Shelves & Strength - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 06-10-2013, 05:05 PM Thread Starter
dlb
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Shelves & Strength

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The shelf is:
3/4" QS white oak
9 1/2" deep
32" long
The back for the shelf is:
3/4" QS white oak
3" high
32" long
Need to attach the back to the shelf where the bottom of the back sits flush w/ the bottom of the shelf.

(Similar to the above photo)
My question: What is the best method to attaching the two pieces together that will provide the greatest strength?
No bracing can be used, screws are O.K.
Thanks,
dlb
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post #2 of 9 Old 06-10-2013, 05:09 PM
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If you can glue, I would expect this to be the strongest method.

If you want to be able to disassemble, then cross-dowel nuts in the shelf and appropriate 1/4in screws from the back will be strong.

http://www.leevalley.com/US/Hardware...75&cat=3,41306
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post #3 of 9 Old 06-10-2013, 05:18 PM Thread Starter
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Dave,
I can/will use glue. My main concern is if the customer places items that are heavy on the shelf it may pull away from the vertical support. I was thinking about running screws thru the vertical member into the shelf after having glued them together.
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post #4 of 9 Old 06-10-2013, 05:30 PM
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Quote:
Originally Posted by dlb View Post
Dave,
I can/will use glue. My main concern is if the customer places items that are heavy on the shelf it may pull away from the vertical support. I was thinking about running screws thru the vertical member into the shelf after having glued them together.
Assuming the mating surfaces of the shelf and back are a good fit with no gaps without clamping, then a yellow glue joint e.g., Titebond I, II or III should be stronger than the wood.

You can easily reinforce with screws. Would help if the board for the shelf had any cracks.
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post #5 of 9 Old 06-10-2013, 05:33 PM
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Keep in mind that a glued joint is stronger than the wood itself. In other words, screwing the two items together will add little or no strength to the joint.

If I was making the shelf, I would use maybe three biscuits to align the joint.

My biggest concern is how you are attaching the item to the wall. Unless you go into the studs, that will be the weak point.

Howie..........

Last edited by HowardAcheson; 06-28-2013 at 04:37 PM.
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post #6 of 9 Old 06-10-2013, 05:54 PM
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I would run a 1/8" deep rabbet for the shelf to be let into the back (rabbet is in the vertical support.) I would machine a " spline into back edge of the shelf and into the center of the rabbet. Groove depth make 3/8" to both pieces. Cut a spline from hardwood (preferably cross grain, and if so could be several pieces) 11/16" wide. Use yellow glue and clamp it up.

You will likely only catch 2 studs (hopefully). If you are so offset to the studs that you can only catch one, use a toggle bolt for the other. Try to get two screws per stud. Don't use any screws bigger than #8, and it would be wise to use a small pilot hole so the stud doesn't split (if it's wood).






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post #7 of 9 Old 06-10-2013, 06:07 PM Thread Starter
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Quote:
Originally Posted by cabinetman View Post
I would run a 1/8" deep rabbet for the shelf to be let into the back (rabbet is in the vertical support.) I would machine a " spline into back edge of the shelf and into the center of the rabbet. Groove depth make 3/8" to both pieces. Cut a spline from hardwood (preferably cross grain, and if so could be several pieces) 11/16" wide. Use yellow glue and clamp it up.

You will likely only catch 2 studs (hopefully). If you are so offset to the studs that you can only catch one, use a toggle bolt for the other. Try to get two screws per stud. Don't use any screws bigger than #8, and it would be wise to use a small pilot hole so the stud doesn't split (if it's wood).








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What I see from your suggestion is an effort to to increase the gluing surface, correct?
Tage Frid uses that method and I am considering it also. As far as attaching to the wall that will be no problem as I do have 2 studs to fasten into. I'll use a couple of screws per stud and cover the hole w/ a plug.
Thanks!
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post #8 of 9 Old 06-10-2013, 06:16 PM
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Quote:
Originally Posted by dlb View Post
What I see from your suggestion is an effort to to increase the gluing surface, correct?
Tage Frid uses that method and I am considering it also. As far as attaching to the wall that will be no problem as I do have 2 studs to fasten into. I'll use a couple of screws per stud and cover the hole w/ a plug.
Thanks!
There's more to that joint than just increased glue surfaces. By virtue of the rabbet, there is that 90 corner that is fitted along the top edge of the shelf. It doesn't seem like much, but it will provide a stop for the shelf to resist tipping down. The spline will provide a very rigid right angle support.






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post #9 of 9 Old 06-28-2013, 08:36 AM
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Quote:
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Tage Frid uses that method and I am considering it also.
He doesn't use it anymore...he is deceased. You still have me.






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