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Tenon Design Question - cputnam - 02-20-2020
For table or bench legs, why do we cut 4 shoulders? Are the two shorter ones all that useful? I am thinking specifically about legs that are wider in one dimension. I the tenon is /13 leg thickness, then would not cutting some tenon length (to create the two smaller shoulders) reduce tenon strength without adding much in the way of top support? Cutting the little shoulders would seem to gain little - just the 1/3 tenon width for however much one cuts off the tenon. I'm really thinking more about bench legs than tiny tapered legs on a tea stand.
RE: Tenon Design Question - mike4244 - 02-20-2020
(02-20-2020, 01:20 AM)cputnam Wrote: For table or bench legs, why do we cut 4 shoulders? Are the two shorter ones all that useful? I am thinking specifically about legs that are wider in one dimension. I the tenon is /13 leg thickness, then would not cutting some tenon length (to create the two smaller shoulders) reduce tenon strength without adding much in the way of top support? Cutting the little shoulders would seem to gain little - just the 1/3 tenon width for however much one cuts off the tenon. I'm really thinking more about bench legs than tiny tapered legs on a tea stand.
By making 4 shoulders the mortise dimension does not have to be dead perfect. The shoulders hide small imperfections .
mike
RE: Tenon Design Question - fredhargis - 02-20-2020
I had always thought like Mike, the shoulders hide some sins, but on bench legs....who cares??? For working pieces I'm very much function over form.
RE: Tenon Design Question - jteneyck - 02-20-2020
Same as mentioned above. But I'll add that the 1/3 "rule" only applies to hand chopping mortises. You can gain strength in 3/4" stock, for example, by cutting a 3/8" wide mortise with a router or chisel mortiser instead of the traditional 1/4" width chopped by hand. 1" stock gets a 1/2" mortise instead of 3/8", etc.
John
RE: Tenon Design Question - cputnam - 02-20-2020
Thank you, gentlemen! As you may have suspected, the legs in question are a 3 part glue-lam for which the centerpiece becomes the tenon. Just could not figure out why I would want to weaken the tenon since aesthetics are not part of the equation. Had enough trouble perfecting the two shoulders I've got now.