Process Error - Advice, Please

[Mark Maleski]

I'm building cabriole legs for a Chippendale footstool, and I realize I've made an error which could ruin the legs if I'm not careful. At this point in the build, I'm ready to chisel the mortises in the top of the legs for the connecting rails...but I've already cut off the material for the kneeblocks. I realize now that was a mistake, because I'm left with only 1/4" of material between the end (or top) of the mortise and the top of the leg. I thought about trying to clamp the material for the kneeblocks back on before chiseling, but am worried that any small gap between the two pieces will still allow blowout. I think instead I'll drill out the top of the mortise and chisel as planned below that hole. Any other suggestions on how I should proceed?

[Bill Houghton]

I may not be visualizing your problem correctly, in which case, please forgive me. If I understand you correctly, your problem is that you've got just 1/4" of short grain between the top of the mortise and the top of the leg. If that's so, you may have a design problem, not a process problem - that seems like very little material to resist the desire of the tenon to break out the top of the leg. Perhaps making your tenons narrower and your mortises less tall, with the reduction all occurring at the top of the leg, would be better.

As to how to do the mortise, you might consider drilling out the entire mortise, and then carefully paring the sides and squaring the corners.

If that fails, an open mortise at the top, pinned for mechanical connection, may be your fallback.

[Mark Maleski]

Bill,

Yes, you have it correctly but I left one detail out - there will be a ~45 degree haunch at the top of the mortise, so for most of the depth of the mortise there will be close to 1/2" of material between the mortise and the end (top) of the leg. I'm comfortable with that once the piece is complete (I'm following a tried & true plan) but not when I'm whacking the mortise chisel into the leg.

Thanks for your suggestion about drilling out the whole mortise; I'm equivocating on that approach. Since I've only trued and squared two sides (this is a neander project) I'd have to drill with a brace (i.e., not use the drill press), and I believe I'll be better able to keep the mortise walls square with a chisel than with a brace...thus my thoughts about drilling just one hole and then going to the chisel.

[Don C Peterson]

Been there, done that...

What worked for me was to adopt a new style of hand mortising. I used to start on one side and nibble away to the other, rinse and repeat until the mortise was deep enough. Now, I start in the middle and create a V which is as deep as I need, then work out from the center. What this allows me to do, if necessary, is to pare down without using a mallet, thus generating little to no force that would blow out the top. Worked great for me YMMD.