Shelf pins for bookcase with long span/heavy load

Per your excellent suggestion in another post, I do plan to do a test.

However, how much would I gain in moving from say plywood sides to poplar sides? Would the resistance to pin tearout be significant enough to justify the significant premium for 1x12" poplar?

Reply to
blueman
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More generally, what type of wood would you recommend for the sides that would give good shear strength for the pins at an affordable price? I assume that I only would need the hardwood for the hole tearout so that 3/4" stock would be sufficienct since I could get additional stiffness by backing up the hardwood with a parallel piece of plywood side.

I am going to be painting the wood so I just need a wood that takes paint well. Also, I assume that since I am painting, it still makes sense to use 1.5" of doubled up plywood for the shelves (with poplar facing) and for other elements other than the sides holding the pins and the face frames.

Reply to
blueman

Almost any solid wood would do since you are going to paint it. Stay away from the very softest woods such as western redwood and cedar which you wouldn't normally consider. I've used ponderosa pine with no problems and that is probably as soft as any available to you. Any hardwood, including softer varieties such as Philippine mahogany would be fine but if you paint you probably want a tight grain. Personally, I would use solid wood of 1.5" thickness for the shelves. An alternative is to face (back and front) a 3/4" thick board with 3/4" x 1.5" or 2" strips (wide measurement would be vertical). The latter would provide about as much stiffness at the former and would essentially hide the pins.

I'm not a fan of painting book shelves. Just be sure that you use a paint that hardens well and has a high blocking rating (low blocking would mean that books will stick to the shelf).

Reply to
George E. Cawthon

I would also do the test with a small piece of good plywood. A 9 ply plywood ?might? survive you test

In my opinion you would gain a lot with solid wood. OTOH, I don't much like poplar. But.... depends on prices of different woods where you live. In choosing boards that are relatively clear and straight, the difference in prices of cheaper and more expensive woods is often slight. Where I live poplar is not much cheaper that much better woods. Again, though, in my opinion, it would be criminal to put paint on oak, maple, cherry, mahogany, etc, so poplar would probably be a good choice. Check the prices where you are at a real lumber store, you might be surprised at what you can get.

Reply to
George E. Cawthon

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?

Reply to
blueman

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.

Reply to
whit3rd

I haven't been following the bulk of this thread where you've indicated how much weight you're going to be putting on these shelves, but to be honest, what you're proposing sounds a little like overkill. If using pins with sleeves still sounds like it's going to fail on you, then you're not using a proper support system for the weight you have in mind.

Reply to
Upscale

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