Does anyone do this?

[abentley]

Does anyone use a 3/8 downsprial bit to cut dado and tenons? I cut my dados 3/8 deep. Right now a use a 1/4 downsprial. I would like to do the cut in one pass. How would you set this up, 55% dado tenon thickness and .38 depth?

[Gary Campbell]

Alan...
I use both a 1/4 and 3/8 downspiral depending on the dado/mtl width. To set this up you would need to:
Assign a unique tool number to the 3/8
Set it up in the tool operations BEFORE the 1/4"
Set speeds and feeds appropriate for your machine

On the design end:
Dado depth must be .375 (or greater)
Tenon thickness must be .375 or greater. (Mtl thickness * % must be greater than .375)
Fit or depth clearance numbers do not factor into tool selection

When you say "one pass" can I assume you mean one depth pass? The 3/8 bit should allow this. If you mean a single cutting pass vs. traversing one end of the dado to the other and then returning, it wont change. Dado geometries are always rectangles. The bit, no matter what size, will always cut an inside profile of a rectangle. (4 sides) In some cases where the bit and rectangle are the same width, there may be little or no movement on the end cuts, but a rectangle is cut, nonetheless.

[curtiss]

Gary,

In general, when is it best to use a spiral downcut over a 2-fluted bit ?

Is a 3/8ths bit with 2-flutes more likely to chip out as it exits the material ?

Do you use Cabinet Vision ?

thanks, cdj

[ken_rychlik]

I use straigh 2 flute for dados, and it works fine. I do think down spirals last a little longer, but then they cost more too.

[Gary Campbell]

Curtis...
I use a downspiral for cutting dados and a lot of cuts in solid wood. They are a good choice anytime top surface quality is important and the cut is not extraordinarily deep, as they deflect more than some others. (or take shallow passes)

Before I had the ATC machine I used a mortise compression for this purpose and cutting my outlines. Higher cost, but 1 bit does most everything.

I havent had any issues with any bits chipping on a retract.

No on the cabinetvision. I use eCabs. David Buchsbaum is the CV guy on the forum.