Help with steel rods for heady duty bookcase.

Waste of steel. If you simplly insert a spacer board midshelf that runs from the top of shelf N to the bottom of shelf N+1, it'll take the center-of-shelf stress down to the base (and it won't rust). Even cheap wood would work, you can stain it black so the hickory shows to best advantage.

Steel rods horizontally are floppier than wood, won't be much of a brace. The use of a steel C section at the back of each shelf might be better (it's the metal at top edge in compression, and bottom edge in tension, that makes rods less effective than C sections or the old I-beams.)

If there's a plywood back on the unit, drill for a few pegs to shift the sag stress to that.

Or, you could make two 24" shelves from the 48" boards. If you must perforate the shelves, a wood dowel or two will keep those spacers in their place.

Will this prevent any sagging at least for 10 years, if not 20+?

Basic idea. I am building a bookcase primarily of hickory for my reference library. The library consists of the Oxford English Dictionary, Great Books of Western Civilization, various books on programming languages, ...

Calculations of load. Many of the shelves will be loaded with books for full 4' length and books of 12.5 inches tall by 10 inches wide. That gives a total volume of 6000 cubic inches or 98322.384 cubic centimeters. Based on the specific gravity of paper of 1.2 grams/cubic centimeter, that yields a load of just over 260 pounds. Allowing for 10% safety margin, that is about 290 pounds load per shelf.

Design: The shelves will be .75" x 11.5" x 48" hickory boards. Under the back for support will be a .5" x 1" x 48" (w x h x l) board. The sides will use standard metal shelf braces. I wish to drill two 3/8 inch holes the full length of the shelves, one in the middle and one an inch back from the front and insert 3/8" diameter stainless steel rods for further bracing.

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Horizontal 3/8" rods won't prevent sagging for 10 seconds, even if you could magically drill 48" deep without breaking out through the face of the shelf. I just went down to the secret laboratory, clamped one end of a 3/8" x 3' steel rod in the milling machine vise and deflected the other end 4" with my little finger. All types of steel deflect about the same distance under the same load, regardless of their hardness.

What you described works in concrete bridges because the steel rods are in the bottom edges of beams of considerable height, and they are tightened to resist a pure tension load, not bending.

My heavily loaded wall of book shelves are of 1-1/16" thick x 9" wide red oak with supports 30" apart, and no sag is visible when sighting down them. I sawed the logs into 1-1/2" planks hoping for 5/4" finished thickness, but they cupped during seasoning and 1-1/16" is where the planer cleaned up both sides of most of them.

The simple fix is to insert upright supports in the middle of the spans. Mine are simply a friction fit and none have shifted.

What braces the bookcase against tipping sideways?

You may have some problems with drilling 3/8" holes 4 feet deep and round rod is not particularly stiff. I wonder whether a different solution might not be simpler and, perhaps, stronger. For example 3/4" angle inlayed on the front edge of the shelves. Or even 3/4 inch flat stock fastened to the front edge with multiple fasteners. One assumes multiple fasteners along the rear of each shelf to the 1" rear of the case.

Under the back for support will be a .5" x 1" x 48" (w x h x l) board.

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Your posting suggests that you have no hands-on experience with the structural limitations of wood or metal. We all started there. The good suggestion of doweling intermediate vertical supports, for example, requires more than beginner skill at woodworking to make the holes align, and "standard metal shelf braces" includes many types that would be inadequate for your design load.

Are you planning to build this yourself?

It's not so much that the rods are stiff - if you use BOLTS and tension them against the shelf you mightbe able to significantly increase the bending strength of the shelf - but "gun drilling" a 4 foot shelf is going to be something of a problem, me-thinks.

A 3/8" hole through the middle (if you can even get it in the middle) of a 3/4" piece of timber is going to leave only 3/16" above and below.

No matter how strong and stiff the steel is, the timber shelf will break away from the steel as soon as you load it up.

CH

It's not so much that the rods are stiff - if you use BOLTS and tension them against the shelf you mightbe able to significantly increase the bending strength of the shelf - but "gun drilling" a 4 foot shelf is going to be something of a problem, me-thinks. ==================================================

The metal rods under the steps of a wooden step ladder are good examples of this.

On 5/20/2020 8:55 PM, Jim Wilkins wrote: ...

Neat!

On 5/20/2020 8:55 PM, Jim Wilkins wrote: ...

Neat! ================== "This calculator can also be used to measure beam deflection. Because beams are typically positioned on edge, use “thickness” to represent beam depth and “depth” to represent the thickness of the beam. The shelf span parameter represents the beam span."

snipped-for-privacy@gmail.com on Wed, 20 May 2020 15:33:51 -0700 (PDT) typed in rec.crafts.metalworking the following:

Steel rods will bend.

If you don't want the shelves to sag: first option (IMO)would be center supports. Don't have to be thick, just transfer the weight from the top to the floor.

Other option I would suggest is to either channel or angle stock attached to the front. You could even make the channel OD the same as the board thickness and rabbit the edge. Much more rigid than a rod. Also, you don't have the problem of trying to drill 48" deep six to eight times, without the bit ever wandering out the side. Not sure if they make ship augers (the sort which has no pilot screw on the tip) that length, but you can weld a 4 foot rod on the end..

OT3H,I'm not sure that hickory will need reinforcing. But if there is any bow in the boards, make that the "up side" so that any sagging will flatten the shelf.

And there's the critical issue.

IMHO, I'd go with adding a center divider on all shelves, to transfer load to the floor. Doesn't have to be a thick piece, could be 1/4 ". Or you could get some tall books from a thrift sore, and wrap the cover around a board, so that you don't have a visible support.

"Jim Wilkins" snipped-for-privacy@gmail.com on Wed, 20 May 2020 20:55:16

-0400 typed in rec.crafts.metalworking the following:

Neat. Now to find out what the shelves I have are made of, so I can retro calc their deflection.

{I have some Ikea Billy book cases. The wider shelves have sagged visibly over the last fifteen years, but I can't just flip the shelves so that they flatten. They work, and I've other things higher on the priority list. Like fining space for the rest of the books.}

That backboard. In the last move, the press board backs fell out of mine, but that's okay, the shelves are from wall to all, so there's no room for them to lean. Unless the whole place is out of kilter, in which case, those cases will fit in just fine.

There is particle board on the list, but there's a bunch of varieties (who knew).

I think you'll find the sagulator only tells Young's modulus sag for flakeboard, it ignores the long-term moisture induced bowing that you see. That depends entirely on the glue used (so it's unpredictable). Even the cheapest white woods are better shelving.

Bob Engelhardt snipped-for-privacy@comcast.net on Thu, 21 May 2020

18:02:12 -0400 typed >> Neat. Now to find out what the shelves I have are made of, so I

Its one of those "Now that you mention it, it is so obvious." items.

Yep. OTOH, It came in a box, I could put it together without power tools ... "it worked". And that is the basic question: how much time and effort is it worth to DIY, vs buy one in an box vs buy one already made?

Yep. OTOH, It came in a box, I could put it together without power tools ... "it worked". And that is the basic question: how much time and effort is it worth to DIY, vs buy one in an box vs buy one already made?

"Jim Wilkins" snipped-for-privacy@gmail.com on Fri, 22 May 2020 17:56:03

-0400 typed in rec.crafts.metalworking the following:

When I have the time. I have a couple sets of shelves (One for my clothes, the other to hold "stuff" in the shop), knocked out of the boards from a shipping crate. no real attempt to finish either one. "they work." But the things I'm intending for the wife, those will get more care in the fit and finishing.

When I have the time. I have a couple sets of shelves (One for my clothes, the other to hold "stuff" in the shop), knocked out of the boards from a shipping crate. no real attempt to finish either one. "they work." But the things I'm intending for the wife, those will get more care in the fit and finishing. pyotr filipivich

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I discovered that the columns of a set of plastic shelves I bought have the same 1.66" OD as 1-1/4" plastic electrical conduit, so I used some to raise the lowest shelf off the floor.