I am building an assembly table and plan to use 2 sheets of 3/4" MDF topped with a sheet of 1/8" hardboard. This will be a 4'x8' table that will have 3 full length stretchers supporting the top. The legs and stretchers were made by laminating 3.5" strips of 3/4" ply so I believe they will hold just about anything I want to put on them. I have never used MDF in a project and just wondered if I might need to add a 1/2" plywood to the top under the MDF??
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have you considered building a torsion box for your top? Check out The Wood Whisperer for ideas on building one. plenty strong, and sure to remain flat.
M
McRabbet
Barry,
Peter makes an excellent recommendation because MDF has a tendency to sag by itself over a broad span. By building a torsion box (a skin of MDF on each side with a grid of blocks froming the interior), you will have an incredibly stong structure. One of the best examples I've seen here is this well-documented thread by Alan in Little Washington. He provides good step-by-step guidance on his very strong and versatile table.
Peter makes an excellent recommendation because MDF has a tendency to sag by itself over a broad span. By building a torsion box (a skin of MDF on each side with a grid of blocks froming the interior), you will have an incredibly stong structure. One of the best examples I've seen here is this well-documented thread by Alan in Little Washington. He provides good step-by-step guidance on his very strong and versatile table.
For the frame you are building, I think you would be good. Wouldn't it make more sense to have two full length stretchers and a couple of cross members?
I made a similar frame for a solid core door awhile back but I made mine out of some douglas fir construction lumber I had. I doubled the legs and put locking casters on it. It has been a true joy to use and the fact I can move it easily is a BIG plus.
The torsion box suggestion is a good one that if you can accommodate and do I would strongly recommend.
Regardless of what you decide, I think you have it!
I made a similar frame for a solid core door awhile back but I made mine out of some douglas fir construction lumber I had. I doubled the legs and put locking casters on it. It has been a true joy to use and the fact I can move it easily is a BIG plus.
The torsion box suggestion is a good one that if you can accommodate and do I would strongly recommend.
Regardless of what you decide, I think you have it!
The torsion box idea is a good one but I'm afraid a little over my skill and equipment level at the moment. I don't have or have yet to build a cross cut sled and am still using the pitiful miter gage that came with the saw.:BangHead: Remember I'm still aspiring to be a novice. I still have lots of work to do on my measure once and cut twice mentality. But alas I am trying...
Making any table perfectly flat and level will be a challenge since the floor in my shop has a good many dips, low and high spots. So all I'm really after is a good sized table that is mostly flat and level. The table I have planned has 3 stretchers to span the 4' top.
My plan is to screw the 2 sheets of MDF together in case I need to replace one and use contact cement at stragetically placed intervals to attach the hardboard so I can remove and replace it.
The real reason I'm building this table now instead of more needed shop jugs like a cross cut sled, table saw extension table, band saw extension table or supports, and what ever else I need and just don't know it yet is because I bought a pocket hole jig and wanted to use it...:gar-La;
I think I'll try it as designed and if it doesn't work like I had hoped its only wood and I can get more. Thanks for the tips and Bas that is a cool site that I saved in my growing book mark list.
Making any table perfectly flat and level will be a challenge since the floor in my shop has a good many dips, low and high spots. So all I'm really after is a good sized table that is mostly flat and level. The table I have planned has 3 stretchers to span the 4' top.
My plan is to screw the 2 sheets of MDF together in case I need to replace one and use contact cement at stragetically placed intervals to attach the hardboard so I can remove and replace it.
The real reason I'm building this table now instead of more needed shop jugs like a cross cut sled, table saw extension table, band saw extension table or supports, and what ever else I need and just don't know it yet is because I bought a pocket hole jig and wanted to use it...:gar-La;
I think I'll try it as designed and if it doesn't work like I had hoped its only wood and I can get more. Thanks for the tips and Bas that is a cool site that I saved in my growing book mark list.
I built my torsion box assy table without a cross cut box, just ripping the MDF core pieces in long lengths then using just a mitre fence for the cross cut. The cross cuts don't have to be "within a knats" to work properly. It is more important that the top and bottom faces of the core pieces are parallel. I used 1/2 mdf for the top and bottom and over a 5' x 3' table it sagged just 0.006".
Barry,
If you are making it as just an assembly table, I would still try a torsion box style, But if you are also going to use it as a workbench go with your idea and as Travis said try cross members also for support. For the top use 'tempered' hardboard instaed of regular, it's just a tad more expensive and much harder.
Good luck,
Jimmy
If you are making it as just an assembly table, I would still try a torsion box style, But if you are also going to use it as a workbench go with your idea and as Travis said try cross members also for support. For the top use 'tempered' hardboard instaed of regular, it's just a tad more expensive and much harder.
Good luck,
Jimmy
Barry,
You can make very accurate crosscuts with your miter gauge by using a short auxillary fence clamped to the front of your rip fence set like a stop block to your exact width. Just make sure the piece you're crosscutting is not touching your rip fence or aux fence during contact with the blade or it could kick back on you. Put some self stick sand paper on your miter gauge fence and your piece won't move while it's being cut.
I have a double 3/4" MDF top on my assembly table with a web frame and it is coated in 5-6 coats of poly sanded between coats and then waxed. It needed to be filled with putty in a few low spots and sanded down in a few high spots but it is very flat and glue does not stick to it. I take care not to pound on it or drive screws or nails into it and the poly coated MDF has held up very well.
My advise is to make it as small as you think you can as it seems to get bigger each week and occupies valuable floor space. If you can make it small enough to be stored under another bench do it.
You can make very accurate crosscuts with your miter gauge by using a short auxillary fence clamped to the front of your rip fence set like a stop block to your exact width. Just make sure the piece you're crosscutting is not touching your rip fence or aux fence during contact with the blade or it could kick back on you. Put some self stick sand paper on your miter gauge fence and your piece won't move while it's being cut.
I have a double 3/4" MDF top on my assembly table with a web frame and it is coated in 5-6 coats of poly sanded between coats and then waxed. It needed to be filled with putty in a few low spots and sanded down in a few high spots but it is very flat and glue does not stick to it. I take care not to pound on it or drive screws or nails into it and the poly coated MDF has held up very well.
My advise is to make it as small as you think you can as it seems to get bigger each week and occupies valuable floor space. If you can make it small enough to be stored under another bench do it.
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