Shelf pins for bookcase with long span/heavy load

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" plywood).

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)

Reply to
blueman
Loading thread data ...

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?

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.

Reply to
George E. Cawthon

Can I ask why you don't recommend the use of sleeves George? I've always used sleeves, both for added strength and neatness of appearance.

Reply to
Upscale

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?

Thanks

Reply to
blueman

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 o= n the shelf to get up from kneeling. I'm guessing that was only about 50 pou= nds of pressure on the shelf, but it was localized to a handspan near the pin.=

--=20 It's turtles, all the way down

Reply to
Larry Blanchard

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 th> I'm building a bookcase with adjustable shelves with a 46" span that

Reply to
Pat Barber

That's pretty big span

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.

-Steve

Reply to
Stephen M

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.

Reply to
blueman

Assume the pins are cheap grade 2 steel. That gives a shear strength 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.

A sleeve is a beautiful finish to any blank holes (adjustable shelves, 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.

The 3rd row should be in the back centre. They stay out of the way and are good looking with the sleeves.

Can't help on the Rockler jig. I use strips of peg board - the ones with holes 2" OC.

Reply to
cselby

Well, I plugged my dimensions into the "Shelf Sag Calculator"

formatting link
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. Width: 46" Depth: 12" Thickness: 1.5"

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

Reply to
blueman

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.

Reply to
blueman

"blueman"

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 object. 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 hole.

Dave

Reply to
Teamcasa

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.

Reply to
Upscale

Do you use glue to secure the sleeves or just assume a tight fit?

Reply to
blueman

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.

Reply to
Upscale

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.

Reply to
George E. Cawthon

You should have said the sides would be plywood! Sleeves would have to be metal at least an inch long which would be a pita.

Forget the pins and move to a different system if you stay with plywood.

Reply to
George E. Cawthon

Huh? If .06 is 1/16, 1/32 should be .03. - .12 would be 1/8 (actually .125=1/8).

Reply to
Larry Blanchard

Deflection is .06" over 46" while eye can recognize 1/32" per RUNNING FOOT, which would translate into about 0.12 (or 1/8") over the 46" length.

Reply to
blueman

Ah, so! My goof!

Reply to
Larry Blanchard

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.