Is it just me or is .........

[lcm1947]

a mortising bit the exact same bit as a straight bit? I just happened to look at these two bits earlier today and I could not tell one bit of difference. Anybody know if they are the same bit just called something different?

[RodKirby]

Have a closer look at the end of the bit - a "normal" straight bit is not designed to plunge-cut.

[LarryG]

As Rod says, a mortising bit has end cutters. However a straight bit can be used for most plunge-type cuts if the router can be moved laterally a bit as the plunge is made.

[Tom Miller]

There might be some confusion in terms here. Some sellers offer a mortising bit for door hinges (still just called a mortising bit), which do not seem to have end cutters.

Regards,
Tom

[lcm1947]

Thanks guys. I think you're right Tom. This did say for door hinges. I'll check out what a regular mortizing bit looks like. I wasn't aware there were different kinds. Thanks.

[crokett]

I use an upcut spiral bit for both mortising and in place of a straight cut bit. It plunge cuts which a straight cut doesn't do and it clears chips better than a mortising bit.

[lcm1947]

Thanks Crockett I didn't know that about the spiral bit. Actually I was wondering where they would come into play in the first place so now I see and good point about using them in place of a straight bit. I'll have to try one for mortising too. Most bits you can kind of figure out what their for but the spirals had me going there until your help. So what would a downcut spiral be used for?

[LCHIEN]

...
So what would a downcut spiral be used for?

The upcut spiral has the spiral in a direction so that material is pulled to ward the router (up is understood to be relative to the router in handheld use so when in a table mount the material is actually pulled down).

This results in some hairs on the edge of the cut on the top of the wood (nearest the router).

A downcut spiral will push the fibers down into the cut and shear them off on the side nearest the router making a clean top cut. The disadvantage here is that in a dadoing situation the sawdust is packed into the groove. On a through cut the hairy cut will end up on the bottom side (again relative to the router to top).

An up-down spiral bit is available with two counter spirals. This will make clean edged cuts on top and bottom but the bits are even more expensive than relatively costly single spiral bits.

[lcm1947]

Ok got it, thanks Loring. Yes, I just noticed that they are quite a bit more expensive then buying the bits I'm used to but still might try one out. Sounds like a handy type to have.

[drumpriest]

I'm with those guys, I use a spiral bit for all mortising. It cuts so much more easily it's sick. If I'm mortising for M&T with the router, I plunge the full depth on the ends, then clean out the mortise in between in 1/8" increments.

[LCHIEN]

Ok got it, thanks Loring. Yes, I just noticed that they are quite a bit more expensive then buying the bits I'm used to but still might try one out. Sounds like a handy type to have.

If you get a 1/4 spiral upcut, which is probably the most popular spiral bit, they run about $15. Buy two because they are quite brittle and the spiral flute in them makes the cross section actually much thinner than you imagine. Most people break one by the time they get the hang of it.
Don't try and take too big a bite, 1/4" deep per pass is the maximum! More like 1/8th is recommended.

[lcm1947]

Thanks again guys and Loring I guess I must have looked at Woodcrafter bits or something because the spiral bits at MLCS are $15.00 like you said. I will sure get a couple to play with now for sure. Glad you pointed that out. MLCS also mentioned where and how to use them so that was handy too. Thanks again.