WWA Info Exchange

Ok so even though I'm an experienced wood worker I still might get the dumb oops award here. For the past 3 days I. Have been planing and sawing my milled white oak in process of making 16 1" stair treads. Each tread is just shy of 12 wide and 54" long. I laminated several 3-4" wide pieces reversing the rings for each tread. Then glued and clamped. So here's my question; I decided not to use biscuits the lamination process. I was having trouble with my biscuit tool and finally just gave up and used copious amounts of yellow glue. The mating joints were all very good with no gaps (used jointer on all edges and tons of 3 any panel clamps. I know even these very hardwood thick treads are structurally strong but they will have to endure 200lb folks stomping up and down the staircase regularly. DO YOU THNK I SHOULD WORRY OVER NOT USING BISCUIT JOINERY? Thanks for your candid opinion.
Jim in Franklin, TN

IMHO, if you are not having trouble with alignment, I see no reason to worry about the biscuits.

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"To all those who work come moments of beauty unseen by the rest of the world." Norman Maclean

Many, many tests, to destruction, have shown that biscuits do NOT add any strength to a well machined glue joint. I built my treads in the same manner from 8/4 Euro Beech and haven't had a bit of a problem for going on six years. From the sounds of your other posts here, I suspect you're something of an accomplished wood worker so your jointing is most likely as good as one could expect.

Remember, the rule here is, no pictures, didn't happen (grin)

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Nullum Gratuitum Prandium

Cheers - Dennis

jimongee,

Biscuits are just a short cut to alignment, they don't add any strength.

My 2¢,
Tom

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"There is no path to peace, peace is the path."
Mohandas K. Ghandi

Tom,
I have never heard this. How can they not add any strength?
Teach me.
Clueless Zulu

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Zulu's website
http://www.jmelledge.com

Hey Zulu,

Both Fine Woodworking and Popular Woodworking have done destructive testing on biscuit joints vs edge glued and other joints. I can't link to the articles because of paywall blockage, but the gist is that, given the glue already bonds stronger than the wood, mortising the wood for biscuits, splines or dowels, in edge to edge glued joints, negates any advantage the biscuit might add.

In end grain to edge grain joints, dowels and biscuits are roughly equivalent, although Rockler maintains that dowels are better. Generally, I use either a fixed or floating tenon for an end to edge frame joint.

I haven't looked into strength added by pocket screws but I have used them in long edge to edge joints to aid in drawing the joint together, and alignment.

Cheers,
Tom

_________________
"There is no path to peace, peace is the path."
Mohandas K. Ghandi

To expand on the above ...
My opinion :

A biscuit, unlike a dowel or spline (which are solid wood), is comprised of chips that are compressed together (with heat? and adhesive?).
OSB is similar in nature.
The blade that cuts the slot for the biscuit excavates more original wood than the biscuit replaces. The remaining void is then filled with glue.
Though potentially gap filling, the glue (in and of itself) is not structural in any real sense.
So, in biscuit joining, you are removing solid stock and replacing with compressed chips and glue.

This is the way I view biscuit joining which may or may not be accurate or true.

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~Dan.

I've edge glued a number of boards, and often do destructive tests on examples. In each and every case I've tried, the wood failed before the glue joint provided 1) there was sufficient glue (doesn't take all that much) and 2) the joint wasn't compressed to the point of 'starvation'. I don't have any kind of test instruments with which to measure the amount of force required to break biscuited vs non biscuited joints but given that the wood itself is weaker than my glue joint, I don't bother with biscuits unless I have alignment problems.

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Nullum Gratuitum Prandium

Cheers - Dennis

I was taught the edge glued pieces should be doweled. A friend of mine who was a professional furniture maker told me that him and his partner didn't use dowels or bisquits except for alignment.................I didn't want to believe it. After reading a lot of articles and Bruce Hoadley's book Understanding Wood, I am totally in the "only for alignment camp" with dowels and bisquits.

I have been making furniture for 38 years (OH NO I SOUND LIKE AN OLD GUY< LOL) as an amateur, and none of my edge glued panels with or without dowels have failed, except a few that weren't jointed properly and required excessive clamping pressure.

BTW, if they don't fit together well, rejoint them and get it right before applying glue and clamps! Lesson learned the hard way.

My two pennies. Ron

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"To all those who work come moments of beauty unseen by the rest of the world." Norman Maclean