Need opinions

[Lee Schierer]

I'm building a book shelf to go on the wall above the desk I just made for our home office. The material is Hickory. Here's my question:

Would the bottom shelf be strong enough if I attach the bottom board to the vertical pieces with 2-1/2" screws going up through the bottom board into the vertical pieces. I would probably put 3 -4 screws at each location. The board along the back edge of the shelf will be attached to the studs in the wall. This would allow the fasteners to be hidden with plugs. I don't expect the shelf to ever be fully loaded with books.
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The screws would be GRK #10 x 2-1/2". I would drill pilot holes to avoid splitting the Hickory.

My other design thought would be to make 3/8" x 3/8" rabbet on each end of the bottom self and set that into a 3/8" dado in the two end pieces, but that would put the screws on the side of the vertical pieces where they would be more difficult to hide, even with plugs.

[Jerry Miner]

Lee-- I'm not a fan of screws into end-grain, as they don't hold that well over time. Hickory is pretty tough, though, so it could work. IIWM, I'd be more inclined to run the sides down past the bottom and use dowels, Dominoes, M&T, or the rabbet/dado joint you suggest-- or even screws with "decorative" plugs to cover (screws here are not relying on pull-out strength to carry the weight, only shear strength-- of which they have plenty). I would use dowels or Dominoes at the center divider, too.

[Andrew Seemann]

Honestly with hickory, you probably can just use the screws, but don't drive them in at 90 degrees, do more like 75 degrees and and not all in the same direction. That way you get some side grain (kind of like a pocket screw) and they can't pull straight out.

[Osvaldo Cristo]

I'm building a book shelf to go on the wall above the desk I just made for our home office. The material is Hickory. Here's my question:

Would the bottom shelf be strong enough if I attach the bottom board to the vertical pieces with 2-1/2" screws going up through the bottom board into the vertical pieces. I would probably put 3 -4 screws at each location. The board along the back edge of the shelf will be attached to the studs in the wall. This would allow the fasteners to be hidden with plugs. I don't expect the shelf to ever be fully loaded with books.
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The screws would be Spax #10 x 2-1/2". I would drill pilot holes to avoid splitting the Hickory.

My other design thought would be to make 3/8" x 3/8" rabbet on each end of the bottom self and set that into a 3/8" dado in the two end pieces, but that would put the screws on the side of the vertical pieces where they would be more difficult to hide, even with plugs.

We have in the library bookshelves made 25 years ago. I had on the occasion a number of books to bring to our (then) new home and just a very limited amount of time to construct something to house them, so I went to a "temporary" solution of very simple book shelves using 20 mm mahogany veneered high quality plywood. I decided to use only screws. Each shelf is 732 mm long (near to 29") and supports something between 25 to 30 kg of books. Only two 45 X 4.5 mm (1 3/4") wood screws support them from each side. No glue. No grooves. No sagging or other problem at all after 25 years... so they turned my "definitive" solution. I have 48 of such shelves fully loaded. (bellow I included a few pictures of them)

I am not sure how it would work with solid wood, Hickory in particular as my experience is limited to that plywood panels.

All the best,

[James Pallas]

Whenever I have doubts in that situation I drill holes perpendicular to the screw holes an inch above the bottom and 3/4 of the way through the vertical piece from the inside, easier to hide. Glue a dowel in the hole. Than drill your pilot hole through the bottom and the dowel. It works like a bed bolt somewhat. In any case it's not going to pull out. And not likely to split the vertical piece.
Jim

[John K Jordan]

Would the bottom shelf be strong enough if I attach the bottom board to the vertical pieces with 2-1/2" screws going up through the bottom board into the vertical pieces. ...
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I've built several suspended shelves exactly like that. This one over the door in the lathe area of my shop has been been up now for several years, built of 3/4"x7" shelving pine. I have stored heavy chucks on it. So far, no students or visitors have been harmed by the making and use of that shelf. I suspect hickory should be great unless you filled the shelf with gold bricks.
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I just checked - I have four deck screws into the end grain. I drilled holes for the screws, of course, and sized the holes carefully. I also used glue just for fun but I don't expect it to be too effective.

I didn't know about it at the time, but if doing this today I'd put this stuff in the screw holes before fastening: https://www.amazon.com/Schluter-Kerdi-Grey-Sealant-9-81OZ/dp/B0057GJ99A
The guy who did the tile in our new shower told me about this stuff, a silane-modified polymer bonding compound. I don't know exactly what that means but I know it's incredible everywhere I've used it. Expensive, though.

The dowels James mentioned would make it very strong.

JKJ

[Derek Cohen]

I agree with angled screws. Think of them as creating the same mechanical joint as a dovetail. Use a similar angle, and do so in sets of two screws.

Regards from Perth

Derek

[Wayne Lomman]

It will be solid as a brick house. I have done similar many times with no failures. Skew the screws if you want to. Cheers

[Prashun Patel]

If you do dados you would not need screws if you glue it.

[Mark Hennebury]

Murakoshi Seiko style connector bolts. I have used them for more then 20 years, they have many different styles and finishes and sizes. Incredibly strong, very simple and quick to install.

The cross-pin connectors are available in a variety of lengths and colors, and the cross-pins are a available in different lengths as well. They also have many other types of connectors, press-in, screw-in
Lots of different companies make them. you can get them at Lee valley and on Amazon.

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[Peter Kelly]

https://i.imgur.com/SqL1RTB.png

[Rich Aldrich]

I just built a few shelves similar to this. All end grain on the shelves were rabbit fit at the top and bottom and datto groove for the center shelf. For fastening, glued and used triple coated deck screws were used. It is stronger if horizontal boards are full length unless you datto groove - avoid butt joints.

My understanding is that biscuits offer no structural support - only use biscuits for alignment purposes.

[Lee Schierer]

Just to clarify the back will be open. I want to hide the fasteners. The top and bottom will be one piece. The middle shelves will be adjustable. The screws will go into end grain of the vertical pieces.

[Brian Holcombe]

I would rabbet this. Better still a lock miter would do the job well in all corners and manages to look nice while doing so.

[Andrew Joiner]

Just to clarify the back will be open. I want to hide the fasteners. The top and bottom will be one piece. The middle shelves will be adjustable. The screws will go into end grain of the vertical pieces.

Lee, why not do a quick test on scraps? I bet dovetail angled screws or even 90% screws will be proven strong enough for your needs.

[Lee Schierer]

I just finished the bookcase. What I decided to do was get as much height as I could so I rabbeted the bottom board into the sides and secured the joint with glue and screws. The top is sits on top of the sides and is held on with screws and glue. The center divider fits between the top and bottom boards and is held in place with screws. The stringers top and bottom are attached with pocket hole screws and glue. All the screws were counter bored and hidden with hickory plugs that were sanded flush. I am in the process of putting the finish on as I write this. I plan to attach it to the wall with long structural screws in the studs.

[Steve Demuth]

The holding force of a woodscrew in endgrain is reckoned by the people who think about such things to be about one half to three quarters of the same screw, same wood in lateral grain, assuming no splitting. For hickory, for a standard #10 screw with 2" of actual thread, that works out to about 2500 lbs, per screw. GRKs probably have at least twice the holding strength of standard wood screws.

The screws are not going to pull out unless the wood splits. Their heads will pull through the lateral grain of the shelf long before he shanks move in the endgrain. If you've ever done demolition of screwed-together framing, you've seen that in action - a screw head will pull through 1 3/8" of framing long before the threads of a framing screw will pull out of most lumber.

Pull-through resistance on hardwood is going to in the hundreds of lbs per screw.