What is the difference from a mortise router bit and a spiral up cut for box joints?

Can they both be used to make a box joint?

Spiral up bits are usually used on router table operations.

Here's an article comparing the various straight cutting bits-

http://www.woodcraft.com/Articles/Articles.aspx?ArticleId=445

Spiral bits cut a little cleaner and are better for plunge operations. I've cut box joints with both. 

 

 

And really depending on where you are going to use this. If you are going to use it in a table router you would probably want a down spiral for the box joints. That way it is pulling the shavings down into the table for the dust collector to take away. If you are using it in a hand held router, then the up spiral will lift the shavings and if you have dust collection it makes it easier to get rid of the shavings and dust.

A straight bit will also work for the box joints. The dove tail jig I have will also do box joints and you just use the straight bit.

 

 

Old topic, still a great question.

Moved up from the archives

It's been a while, now. Which one did you choose, @Ron Altier? And, how did it work for you?

I have the Incra BJ jig and I set it up on my router table and got a lot of tearout on the outside of the board. I now use it on the table saw with no tearout.