"George E. Cawthon" writes:
blueman wrote:
"George E. Cawthon" writes:
Why don't you use the standard metal shelf support rails (the ones
with slots that use metal V support clips) that are dadoed into the
shelf sides sides?
I personally don't like the rails because they are more obtrusive.
Sure 1/4" will support a heavier load than 5mm. 1/4" is about 6.4 mm.
But you are talking about shear strength. I can't imagine how much
weight a shelf would need to shear off four 1/4" pins (dowels).
Probably more than one could put on a shelf using 12" high books.
Sounds like I will be OK with the 1/4" pins (though I have some sets
of books that as big as 14"x12"_
My question was not so much about breaking the pins (which I imagine
would be hard to do) as about tearing out the hole.
What I really wanted to know is whether the 1/4" pin system is
significantly stronger than the 5mm system to justify the bigger and
more obtrusive 1/4" holes.

No, don't use any kind of sleeve. just make sure the pins are snug in
holes that are accurately at right angles to the shelf side and are
drilled to a depth of 1/2" and the pins extend about 1/4" from the
surface.
Do the sleeves add no strength advantages then?
Thanks

I suggest you make a simple test shelf. The shelf only has to be 3-4
inches high. Use the same thickness of materials sides, pins, and
shelf that you want to test. The construction can be very simple just
two uprights braced and nailed so they won't spread out. Knock it
together then have one person stand in the middle of the shelf
(150-200 pounds), then try two people near each end (300-400 pounds).
If the pins break you only fall 3-4 inches.

Please note that you want the shelves to fit between the uprights with
as little extra space as possible, just enough so that you can move
the shelves.

BTW, if you keep books on the shelves, you will never see those metal
rails, and even if you don't they won't be obtrusive if you paint them
the same color as the wood.

Just did the test today.
So far, I put my own weight (~200lbs) on the middle and then on each
of the ends and did some light bouncing without any tearout. I will
add more weight (i.e. more people) later.

I built the test stand with off-the-shelf Home Depot 3/4" birch
plywood but expect to use higher quality stuff for the real bookcase.

Also, I was thinking that I could further reinforce the holes by
"painting" the holes first with a low viscosity epoxy (the type that
is used as a wood hardener) and then inserting the pins. This should
hopefully have the dual effect of hardening the wood surrounding the
hole and also anchoring the sleeve to the hole so that it spreads the
transferred weight more broadly to the surrounding wood.

Does the above sound like a good idea?