I'm building a bookcase with adjustable shelves with a 46" span that
will likely carry some heavy books.
To cover the load, I am making the shelves 1.5" thick (double 3/4"
I now want to make sure that the shelf pin setup I am using is as
strong as possible.
- Can I assume that all other things being equal, 1/4" pins will support
a heavier load than 5mm pins (since the diameter is larger)?
- Will using a "sleeve" in the shelf pin hole add strength and prevent
tearout from too heavy a load?
- Would adding a third parallel column of pins on each side support
*materially* improve the strength?
- Any other suggestions to maximize strength of a shelf pin setup?
(note: I would prefer not to add any intermediate supports)
- Finally, any feedback on the Rockler Shelving Jig? (it seems to do
the job, comes with self-centering bits, and is affordable)
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
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.
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.
I personally don't like the rails because they are more obtrusive.
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.
Do the sleeves add no strength advantages then?
I have torn out the 1/4" holes in plywood sides, but solid wood should be more
resistant. I don't know which you're using.
BTW, my shelves were only 30". I tore out the pins by bracing myself on the
shelf to get up from kneeling. I'm guessing that was only about 50 pounds of
pressure on the shelf, but it was localized to a handspan near the pin.
It's turtles, all the way down
Hmmmm... that's not too encouraging.
For the sides, I am also using double 3/4" plywood which is why I was
enquiring about sleeves. My thinking being that sleeves would better
distribute the force and prevent tearout.
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?
I would also do the test with a small piece of
good plywood. A 9 ply plywood ?might? survive you
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.
More generally, what type of wood would you recommend for the sides
that would give good shear strength for the pins at an affordable
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
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.
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
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).
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
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?
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.
I would consider maybe more support on the back sides
of the shelves. Maybe a small cleat placed a foot or
so apart the length of the shelf. You could use a small
profile on the cleat and it will not be noticed.
I also think 46" is really pushing the limits on a
Plywood is not the most deflection-resiting material as half of the plys are
going the wrong way to help. Solid wood will perform better. If I were you I
would try it out an see how much deflection wou get applying hand pressure
to the center of a test-shelf.
I think that is a fair assumption
Yes it would resiste the tendency for the hole to deform
By 50%.... 3 pins carying the weigh previously carried by 2.
You may not need to take any of these measures. The pins are not going to
sheer off. Try a test to see how much weight it takes to significantly
deform a hole. Just mock up something with a single pin in the proposed
material and put most of your weight on it. I bet it will hold up pretty
Well, I plugged my dimensions into the "Shelf Sag Calculator"
(www.woodbin.com/calcs/sagulator.htm) using the following parameters:
Species: Plywood, fir (only plywood choice)
Weight Load: 200lb, uniform load
Note: this seems generous given that per the note, they
claim that a fully loaded bookshelf weighs 20-25lb/foot.
Which for me would have given a maximum of 96lbs.
The resulting maximum deflection was 0.06" which is about
1/16". Again, according to the notes, the eye can recognize a
deflection of 1/32" per running foot, which would translate into 0.12"
in my case of a 46" span, again well within my tolerances.
For comparison, a "standard" 36" wide Eastern White Pine bookcase with
8" depth shelves under a load of just 25lb/foot would give a
deflection of 0.13" or more than TWICE as much as my design.
ALSO, I am going to be giving each shelf a front edge facing of
1.5x0.75" poplar which should add strength, I imagine.
Assuming that all my calculations above are correct, I am now most
worried about shelf-pin tearout which is why I was thinking that the
wider pin (1/4" vs. 5mm) and the sleeves might help
I have found that 90% of the time, one a shelf is installed, people rarely
move it. And if they do, its only a little bit to accommodate a taller
With that, I would only have a few adjustment holes in the general area
where the shelf is likely to be.
For very heavy load and thick shelves, I would use a 3/8" pin, set deep in
the side. To hid the heavy pin, I use a forstner bit and drill a 3/8 hole
in the side of the shelf and chisel out a notch in one side for installation
and removal. This hides the pin completely when in place.
As for the larger holes in the case, I cut 3/8 plugs and insert them in the
holes aligning the grain. If the ever need to be removed, I drill a small
hole in the end, insert a screw and pull them out for use in the now exposed
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