# Screwing into the side of 3/4" plywood



## hollallen (Jan 21, 2016)

I am working on a set for a play with a rotating stage. I am joining 2 circular 3/4" plywood sections face to face at 90 degrees for more stability. My question, however, involves connecting some 2" x 3" studs to the side to rotate. I plan to recess the stage area so that the stud fits flush to the side. I am not sure, however, what I would use to connect the stud face to the 3/4" plywood side. Any help would be greatly appreciated.


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## GeorgeC (Jul 30, 2008)

I cannot follow your words. A picture would be helpful.

George


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## Steve Neul (Sep 2, 2011)

Welcome to the club. 

I can't visualize what you are doing either. From the title, you can only have limited success putting a screw into the edge of plywood. It will work but has very limited strength.


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## TimPa (Jan 27, 2010)

you don't mention what it will be exposed to after in terms of structural needs. is someone standing on it, a flower vase,... that will impact the structural needs of the joinery. 

after a good solid bond (glues and screws) of the 2 ply discs, and a nice fitting cut-out for the 2x4, you could screw as mentioned (pilot hole is important to minimize splitting between the ply layers, and I would add an angle bracket to each joint for some rigidity. glue will help some.

what is use, and disc diameter? and 2x4 leg height? do you intend to support between the legs?


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## hollallen (Jan 21, 2016)

My apologies for the vague description..sort of hard to describe. I am not at my computer right now but will include an image in my nextbrepky in aboit an hour. Thabks for all your responses and help


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## hollallen (Jan 21, 2016)

*image examples*

I am at my computer now and I am including some drawings of what I was trying to explain. I have been working long hours on the designs for this set so my explanations may have been horrible...my apologies. 

Basically I would like a method of screwing into the side of (2) 3/4 plywood sheets through the stud at the bottom, used as part of a 16' revolving stage that is on 45 casters. I am trying to find a stabe way of doing this so the studs can be used to help rotate the stage since it will be rotated manually. There will be triangular blocks added at the bottom to secure the studs vertically. My thought was to cut into the sandwiched plywood on the edge to flush mount the studs to the sandwiched plywood edge, thus giving me some stability if the stud were used for rotating the stage.

Here are the image links:


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## EPAIII (Mar 31, 2012)

Your first drawing appears to be some sort of a wall. How does that fit in with a round, rotating stage? 

And the detail showing the stud and the plywood is not clear. You should show proper three view drawings (front, side, top) or a 3D one.


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## woodnthings (Jan 24, 2009)

*OK, let see if we got this right...*

You have a round stage 16 ft diameter. 
It has 3 vertical walls at 120 degrees apart.
You want to rotate the entire unit on casters ...45 of them.
You may want to use the walls to grab onto and rotate the stage.
You are concerned about making the walls strong enough so they won't deflect/break with the force needed to rotate the stage.
You are showing triangular blocks as reinforcing to keep the walls in place and vertical.

This all sounds OK to me.

Questions:
About what "center" does the stage rotate? Is it fixed or floating? Without a fixed center the stage may want to wander before it starts to rotate, adding more stress to the walls.
Will the casters be swivel or fixed? If you use fixed casters and mount them on the radius of the perimeter, radially, it won't wander as much and will have no choice but to rotate on center.
Your construction of the wall seems reasonable, but it relies on the screws mounting the walls to the platform. Will the screws be accessible from within the walls OR will the wall be covered with panels and cover them? Can you drive them at an angle, which will be stronger anyway and have them accessible?

You may just have to build it to find out what works best, but I think your ideas are sound. JMO.


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## hollallen (Jan 21, 2016)

*Sounds like you got it*



woodnthings said:


> You have a round stage 16 ft diameter.
> It has 3 vertical walls at 120 degrees apart.
> You want to rotate the entire unit on casters ...45 of them.
> You may want to use the walls to grab onto and rotate the stage.
> ...


Thanks for your input...nice to know I am not going crazy . To answer your questions, the center of the revolve floor has a 1" flange that that 3/4" pip, screwed to the floor goes over. All the casters are fixed and will be aligned in a radius around the unit.

I was really concerned about the sway of the walls so that is why I chose to use a stud on the end, cut to fit into the floor and bolted into place at the bottom. The walls will be screwed into the floor from the inside as well. Like you said I may just have to test it once up and see what works best.


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## EPAIII (Mar 31, 2012)

Now I understand. I have several concerns. 

1. The stud on the outer end of the walls seems to be divided in half by the horizontal that is about half way up. I would not do this; make it one solid piece all the way up. 

2. You appear to be fastening the wall on top of the rotating platform and all bracing is done on the top. If you can pass the outer stud down through the platform and use triangular braces on both sides of it on the underside, it will be a lot stronger. You seem to be using triangular braces on the top side and I would keep them if possible. If you can not run them through to the bottom, then I would step up to 2 x 6s or even 2 x 8s for those outer studs to give the wall a better foot and I would fasten the bottom ends of those outer studs with lag bolts coming up from below the deck. Use large washers on those lag bolts so they do not work their way into the deck wood and loosen (standard washer plus a fender washer or two on each bolt). And if you were thinking of using plywood for those diagonal braces, it would be better to use 1 x 12 lumber, cut diagonally, instead. 

3. I would add some wide 1 x lumber across those outer studs at the top, flat side up/down. 1 x 10s or 1 x 12s would be ideal. Fasten them to the top plates all along their diagonally cut edges and they will add a great amount of stiffness to the whole assembly. If it still wobbles when you turn it, you could add a second one a bit further inward. If those would be too visually offensive, you could use some wire cables in an X fashion from the outer ends of the walls to about the half way point, again on the tops of the walls so they are completely out of the way. Tension them with turnbuckles. This should make the assembly very stiff and it should not be a problem to turn by hand. Be sure to solidly connect the three walls top and bottom, where they meet at the center. 

4. You definitely should consider a center pivot. But with all those wheels, it may not be absolutely necessary. In any case, how easy it turns is a major consideration. Use good quality wheels, preferably with ball bearings. The larger their diameter, the better and they should have a hard tire, not a soft or inflated one. Less friction that way. Be sure they are all mounted in a tangential manner so they are all rolling in the proper circles. Keep them in the outer half of the radius as they will have to slip more as they approach the center. 

5. As for using screws into the end of plywood, I would not count on that for any holding power.


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