round nose router bit

[Jim Colombo]

Does anyone know where I can get a 3" diameter round nose router bit?

Thanks,
Jim

[Anthony Whitesell]

MLCS goes up to 2" in the core box bit. You are looking for a 1 1/2" radius 1 1/2" deep bit? That is a huge bit for a router. Even the door panel bits that are 3 1/2" in diameter are only 3/4" thick. (ie., half the mass/weight).

Are you actually trying to make a 3" wide 1 1/2" deep channel in a piece of wood? Maybe there is another way to make the cut.

[Jamie Buxton]

MLCS, and others, have one with a 2 3/4" diameter -- http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bit_molding2.html

If what you want to do is make straight cove molding, there's a tablesaw technique for cutting the cove, and it can be used to make almost any size.

[Anthony Whitesell]

But the cove molding bit has a 2 3/4" diameter, but only a 3/8" cutting height (depth). Whereas a round nose bit usually has a cutting depth equal to its radius.

(I looked for something like this a while back to back grooves for a spice rack)

[John Grace]

Three inches is a lot to do with a router bit...I've never seen one anyways. As Jamie's pointed out, there is a relatively easy table saw technique (see URL below). It's a little scary looking at first blush but isn't all that bad...very, very small cuts. Be advised, while the technique works quite well it can leave some brutal tooling marks. Good luck...John

https://www.youtube.com/watch?v=Qe5ZeSX-_g0

[Jim Colombo]

MLCS goes up to 2" in the core box bit. You are looking for a 1 1/2" radius 1 1/2" deep bit? That is a huge bit for a router. Even the door panel bits that are 3 1/2" in diameter are only 3/4" thick. (ie., half the mass/weight).

Are you actually trying to make a 3" wide 1 1/2" deep channel in a piece of wood? Maybe there is another way to make the cut.

That's exactly what I'm trying to do. The table saw technique won't work because I can't get the depth.

Thanks guys

[Malcolm McLeod]

That's exactly what I'm trying to do. The table saw technique won't work because I can't get the depth.

Thanks guys

Assuming you can get 1-1/2" projection of your TS blade, I think you can get the 3"W x 1 1/2"D channel you want, but result will be parabolic arc, not circular. Assume the parabola is the issue?

Not sure where you're headed, so not sure what alternatives to suggest...?

[Anthony Whitesell]

Assuming you can get 1-1/2" projection of your TS blade, I think you can get the 3"W x 1 1/2"D channel you want, but result will be parabolic arc, not circular. Assume the parabola is the issue?

Not sure where you're headed, so not sure what alternatives to suggest...?

The blade is circular, so I think it comes out circular. Set the blade to 1 1/2" then start rotating the cove guide until you get a 3" width. Pretty good video here http://www.rockler.com/cove-cutting-table-saw-jig

The question then becomes how many liner feet do you need to cut. With a TS blade, you can only remove as much material as you have carbide on your teeth. 1/4" maximum per pass, likely less.

[Malcolm McLeod]

The blade is circular, so I think it comes out circular. ...



If you feed the board perpendicular into the blade, you'll get a circular profile, but its radius will be the same as the blade's radius. To get a 3" diameter circular cut, you'd need a 3" blade.

Hold a 10" diameter TS blade perpendicular to your line-of-sight. It's 10" tall by 10" wide, and circular.

Now start rotating along its vertical axis. Result is that the blade's height stays the same 10", but to your eye, it's 'apparent' width gets smaller as you turn it. It becomes an ellipse. Half of an ellipse is a parabola. Same as with a board being cut along this sight line.

I've also never seen this TS technique used at 90 degrees to the blade, let alone tried it. Perhaps others can weigh in on feasibility??

[Walter Plummer]

Infinity has this one that is 1 3/8" Radius. http://www.infinitytools.com/1_2-Shank-Cove-Crown-Molding-Bit-1-3_4-CD-3_8-CH-1-3_8-R/productinfo/56-602/ . I think you can make close to what you want in sections and glue them up. I think even if you find a 1.5" radius bit, taking that much out of one block of wood is not a good idea. It will probably pinch in or split apart depending on the grain. My two cents, trying to help. Walt

[Davis Young]

This might not result in the accuracy you need, but would it be feasible to use a 3" forstner and possibly a bit extender to drill into a blank and then split the blank?

[Jamie Buxton]

Over in the Neanderthal forum, there's a thread about doing this. http://www.sawmillcreek.org/showthread.php?235751-wood-gutters Lots of work!

[Jim Colombo]

This might not result in the accuracy you need, but would it be feasible to use a 3" forstner and possibly a bit extender to drill into a blank and then split the blank?

This is what I finally ended up doing. I glued 2 2"x3' wide boards together to form a 3"x4" log. Which I cut into 6" lengths. Now I'm in the process of boring each of the 6" sections with a 3" Forstner on the lathe. It's really slow going because I have to let the bit and wood cool down between cuts. After I get about 4" deep I'll turn the wood around and start boring from the other end.

I'm holding the wood on the lathe with a 4 jawed chuck.

Jim