Router bit for cutting Deep mortise

Just make sure that you have positive control of the router cutting holes that deep--if you don't, it's easy for the bit to grab, rattle around a bit, and break.

By positive control I mean a jig that doesn't let the router move any direction but the direction you want it to, with no play to speak of. Don't rely on hand pressure against a fence.

Found that out the hard way.

While spiral bits are wonderful in many ways, I wouldn't use one for deep mortises until I was sure I could do them reliably with a straight bit--the reason is that they cost a lot more than straight bits and being solid carbide they're easier to break.

Learned that part the hard way too.

The jig doesn't have to be anything elaborate--you can cobble one up out of a scrap of plywood and a couple of pieces of 2x4 that will do the job, but it has to keep the router under control. If you need a mortise wider than the bit, offset the router in the jig a little bit, then reverse the jig to get your second cut (and do that for each step of depth, don't cut all the way through then try to widen it--you may get away with it but it's asking for trouble).

And as Allan Quatermain said to Tom Sawyer, "take your time, you've got all the time in the world".

Depends...oak or pine (hard or soft)?

Your life would be easier if you drilled a 1/2" starting hole, then a series of 3/8" holes through the 4x4 before routing.

For plunge routing, and particularly with my Multi-Router, I use "end mills", instead of router bits.

I generally buy them from:

Call Travers, tell them what task you are doing with the end mills and what your needs are, and they will tell you precisely what you need without you having to wade through the countless choices on their web site/catalog.

Trust them ... good company with excellent, well informed sales staff.

For a guy who has not cut a mortice yet, you are well informed. More on this, routing & mortices:

Bill

Thank you for sharing both of your lessons that you "learned the hardway"--I was ignorant of both issues and was likely to repeat them--especially the one about "relying on hand pressure against a fence". Secondly, in view of all the accolades given to carbide, I did not consider it's brittleness--clearly a factor here! If there's a lesson here, it's got to be "don't take too much for granted!"

Bill

Done it with a PC 693 and a long 1/2" carbide bit. 1.5 hp is more than adequate, since you can only take shallow passes without clogging the mortise with chips. Hogging out with a drill before routing is definitely advisable.

I believe the 4by4s will be SYP. Your idea involving drilling makes a lot of sense! Before this task is complete I may have a DP--not sure! : ) Thank you!

Hmm... Harbor Freght has one with a 2" spindle stroke for $59.99 (comments?).

Bill

Other than an academic exercise, why bother?

A 4" long, 1/2" wide tenon cut to fit the above mortise?

Lew

Sometimes it pays to look around a bit...

Lew,

Garrett Hack used two (double) 3" wide by 3.5" long tenons at the joint of each trestle post and trestle shoe in his design (which I am more or less following). To borrow one of your expressions, perhaps be has "guilded the lily". What would you do instead?

Bill

---------------------------------------------- A 3" wide x 3-1/2" long tenon is a totally different world than a 1/2" wide x 4" long tenon.

A tenon that is more about 2-1/2 or 3 times longer than it's width just is poor design IMHO.

Lew

(...i think he's ripe for a 'bot...)

Not till after he's spent for the _entire_ Festool lineup...

..._then_ he'll be ripe. :)

Is it a plunge blind hole ? or is it a cut from side or end ? How will the wood escape ? Up spiral might be important if blind.

Mart> I wish to cut 1/2" wide mortises all the way through a fourbyfour (cutting

Plunge hole is blind. I'm hoping that if I don't cut too much at a time, that the wood "will find" a way to escape! :) Others suggested drilling a few holes..that would clearly be helpful in giving the wood a place to go as well. I'll be buying an extra 4by4 to practice on..

Bill

Yes, so what do you properly call the dimension which is the short side of the rectangle which is the top of the mortise? Is the short side of this rectangle called the mortise's "width"? Clearly, from your first reply, the answer is no.

From what I can tell, it appears that common nomenclature may just be to measure the length, width and thickness of a tenon and just refer to the tenon's mortise and leave it at that. I'm sure those in industry have better terminology.

Bill

You can get spiral bits made of steel. They are sharper than carbide.

ERRATA:

The phrase "I wish to cut 1/2" wide mortises" should be replaced by "I wish to cut mortises having 1/2" **end thickness**".

This is in according to Terrie Noll's book, "The Joint Book".

My thanks to *Lew* for trying to maintain a decent standard for the clarity of communication around here!--and for yet another valuable lesson. "Good enough is seldom good enough..."

Bill