1/4" endmills

[Brent Leonard]

can you rout mortises, using a router and shopmade jig, with a end mill....

deeper than the flutes or cutting edges on the bit?

http://img528.imageshack.us/img528/8174/endmillbq8.jpg (http://imageshack.us)

Basically, I want to cut some 2 inch deep mortises. This long reach end mill has a cutting edge only 3/8". Any issues? Can I go deeper than the flutes or cutting edge?

I also understand the latteral forces involved, the deeper you go can break a bit, so going SLOW..... goes without saying.

[Frank Drew]

Brent,

I've cut lots of mortises with two-flute upcut end mills, but none with mills with such short fluting. My normal procedure, with both router and horizontal mortiser, was to plunge cut the ends of the mortise to full depth then waste the rest sweeping side to side, usually in increments of around 1/4" but that would depend on the hardness of the wood and how the cutting was going (your bit will tell you if you're being too aggressive.) That method would probably work fine with your mills since I was often cutting deeper than the fluting on my bits, but I can't say for sure.

I've used both HSS and carbide and found that the inexpensive HSS worked fine. If the mills you have don't work it should be easy enough to get some more appropriate ones.

[Jeff Duncan]

I don't know, but I wouldn't want to try it. A 1/4" bit in a router setup is going to have an awful lot of lateral play at that length. Controlling it will be tricky, having any accuracy at the bottom of that mortise seems highly unlikely. For comparison, I use a slot mortiser (big heavy old sucker) with a 3/8" end mill about 2-1/2" long to cut 1-1/2" deep mortises for interior doors and there's a bit of runout to deal with.
On end mills the ctting edges are sometimes a little wider than the shank, there's a term for it but it escapes me at the moment. If yours is this style then you should be able to cut deeper than the actual cutting edges. However you'll probably have to do some chip clearing fairly often.
What type of project is it that requires the 1/4" bx 2" deep mortise anyway? Give us a little info and maybe we can suggest some alternatives.
JeffD

[Tom Cross]

No, I would not try it. I have tried routing mortises that were 1/2" deeper than the end mill cutting edges and got lots of wood burning, not pleasant at all.

[Bruce Page]

You’ll likely get a little burning as you get deeper unless you can keep the chips blown out, but it’ll work. If you have a VS router, I’d run it on its slowest setting and take very light cuts with a slow feed rate. Believe it or not, end mills designed to cut metal don’t do as well in wood because of the different sharpening geometry (I’ve burnt up a lot of end mills).

[Frank Drew]

Upcut bits help with chip clearance but I still used an air gun to blow out the mortise every other pass or so; two-flute bits cut easier in wood than four-flute, IMO.

If you're making, say, a cabinet door frame out of 3/4" material, your mortise and tenon will have to be 1/4" or maybe 5/16". I've done lots of mortises in those dimensions without any great difficulty; as I said above, your bits will tell you if you're trying to take too much per bite.

[pat warner]

You need 6-10/1000" more cutter diameter than shank to cut a mortice deeper than the flute length.
You be burning the walls of the mortice and destroying the cutter other wise.
Routers (http://www.patwarner.com)