Shelf pins for bookcase with long span/heavy load

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blueman wrote:

Ah, so! My goof!
--
It's turtles, all the way down

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in excess of 200 lbs. Using 4 pins per shelf gives a shear load in excess of 800 lbs. Putting an extra pin at the back centre of the shelf helps keep the sag to a minimum. The pins will not fail.

right? They also help support (if that's the right word) the hole and keep it from deforming. The part that fails is the wood. It gets possible tear out when load is applied.

and are good looking with the sleeves.

with holes 2" OC.
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snipped-for-privacy@mts.net writes:

I guess, if possible, I would prefer to avoid a back column of holes since it will be visible (even though pretty perhaps with the sleeves). The holes on the sides will be less visible due to a combination of the angle and the fact that the face frame will overlap the sides by about 1/2" or so.
I'm thinking that I will build without a middle back column of pins and only add later if sag seems to be a developing problem.
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Sleeves will definitely add tear out prevention strength to your shelves and are pretty cheap. I'd buy a small package of sleeves and use several to make a mock up side to see if they're visually appealing enough to you.
When it comes to installing them, instead of hammering them in place, I've found that you can make a neater installation by using a sleeve setting punch and a clamp to press them into place.
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Do you use glue to secure the sleeves or just assume a tight fit?
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Tight fit only. In over 20 years of using sleeves in plywood, softwood and hardwood, I've never had a sleeve come out or even noticed one start to come out. The pressure is sufficient to hold them. Also too, if I'm going to paint or stain or finish in any way, I do all that first with the sleeves being one of the last parts of the construction process. Even with slight splinters caused by drilling the holes for the sleeves, the outer, wider edge of a sleeve finishes off a hole very nicely if it is pressed hard enough into the hole to make it flush with the surface.
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blueman wrote:

Some points haven't been covered by other replies; first, in terms of stiffness, your double 3/4" plywood has the same stiffness as double 1/4" plywood with a center space (glued lightweight ribs or hardwood at the pin-stress points) of about 1.25 inch. Overall height of the sandwich is then 1.75 i nch... but there's a lot less shelf weight and cost.
Also, the pins are stressed downward at the face of the upright, BUT they tilt slightly and the pins actually press upward at their deepest point, so your load is carried on the surface area of (roughly) the width of the pin times half its depth in the upright. That is why a pressed-in collar is such a good idea (the area of the collar is larger, and if the tilt of the pin doesn't deform the collar, the useful area is doubled by comparison).
For heavy timbers, where stresses are near the material limits, pins aren't used; instead one makes a circular cut and presses a ring (like a pipe section) into it. The shelf depth would tolerate 3/4" pipe sections instead of little pins, and with suitable (hardwood) trim at the composite plywood endcaps, Forstner drill/routing a recess to hide the pin would be easy enough.
I've always hated high-stress points, like metal pins in wood, because age, accidents, and changes in moisture can crush the wood so easily. Even if it doesn't fail soon enough to catch in a test, it WILL fail.
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