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Discussion Starter · #1 ·
Hi everyone,

I was just wondering if anyone has ever had any problems with MDF warping when they use it in hot temps? I am making an entertainment unit in my garage which is really hot. I have glued and dismantled it( with a hammer I might add! coz im getting rather pissed with it.) twice already. the thing is, I glue it and screw it, measure and make sure its all level and when I come back to it in a couple of days it seems to have warped and be crooked and unlevel. could this be because of the heat in the garage? or do I just realllly suck at woodwork!. :censored: im thinking of giving up but I have really enjoyed doing it when its all goin smooth. also is there anyway I can try to fix it once its warped rather than take it all apart and start again? it the uprights that keep going crooked. either they all lean to the left or all to the right. the picture is from the first attempt. it wouldn't matter so much but I want to put doors on each end cubby and they wont fit because its not straight. this is my first woodworking project so any advice would be great. Furniture Room Table Floor Shelf
 

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Discussion Starter · #4 ·
I had thought that, but I wanted an open back on the unit. do u think it would make it any better if I just put panels in the back of the end sections and left the middle shelves backless? is racking the term used for the problem? I am putting a solid matai top on it, maybe I could "force" it into shape when I attach the top? lol.
 

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MDF warps in heat, to counteract the only way to stop it is constructing it in cooler temperatures.. You can include more supports but that may affect your design and still won't guarentee no warping..
 

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where's my table saw?
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MDF doesn't "warp"

I had thought that, but I wanted an open back on the unit. do u think it would make it any better if I just put panels in the back of the end sections and left the middle shelves backless? is racking the term used for the problem? I am putting a solid matai top on it, maybe I could "force" it into shape when I attach the top? lol.
If by warp you mean "sag", yes that would be your problem.
The center shelves are too long and unsupported. A back panel would help and then the rear edge of the shelve would be supported. The front edge will still sag unless you put in a few dividers between the shelves to carry the load/weight to the rear edge. Lots of physics involved here, so you can just wing it and have good results, but I admire your effort regardless.

If all your frame work is MDF that's another issue. It just isn't very strong compared to real wood. The long horizontal pieces of the frame have little or no strength. I assume the thickness of the MDF is 1/2" right? that's another issue. If the frame work is 2 X 4 then that should be OK, but the span is still to great for it not to sag... some.

This was a learning experience. You can fix this one or you can start over using some Poplar , Pine or hardwood for the frame pieces. Use plywood for the back 1/2". Use 3/4" solid wood or plywood for the shelves and sides. You can make the unit with 3 components, 2 ends and a center section. Then screw them together afterward to look like one unit, easier to manage and much stronger. Keep the span/length of the shelves under 30" to prevent sagging. Use a back panel when ever possible to prevent "racking" that means collapsing like a cardboard box would.

More advice, go to a store that carries shelving like this. Look and see how it's made. See if the material is real wood, plywood or particle board covered with a skin, MDF. The better units will use hardwood and plywood for construction. See how the shelves and sides are attached. Are their fasteners or dados and rabbets? If you don't know what those terms mean, look up "wood joints" on the web. http://woodworking.about.com/od/joinery/tp/JoineryHub.htm

Best of luck to Ya. :yes:

http://video.about.com/woodworking/How-to-Build-Utility-Cabinets.htm
 
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Don't trash your project. It only needs a few touches. Constructed as it is, it's prone to racking. that's where the cabinet can sway left to right and back. To stop that, you need to attach the verticals to the horizontals, so they can't move on each other.

Installing backs can do that. The back can be as minimal as ¼" plywood. The span for the shelves is a bit long, but you can insert dividers in there pretty easy. You can toe nail the front and back of them into the shelves, and use glue.

You can also add a face frame. That's just a solid wood framework that is attached to the front edges. That would help stiffen the whole cabinet. If you have set it on an uneven floor, the cabinet would likely rack just from sitting. When working on it set it on its back so the face of the cabinet is up. Face frames can be 2" plus or minus wide by ¾" thick. Just glue and fasten from the front.

The cabinet would benefit from a loose toe kick, which is just a boxed out frame with cross members. I would make that out of ¾" plywood. It can be any height, and a reference to height would be a kitchen cabinet toe kick which is usually 4" high.






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where's my table saw?
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terms

Warping, sagging and racking are all different issues, some of which are related. Warping is a condition of the wood where it twists or bows. Sagging is a result of having no horizontal support on the shelves and just relying on the material itself for strength. Racking is a result of having no vertical restraint, usually a lack of a rear panel. Open shelves are prone to racking without a rear panel and sagging shelves.
Face frames can add some support to the front edges of the shelves, if the span is not too great and can prevent racking to a degree, but a rear panel is best.

You need to be specific about exactly what condition you are having, but from the photo sagging and racking are the obvious ones. Warping does not seem to be an issue here. :no:
 
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Discussion Starter · #10 ·
I would say it is racking. after reading all the helpful things people have replied with I think I will try and add a back on it and put a divider in the middle section of shelves. its worth a crack! thanks :)
 

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Discussion Starter · #11 ·
Just used the website. its so cool! my shelves should be okay as long as I don't put over 6kgs on them. thanks for the link. its now saved to my favourites for future reference. cheers! :)
 

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Way to stay with it :)

To me woodworking is like golf. A bad day puts me in a bad mood, a good day and I'm in a great mood. I shoot for the latter but usually end up with a decent day, and then my daughter turns it into a great day :)

Good luck!
 
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