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View Full Version : Mortise Chisel Cross Grain OK?



Brian Kent
04-30-2009, 2:25 PM
I am using wedged tenons to secure a shelf to a side - 3/4" QS white oak. The tenons will be 3/8" x 2". I need to cut the mortises cross grain since the shelf goes cross grain to the side.

I usually chop mortises with a Ray Iles 3/8" mortise chisel. Can I use this cross grain without chipping out the oak?

I can picture doing this with a starter cut with bench chisels on the long side of the mortise.

I would prefer not to drill holes first because my drilled mortises never look as well as the chopped ones.

Thanks

Brian

Sean Hughto
04-30-2009, 2:40 PM
This is going to be a through mortise? These aren't fox wedges, right? And these only have to traverse 3/4 inch of material? If I've got his right, I would not recommend chopping them with a mortise chisel. Careful marking on both sides, followed by drilling and paring are a better bet for a good fitting and attractive through mortise and tenon in this sort of situation.

Brian Kent
04-30-2009, 2:59 PM
Through mortise with a wedge - yes.

Fox wedge - I'll let you know after a google search.

Found Foxtail wedge in Gary Rogowski's Joinery book. No, it is not that. I am making a wedged through tenon. The wedge can split the tenon the long way.

If you recommend drilling, I need to improve my technique. What size bit would I use - just under 3/8"?

Brian

David Keller NC
04-30-2009, 3:19 PM
Brian - Mortise chisels are designed with the edge to be used perpendicular to the grain, and with oak being as readily split as it is, I wouldn't recommend stepping down the length of a cross-grain mortise the way one would with stile in a cabinet door.

But... you could certainly use a smaller mortise chisel cross-ways in the mortise so long as the width of the mortise is sufficient.

Sean Hughto
04-30-2009, 3:38 PM
What tools are available to you? Do you have a drill press? A hand drill? A brace?

I assume you don't have a hollow chisel mortising machine?

Do you have either a router plane or electric router?

Assuming you have a drill press, or can at least make a jig to guide your hand drill straight and plumb, you out to drill out as much as you can from inside the knife marked rectangles (enter from the side that will be visible on the finished joint). Then carefully use your chisels, working from both sides, to get rid of what's left. Always keep in mind the show side as this is such a strong joint that slop break-out etc. on the inside will be nonconsequential, but the show side needs to be pretty.

As I understand your joint, you will have one wedge centered on and parallel to the long dimension of the tenon? This will help onthe long sides when it compresses the long edges as the wedge is driven. In other words, the most critical edges onthe show side ar the short 3/8th inch tall ends of the mortise.

Brian Kent
04-30-2009, 5:05 PM
Drill press is too small to reach where the mortises are.

I have braces and electric hand drills. I can use a 5/16" bit to clear it out.

his is for a saw till. I'll do this first on the side of the saw till that will be facing the corner, so I can screw it up 6 times for practice.:D

Pam Niedermayer
04-30-2009, 5:05 PM
I've cut mortises in very small material with no problems, say 1/4" square for kumiko in shoji. Make sure your chisel is very, very sharp. 3/8" would be a real test, though, the mortise would be 1/8"? And the wedge?

You could cut what is essentially a slot, with the top larger than the bottom, then angle your wedge to match. That would cause less stress on the mortise.

Pam

Sean Hughto
04-30-2009, 5:09 PM
Is this a shelf or a cross brace at the back. I'm getting confused as to the grain orientation of both boards that are meeting. It matters to the extent the wedges should be perpendicular to the grain in the mortise board.

Brian Kent
04-30-2009, 6:02 PM
Here are 2 photos and 2 quick and sloppy sketches. These are attaching the shelves to the sides. There are actually 5 wedged through tenons on each side.

Each board is 3/4" thick. The tenons are 3/8" thick.

I am attempting to improve upon (or at least modify) a design you can see in this thread:
http://sawmillcreek.org/showthread.php?p=1119190&page=2

Chris Friesen
04-30-2009, 6:07 PM
I am using wedged tenons to secure a shelf to a side - 3/4" QS white oak. The tenons will be 3/8" x 2". I need to cut the mortises cross grain since the shelf goes cross grain to the side.


The suggestion in Woodworking magazine (you'd think I was a shill or something) was to use a router with a template and a small pattern bit for this purpose, then leave the template clamped on and use it as a guide to chisel the corners square.

Brian Kent
04-30-2009, 6:16 PM
The suggestion in Woodworking magazine (you'd think I was a shill or something) was to use a router with a template and a small pattern bit for this purpose, then leave the template clamped on and use it as a guide to chisel the corners square.

Now there's a clever combination of electrons and eye-hand coordination.

I'll keep the idea as a possible.:)

Sean Hughto
04-30-2009, 7:50 PM
It's all doable. I'm not sure it's an improvement. Dovetails at the bottom would be just as strong or stronger. A sliding dovetail for the middle shelf would also be just as strong or stronger.

As a general matter, I find I have more success tweaking a tenon to fit a mortise than vise versa.

Brian Kent
04-30-2009, 8:33 PM
I tried the drill and bench chisel combo and it worked fine this time. At least close enough for shop furniture:rolleyes:.

As far as the improvement, I forgot that the discussion was on the other thread. When we started looking at the plans we could see that at the top the dovetails were on the long grain. That started some thoughts about adjusting all of the joinery, especially since in my shop white oak and dovetails are not currently on speaking terms. I had one too many tails break off when I was trying to use some particularly interesting (fragile, crispy, breakable) grain for dovetails.

So on the top it will be an improvement, on the sides and botom just different, and I did the mortises first so I can draw through them before I cut the tenons to shape and chisel them to size.

Thank you for all of your help!

Brian