I'm familiar with the usual guidance regarding interference fits with M+T joints where you want to have it slide together with a hand-firm fit such that it's not overly tight but that the tenon won't slide out on its own if the joint was inverted.
My curiosity is does this interference fit need to be true for the whole length of the tenon, or is there some tolerance if, say the first 1/3 was a little shy of the mortise walls - I dunno, let's say by a 1/64-1/32 on each cheek - but that the remaining 2/3 are a good fit. Would this still qualify as a good joint?
My thought experiment here is with a longer, wider, thicker kind tenon. Dunno if it'd matter on a smaller, more delicate scale but just for the sake of argument let's say it does and just narrow discussion down to the beefier stuff - tenons a few inches of inches long and 1/2" or more thick.
If the tenon were intentionally or unintentionally misdimensioned toward the last 1/3 at the end, how much would it matter to the overall strength of the joint if the tenon's remaining 2/3's had that interference fit and good, tight shoulders?
If it does matter, what route would one take to re-dimension the errant part of the tenon? Mill a thin wedge of material and glue it in place with the correct grain orientation on each side of the tenon?
Reason for asking is I have some tenons of this nature coming up and I'm not 100% if I'll be able to/how to maintain ridgidly parallel cheeks on opposite sides of the tenon if hand-tweaking becomes necessary.
Any thoughts & ruminations appreciated.
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I'm no expert but I'm inclined to believe that 2/3rds of a correct M&T is sufficient as long as we're not talking a front entry door. The last time I screwed up some tenons I went ahead and took them from 1/2" thick to 1/4" thick then glued on new cheeks and recut them....
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For six bucks I could have been insignificant on a popular forum. ---
I'm familiar with the usual guidance regarding interference fits with M+T joints where you want to have it slide together with a hand-firm fit such that it's not overly tight but that the tenon won't slide out on its own if the joint was inverted.
My curiosity is does this interference fit need to be true for the whole length of the tenon, No or is there some tolerance if, say the first 1/3 was a little shy of the mortise walls - I dunno, let's say by a 1/64-1/32 on each cheek - but that the remaining 2/3 are a good fit. Would this still qualify as a good joint?I shoot for a few thousandths difference in the fit top to bottom if it get solid about halfway in but still presses in quit.
My thought experiment here is with a longer, wider, thicker kind tenon. Dunno if it'd matter on a smaller, more delicate scale but just for the sake of argument let's say it does and just narrow discussion down to the beefier stuff - tenons a few inches of inches long and 1/2" or more thick.
If the tenon were intentionally or unintentionally misdimensioned toward the last 1/3 at the end, how much would it matter to the overall strength of the joint if the tenon's remaining 2/3's had that interference fit and good, tight shoulders? I would be comfortable with your suggestion but be aware that you can make the mortises to wide and weaken the joint. the 1/3 thickness of the stock is a good rule of thumb.
If it does matter, what route would one take to re-dimension the errant part of the tenon? Mill a thin wedge of material and glue it in place with the correct grain orientation on each side of the tenon?As Fred said plane the tenon down so you can add a thick piece of veneer to each side then re fit the tenon. If you don't want to mess with veneers just glue a thick piece on each side then re do the joint.
Reason for asking is I have some tenons of this nature coming up and I'm not 100% if I'll be able to/how to maintain ridgidly parallel cheeks on opposite sides of the tenon if hand-tweaking becomes necessary. A shoulder plane like a #92 Stanley is a good investment once one begins working tenons
Prolly the best plane I've ever used for tenons is a left-handed #140.. I'm right-handed, the left-handed gets pushed away from you against a stop on the bench while you hold the piece with your left-hand.. the open side cuts right into the shoulder, and the skew angle of the blade just peels off the cross grain of the cheeks.. Perfect piston fit tenons almost every time..
You've received all good advice. I will add one more thought. When disassembling your M & T after a dry fit, do not be tempted to wiggle the tenon loose as it can ruin your perfect fit. Instead use a mallet or a scrap of wood and hammer and holding the tenon piece firmly perpendicular, give the mortise piece a firm rap.
I'll just add one more HT strategy for parallelism: the router plane. You can use a router plane to get a very consistent tenon face because it references the stock itself. You get a piece of scrap, or another component (another rail, for instance) of the same thickness as your workpiece. Secure your workpiece to the bench, and secure the scrap piece right at the end of the tenon. THis gives you two good surfaces on either side of your tenon to reference from, and the router plane gives you a consitent depth from that reference. Thus, the tenon cheek is exactly parallel to the workpiece sides, and (assuming the workpiece faces are parallel) the two tenon cheeks will be exactly parallel.
I will say, though, that I very rarely actually do this. It's nowhere near as fast as using a 140 as fred suggested, or a shoulder plane, or even a float or rasp. However, all of these methods rely on your skill to get parallel faces. If parallelism is vital and you can't get what you want with one of these tools, try the router.
If you don't have a router, do an internet search for "old woman's tooth" and with a small chunk of wood, an old allen key, and a couple of simple bits of hardware you can have a very fine functioning router plane in an hour or so...
Lie-Nielsen #140 Block Plane
Unlike most of Lie-Nielsen's planes, this tool is quite different from the original Stanley plane upon which it is based. The basic plane is a skew-ironed block plane with a removeable side for rabbetting work. Lie-Nielsen has improved upon this design by adding an adjustable fence to allow the plane to be used as a fillester as well as a rabbet plane, and by lowering the blade angle to only 12 degrees. Precision machined from a manganese bronze casting with a cherry front knob. $199.95
__________________ I have a very low gag reflex - Woodma 1-18-08 Ain't that the truth - Bones 1-19-08
Interference fit in M+T - a query
- Bones 1-19-08
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