The first key is fitted, only three more to go. Someday I will figure an easy way to chop/make the key mortise but for now they are a PITA because they are short, narrow, with both ends angled, and deep. It doesn't get much worse. The only good news: The only critical surface is the front end where the key mates and I guess the fact there are only four of 'em.
BTW, the loose fit is on purpose, it is needed to allow the base to fit together and come apart. In fact as I look at this one I'm thinking it may be a little tight.
That is likely it for today, shop is hot and it is the first day off in a few so street running and other duties call.
ken
Looking at the workbench plans made by Will Meyers, the tapering of the wedge is not given but it is in the text (originally on WK fine tools) republished on his site.
ReplyDeleteA calculation gives about 4.2°. It seems up to 7° might work.
Sylvain
Sylvain,
DeleteYour calculations sound about right. I've roughly measured the angle of my key and it comes out ~7*. Two things are important, that the key's angle to not be too steep or shallow and the mortise wall matches and is reasonably smooth but not too.
ken
I hadn't considered that BOTH walls of the wedge mortise were angled, but I see that now. With it being a through mortise on fairly wide stock, it's no wonder it's a challenging mortise to cut.
ReplyDeleteMatt,
DeleteThe mortise being short even at the wide top and deep you soon run out of room to lever the waste. Once you get 40mm or so deep things slow to a crawl. From the bottom (narrow side) it happens sooner. The mortises are so narrow and deep I expect drill and pare would be a disaster although on the last mortise once I had chiseled out as far as was eazy from both sides I did drill to break through and it worked well.
The good news, just two more to go and odds are I can hide from MsBubba's line of sight long enough to finish them today. Then it is on to the slab and vise install.
ken
As the side of the key which bears on the leg must in no way bear on the corresponding mortise end, that side of the mortise is not critical and could even be vertical with no effect on the wedge functionality.
ReplyDeleteIt must work even if the leg and the wedge shrink.
Sylvain
Sylvain,
ReplyDeleteI have thought about both making the back wall vertical and the mortise longer. The biggest problem with either is weakening the tenon which is kinda small for the job it has to do. The width of the tenon is limited by the width of the leg and the leg mortise. It's all a balancing of size and strength and you just hope your set of compromises work. So far they have.
ken
Of course one does not want a snapped tenon, that is why I pointed out "on the wedge functionality".
ReplyDeleteAs for the extra length theoretically, anything more than zero should be enough if you don't expect any shrinkage or compression. In practice, to be on the safe side, Will Meyers added 3/16" which would not weaken the tenon.
Sylvain