grooves before, and the tearout wasn't what I would call "pretty bad". Is your bit sharp?, what diameter? and how much material are you trying to remove in a single pass?

[Grant Wilkinson]

Are you cutting these on a table mounted router or a hand held?

[Jim German]

If you've got a big CNC router with a 3/4" collet Whiteside has a 3/4" solid carbide down cut spiral bit that would be 'Ideal'. If you've got a regular router, either a 1/2" downcut spiral but or straight bit should work well.

[Dan Borello]

Boy, something is not right. Walnut usually machines very nicely. A regular straight bit, or an upcut spiral, should not give you tearout. Maybe the bit is dull.

I should have been more clear. I was using the 1/2" upcut on BB plywood and got pretty bad tearout. Therefore, I figured for my more serious project (Walnut), I should grab a new bit.

[Dan Borello]

Grant, I am using a table mounted router.

Jim, Unfortunately it is a regular router.

It sounds like a 1/2" downcut spiral or straight bit is the way to go. Any particular bits? Otherwise, I generally go Freud.

[Mel Fulks]

Single flute bit cuts much faster than two flute. Hard to find in retail stores but easy to order.

[Bruce Wrenn]

Reverse Helix screw on cutter from Her-Saf. I use 1/2" one to cut dadoes in birch plywood, with no tear out. You will have to buy arbor, plus cutter. These were designed for melamine board, but work great in other applications.

[mreza Salav]

BB ply is nowhere near Walnut, if you are cutting the dado cross the grain you get more tear out but if you use a downcut (as suggested) there should be almost none.

[Rick Lizek]

Reverse Helix screw on cutter from Her-Saf. I use 1/2" one to cut dadoes in birch plywood, with no tear out. You will have to buy arbor, plus cutter. These were designed for melamine board, but work great in other applications.

Hersaf is out of business.

[Bruce Wrenn]

Hersaf is out of business.Tell me it ain't so!

[Rick Lizek]

Out of business for over a year. Southeast tool is making some of the bits now.

[Robert Engel]

Scribe lines with a marking knife before cutting this will avoid tear out.

Anything but an upcut bit ;) will work.

[glenn bradley]

Any particular bits? Otherwise, I generally go Freud.

I am a Freud fan but, for router bits in general I go to Whiteside due to their quick and inexpensive sharpening. Once I get a half a dozen bits or so that are beyond my ability to touch up, I stick them in a flat rate box and away they go.

[Rick Moyer]

I don't do a lot of router work but I do love the Whiteside bits I have.

[Dan Forman]

Keep in mind that what is up cut in a hand held router becomes down cut in a table, and buy accordingly.

Dan

[Allan Speers]

Keep in mind that what is up cut in a hand held router becomes down cut in a table, and buy accordingly.

Dan


That's not right, is it?

On a table, the stock is above the bit, so flute orientation is the same as hand-held. No?

[Art Mann]

Allan, you are correct. If you want to use a downcut bit to cut dados, you use the same downcut bit whether you put it in a handheld router or a table router. I am not sure what Dan means.

[Art Mann]

Single flute bit cuts much faster than two flute. Hard to find in retail stores but easy to order.

Sorry to disagree. There are several reasons to use a single flute bit but cutting speed is not one of them. I use single flute bits, 2 flute and occasionally 3 flute bits on my CNC router. You can run the X and Y speeds much faster with multiple flute bits.I would not recommend a single flute bit at all for the original poster's needs.

[Mel Fulks]

Art, you don't say they don't cut faster ,just that speed is not a reason to use them. Op is looking for speed...and they do cut faster. She does not have a CNC router but probably understands they are different and that the bits sold for them are made for them. As I pointed out the other day the manufacturers say they cut faster. If you know of one that says they cut at same speed or slower please tell us what brand they are so that we can avoid them. Thanks.

[Art Mann]

Pardon me if I was unclear. Let me try again. I am quite certain that a 2 or 3 flute router bit will cut much faster than a single flute bit of the same cutting diameter. I have proven this time and again with a machine that will cut at a precise speed, which takes the flaws of human perception out of the equation. I suppose you could force a single flute bit through a piece of wood at the same speed as a 2 or 3 flute bit but the cut quality would be awful. This principle holds true whether it is a CNC router, table router or handheld router. What allows a higher travel speed while maintaining cut quality is the number of cuts per inch. It is obvious that a multi flute bit will provide more cuts per inch than a single flute bit. I don't know where you got your information but I don't know any other router users, or bit manufacturers for that matter, would agree with it.

If you get interested, you can go to a bit manufacturer's website, like Onsrud for example, and read up on the concept of chip load. This mathematical concept allows you to actually calculate the correct speed for a bit of a particular diameter and flute geometry bit. You can even download a table that allows you to just look it up.

[pat warner]

Might be that there is more to the story. Cut quality & inventory for example.

Single flute bits, whilst usually with more web, on occasion, are stiffer and can handle more aggression (cut volume and speed), but they're naturally unbalanced. As such (the inventory issue) there are very few flute designs and almost none with shanks >.500". Moreover, they chatter and often spin with resonance (a don't-want).

And the same can be said of multifluted bits. 2 identical flutes on the same shank are well balanced tools, the best compromise for wear, stiffness, balance, economy and cut quality. Add more flutes (on straight bits) and the stiffness diminishes and the chatter increases.

As the shanks get bigger, however, the modulus (stiffness) increases substantially. Start adding more flutes (for .5" shanks and less) and generally you add money, thin webs, short life and chatter.

Cut quality paramount? Then stick with solid carbide, 2 flute cutters.
Accept >.500" shanks (CNC), plenty of HP, lots of flywheel? Then multifluted bits are for you. And impeccable finishes are to be expected.

And as an aside. I have a 5 flute down spiral, solid carbide .500" CD, finish end mill cutter.The best tool I've ever used for aluminum, plastic and wood. Stiff as any 2 flute tool, leaves a finish like no other, running at 22,000RPM.
Safe? I don't know, nor do I know how long it lasts. Still experimenting.

[Brian Holcombe]

Scribe lines with a marking knife before cutting this will avoid tear out.


This^

Highly recommended

[Mel Fulks]

Mr. Mann: You are certainly out talking me and yet unwilling to read my brief replies. I don't need to get interested,been involved in the subject for a long time. I found and noted a site for cite. And included it in post. Op is interested in quick way to cut plywood perimeter. I have just noticed that I have confused two similar threads with same solution ,sorry. But same bit works in both cases.

[Lou Ortiz]

Not to be contrarian, but i think the whole uncut/downcut thing is relative to the surface of the material, not the orientation of the router.

[Robert Engel]

Keep in mind that what is up cut in a hand held router becomes down cut in a table, and buy accordingly.

DanSince the relationship of the wood to the router is the same, so there is no difference.

[Dan Forman]

Sorry for the confusion, just repeating something I had been told when I was looking into buying a bit for similar purpose. I never did pull the trigger, so didn't have the opportunity to check it out. I don't have much in the way of spatial skills... :).

Dan