Angled Mortise

[jspelbring]

I'm trying to build the octagonal taburet table is the Arts & Crafts Furniture You Can Build book. My problem is that I need to cut some 3" x 3/4" through mortises in the legs for the cross pieces (pegged tennon). The plans call for the mortises to be angled at 8 degrees. I tried using my drill press (after fighting to get the table to tilt) with a 3/4" bit, but it came out looking pretty rough. I've tried to clean it up with a chisel, but I can't seem to keep the angle right.

Does anyone have any suggestions on an alternate way of cutting these buggers?

Thanks in advance.

[JimD]

I would cut a wedge on the BT3100 to support the leg during cutting the mortise. A plunge router makes a good mortise but I like my dedicated mortiser even better. A drill press will probably work well but I have not done it that way.

[drumpriest]

I use a plunge router for my mortises, but hitting a 3" depth would be difficult. The dedicated mortiser is probably the way to go with this problem.

[gary]

Can you give a little more detail on the legs (wood type, dimensions,etc) and where the mortises will be located? I'm wondering if it's possible to rip the legs in half, cut 1/2 mortises with a dado blade and then glue them back up. Done right, the joint should be almost invisible.

[SARGE..g-47]

Evening js..

"I tried using my drill press (after fighting to get the table to tilt) with a 3/4" bit, but it came out looking pretty rough. I've tried to clean it up with a chisel, but I can't seem to keep the angle right".... js

What precisely is looking pretty rough? Exit hole, entry hole, did the angle come out in-correct, did the drill bit wander on initial entry outside the marked rectangle of the mortise and did you have it blocked on the exit to prevent tear-out? Was the chisel sharp? Was the stock properly clamped to prevent movement under the press and chisel?

Just a few questions that might lead to a reason it could have looked rough!

Regards...

[Thom2]

is it possible to start with an oversized piece of stock and cut the mortises square, then cut the blank to 8 degrees???

I have no idea what the final project is, just throwing out an idea

[JR]

Mortises were always "rough" for me until I got a dedicated moriser. I can't imagine trying an angled mortise with a drill press.

Having said that, a forstner bit might help. It should allow you to cut at an angle without deflecting as a twistdrill would do.

Also, it may be stating the obvious, but you need have a fence on your drill press to move the piece along uniformly. You'll never get an even set of holes without one.

JR

[jspelbring]

Follow up

I love this site! Quite a few answers came through. As to the details:
I'm using white oak - 3/4" stock. The mortises are 3/4" wide by 3" long by 3/4" deep (through).

My mistakes:
1. I used a spade bit (it's the only bit I have that's 3/4"
2. Didn't set up a fence on the DP

As to my definition of "rough", I had some tear out, and found it very difficult to maintain the 8 degree angle when cleaning up the mortise with a chisel.

Gary, I like your idea of rip-dado-glue.

Somewhat shamefaced, I have to admit that I do in fact have a mortiser. No idea on how to tilt the table, (plus my largest bit is 1/2"). I didn't think of simply making a wedge to put under the stock (dooooh!).

So, time to get more familiar with the mortiser (got it a few months ago, but so far, I've only used it on a small M&T picture frame.

Given that I really like the look of the Arts and Crafts stuff (and quite a few of those have angled sides), I may need to make some re-usable wedges -- unless I figure out how to tilt the mortiser table (the smaller Delta).

Anyway, I'm rambling, haven't had my coffee.

Thanks everyone!

[SARGE..g-47]

I have a dedicated mortiser too, JS. But.. on that tricky 8* angle and the fact that it is a through mortise that will show, I would take a few extra steps that would'nt be necessary on a standard 90* mortise.

I would cut a small hard-wood block at 8* to use as a guide. Lay out the mortise and then clamp the guide to one end of the lay-out. At that point I would use a mortise chisel to manually start that narrow 3/4" end and penetrate to about 1/2". Reverse the block and do the same on the other end. Now, I would clamp a flat piece as a guide to the outside of the long portion of the lay-out and use a hand pressure with a sharp chisel to outline the sides. 1/8" deep is enough. Pare out just enough to give you a visual foundation to work with on the mortise machine.

Now to the mortiser to finish what you started. Don't forget to use a backer block of hard-wood to eliminate tear-out on the opposite side. Remember that side is the most important as it will be the show-piece side. The shoulders of the tenon will cover the entry side of the mortise so it doesn't have to be perfect. It is more critical on the entry side to be sure the tenon and especially the tenons shoulder is square (in your case 8*). I usually make tenons a tad over-size and take them down with a paring chisel, wood file, shoulder chisel or block plane till a good fit is reached.

If you are new to mortising, you chose a bit of a tricky way to enter. But.. you can and you will succeed with a little thought and patience. Keep chisels sharp and make sure you have the mortiser bit set up square to the fence. Clamp everything as it will move under under pressure.

And you mentioned you don't have a 3/4" mortiser bit.. Do you have a 1/4" or 3/8" bit. If so you have a 3/4" mortiser bit. 1/4" x 3 = 3/4" .. 3/8" x 2 = 3/4"..
Successive passes will get your results without purchasing the 3/4" bit. It will take a little longer... SO WHAT!

Take your time and think things through before you cut. You might just be surprised and get it right the 1st time without a costly mistake. You don't have dead-lines as a commercial WW does. Use that advantage to the fullest.

From one newbie to another.. Good Luck!

[JimD]

I cut through mortises from both sides. For an angled mortise you'd have to flip the wedge around. It eliminates the tearout problem and also puts any misalignment in the center of the leg rather on the outside where it would show.

I cut a 3/4 mortise by making two cuts with either a 3/8 or 1/2 inch chisel. It has worked fine for me so far. I think the largest I've made this was was a 7/8 wide through mortise.

Jim