Mortise through 3" hard wood?

[Gary R Katz]

I'm trying to cut 3" deep mortises through Oregon White Oak, an exceptionally hard wood. This wood's Janka rating (I don't know what a Janka rating is) is 1660, compared to red oak at 1320. The lumber came from a large tree in our yard and I'm rather attached to it. I'm (trying to) build a variation on Mr. Barnsley's Hayrake table and the 3" thick legs have 2" X 7/8" through mortises for the lower stretchers. I've drilled out most of the waste and I'm having trouble getting the mortises parallel and square. I've tried using a mortiser but it can only shave small amounts of this hard wood. I also tried an up cut bit on my router table but that wasn't yielding accurate cuts. The primary challenge is the 3" thickness of the piece. I have to cut part way through one face, then flip the piece and finish on the other face. I can finish it off with chisels but it's a long, slow process and I don't seem to keep the sides parallel. I'm sure there are at least a dozen good ways to do this, so whatever help you can offer to turn some of this tree into our dining room table would be greatly appreciated.

[Bob Lang]

You're stuck working from both sides, but assuming there are shoulders on the tenon you only need to be perfect on the exit hole. You can taper the mortise slightly in the direction of the tenon to make trial fits easier. A good rasp or float will be extremely helpful; work from the outer face to avoid blowing anything out on the pretty side. At that length and thickness you will have tremendous strength in the finished joint even if it gets sloppy. Make a practice joint in scrap to see what you can get away with.

Bob Lang

[glenn bradley]

If the bulk of the hole is there I would probably go with a wide chisel keeping my Worksharp on the bench and touching up as I go. For a powered solution, a template with a reference "fence" or two to position the hole and route from each side. Whiteside makes extra long spiral bits for the Mortise Pal. I have the Mortise Pal but, find other uses for the extra long bits as well; your case in point ;-). You could use the 1/2" and add a bearing or use a template collar.

[Prashun Patel]

As a last resort, you can always rip the legs in half, cut the mortises as dado's and glue back the legs. If you glue it well, it can end up darn near invisible.

[Greg Hines, MD]

I would make a template, and then use a plunge router with a collar to guide the bit, and a long straight or spiral bit to hog out most of it. Then chisel the corners square, if it matters or leave them with a radius.

[Loren Woirhaye]

This is a way to do it:
http://woodworker.com/radial-saw-mor...su-889-372.asp

[Prashun Patel]

Gary,
Also, if you're having trouble lining up your router on both sides properly, then I've seen this done several times with a saddle-style jig that has templates on both sides of the piece that are locked in place by an adjoining saddle and keeps them perfectly lined up, so you don't have to move the jig when you flip.

I also second the idea of establishing square shoulders with a plunge router then chiselling the rest.

You can also get 1/4" more depth from your plunge router by removing the jig after initial routing, and switching to a pattern routing bit (top guided bearing). The bit will ride in the established mortise shoulder and clear some more depth for you.

[Gary R Katz]

Bob, thanks for reminding me it's only going to show on the pretty side. I've been able to get close to clean parallel sides with a lot of chisel work but tapering the mortise would be a good way to focus on the finish side having the tight joint.

[Gary R Katz]

I might just invest into a long bit since i have other mortises besides these 4 leg pieces. A long bit would get me started with straight parallel sides.

[Gary R Katz]

Wow, never thought of that idea! I'll keep it as a last resort, definitely.

[Jeff Duncan]

Might be a long shot, but a couple postings on several WW sites indicating your looking for someone with a large mortiser you could borrow time on could be an option? There's a lot of old beasts out there that I'm thinking would likely handle 3" depth of cut....it's just finding one locally that'd be the trick

good luck,
JeffD

[Mel Fulks]

As good as the mortisers are ,the chisels are expensive and it's easy to ruin them on real hard wood so you could end up with a surprisingly high bill. If you decide to sub them look for someone with a chain mortiser. I think for just that one piece of furniture I would use drill press to make straight round holes ...then chisel the rest. I know that doesn't sound traditional but in a way it is. Amateurs and even tradesmen working slightly out of their regular sphere have done that on old work.

[Mark Wooden]

See if you can find someone with a lock mortiser

[Guy Belleman]

Lots of good ideas. I would probably be too impatient, just drilling out the waste and hand chiseling out the mortise, many days before any new tool or attachment arrived. Did 10 in a day through 4" and 5" oak several years ago. Looked great, of course, my sharpening skills gotten increasing better, and my hands were sore/tired, but satisfying work.

[jack forsberg]

if you were closer i do it for you in minutes. My Stenner cuts though mortises 6" deep from one side with a single finger.