Greg, I participate less and less these days in instructional areas unless
it is with other professionals. I have found that most Google educated fol
ks find their level of practical experience to be much more valid than my 4
0 years of trades work, so I have nothing to say of value. But... I get a
charge out of you because you seem honest, sincere, ready to learn and impr
ove, and are already on the road of being a great contributor. You are just
a bit farther down the road (on the newer side!) than most of us here.
Enough of that.
You can put the frickin' biscuit discussion to rest here:
(This is what happens when you let engineers have too much time to figure o
ut a problem).
It concludes definitively that biscuits add strength in different kinds of
joinery, and provides the data to back it up. It discusses the use of mult
iple biscuits, compares biscuits to tenons, etc. It discusses the use of bi
scuit on certain types of joints, concluding that it adds strength in just
about all applications. In some cases it adds a great deal, in some cases
not so much.
Aspects not discussed in the abstract are the importance of keeping your bi
scuits clean and dry, not using broken biscuits, and it only touches on glu
ing technique. All information readily available, so no mysteries there.
I used to have a great .pdf somewhere that was generated by an engineer's g
roup to study the usefulness of the biscuit joint in modern furniture manuf
acturing techniques. It showed a great amount of comparative data that had
a single tenon vs. two biscuits, then large tenons vs. three biscuits, and
so on. (That is in the above linked abstract, too.) Interestingly, multip
le biscuits are quite strong, and in woodworking they seem to be good enoug
One of the pitfalls of being self taught or starting the road of being a de
signing woodworker is "over engineering" your work. This is usually due to
lack of practical instruction from a trusted source, lack of training, or l
ack of experience. As a professional that makes money with their woodworki
ng efforts, time is money so the key is to make the project strong enough t
o do its duty, and build it well enough to last for years if that is the du
ty cycle you are after. As a home craftsman enjoying their weekend, it is
easy to get caught up in all the hoopla about the joining techniques of the
old craftsmen and then further discuss how well their efforts lasted.
When I was doing a lot of refinishing, I was surprised just how simple many
joints were that I studied. Simple joints that provide plenty of glue sur
face (I was bowled over and delighted to see Karl's work included half lap
joints, as I was embarrassed to tell him I did that!) that can be held toge
ther with a couple of 23 ga pins until dry hold up fine. Joints that were c
leverly constructed to hide mechanical fasteners, etc. are great.
Read that abstract and you can see the value of multiple biscuits per joint
when attaching edge to side grain wood. The other study that I had but ca
nnot find included multiple biscuits in joints because they found the speed
and accuracy of biscuit placement was quite good, along with its easy repe
atability made multiple biscuits a good choice for a joining wood.
The abstract concludes with a bit of a tongue in cheek dissertation using a
gorilla as a metaphor for all the guys that want to be able to stack anvil
s on their pine magazine rack they built for their bathroom...
Keep at it! You do some nice work, Greg.