Almost done designing my table... - Router Forums
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post #1 of 12 (permalink) Old 03-16-2009, 09:49 AM Thread Starter
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Default Almost done designing my table...

Okay, so it's time for a dedicated routing station. I'm designing my own, but basically it's my version of Norm's table. There's enough pictures floating around out there I've been able to come up with my own design.

First of all, I'm raising it about 6" for my back (I'm tall) which gives more drawer space.

My question is about the top. Most people seem to be laminating two sheets of 3/4 stock and then covering with hardboard or laminate, etc. My concern is sagging over time, esp if I ever get a big heavy router (just a little 1 3/4 PC for now).

I'm tempted to build a torsion box, with a large space in the middle for the router. There's two reasons really, one is that the 2" webbing will directly support the router plate, and the other is that I want to build a torsion box for my assembly table, and I thought a smaller box would give me good practice before I take on a big 4'x6' bench. Plus I get a more rigid top that should reduce warping over time.

So I'm thinking 1/2 MDF for the skins and 2" strips of 3/4 ply for the webbing. Then a 3/4 melamine covered particleboard/plywood sheet for the actual top with T-tracks, etc.

My other thought, is I think I want to screw the top layer onto the torsion box, that way I can replace the top surface over time as it gets beat up. It's not as pretty with countersunk bolts on top, but if I'm going to put a good bit of time into the top, why not incorporate the ability to maintain it over time. That also gives me the ability to modify the top if I get a different router plate/lift over time. For now, I'm making my own out of 3/8 polycarb, it's easiest on the wallet seeing as how I'm about to buy a cabinet saw. It's served me well in the past. No money for a fancy lift at this point.

I'm almost done with the sketchup model, I'll post pics when I get there.

Whaddya think?
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post #2 of 12 (permalink) Old 03-16-2009, 11:20 AM
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The picture I've created in my mind from your description seems a little on the over-kill side - 3 3/4" thick, if I'm understanding you correctly. Depending on the spacing of the internal webbing, also pretty heavy, I'd think.

Conceptually, I do like the idea of using a torsion box, though.

- Ralph
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post #3 of 12 (permalink) Old 03-16-2009, 12:03 PM Thread Starter
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It's thick and probably heavy, but I'm not carrying it around on my should either.

My main concern is flat. I don't want to spend a good bit of time and money on this thing only to have it sag in a couple of years. I was hoping to hear from some people with the 2xMDF rout and how that holds up.

My other option is to make the top skin 3/4 ply, cut my channels in that, and use a hardboard top. That would cut down on the thickness a bit.
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post #4 of 12 (permalink) Old 03-16-2009, 07:14 PM
 
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I built my router table around the middle of 2004. Sold my house and gave it to a friend. I recently got it back from him about 3 months ago since he said he wasn't using it. I had built the fence out of oak 1x4's 6 layers deep - twist warped, the main base was out of 3/4 mdf and since it was left on a porch or back deck and got wet.... it too was in bad shape. The large paddle on/off switch had been a great home to some dirt dobbers. BUT the top that I made of out 1/2mdf and 3/4mdf covered on boths side with lam. and edges covered in 3/4 think oak... is still flat and I junked the rest of the old table and just recently built a whole new base and fence system. I had glued the two together and used 1" sheet rock screws counter sunk down thru the 1/2 mdf into the 3/4 mdf. The top is 24"deep and 36" wide. And since the middle section where the router is, is only 12" wide then there are two drawer sections on each side - base is 19" deep and 24" wide - the top has had plenty of support.
So for me.... doing a mdf to mdf layer for a top is the way to go...but that is just me and what I have experienced...first hand.

Here to help anyway that I can...
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post #5 of 12 (permalink) Old 03-17-2009, 11:45 AM
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R, as I understand things, the torsion box gains its strength more from the internal lattice as opposed to the skin. Thus, you could probably get by with 1/2" thick stock for the internal lattice, and 1/4" thick material (Baltic Birch ply, perhaps?) for the basic skin. Then, laminate a layer of thicker material on the top to accommodate the T-tracks, etc. I'm also not sure the internal lattice pieces need to be 2" wide. Probably 1" or so might be sufficient. That would give you 1 1/2" thick for the basic torsion box, plus 3/4" for the top layer.

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post #6 of 12 (permalink) Old 03-17-2009, 12:10 PM Thread Starter
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Quote:
Originally Posted by Ralph Barker View Post
R, as I understand things, the torsion box gains its strength more from the internal lattice as opposed to the skin. Thus, you could probably get by with 1/2" thick stock for the internal lattice, and 1/4" thick material (Baltic Birch ply, perhaps?) for the basic skin. Then, laminate a layer of thicker material on the top to accommodate the T-tracks, etc. I'm also not sure the internal lattice pieces need to be 2" wide. Probably 1" or so might be sufficient. That would give you 1 1/2" thick for the basic torsion box, plus 3/4" for the top layer.
You read my mind. I picked up an old WW magazine from a few years ago and they discussed torsion boxes. The author made a box out of 1/4 skins and 1/2 ply core. He made it 24" long and they have a picture of him standing on it. I'm a little weary of 1/4 skins, but I have some ply left over from my last project, I can build a box entirely out of scrap and give it a whirl. I hate working with MDF anyways.

I'll see if 1" is too small to handle... the trick is ripping that ply without a ton of tearout, I got the cheap stuff and laminated the 1/4 on top of it for my last project.
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post #7 of 12 (permalink) Old 03-17-2009, 06:51 PM
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Hi Rob and others:

A while ago, I did a design for a torsion box. In the process, I used an Excel spreadsheet to do the calculations. I am posting this Excel spreadsheet so that it can be of use to anyone who would like to use it. The spreadsheet is in Excel 2000 - 2003 format and contains no macros.

Since the forum appears not to like XLS files, I have put it in a ZIP file.

Cassandra

Last edited by Cassandra; 03-23-2009 at 09:03 PM.
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post #8 of 12 (permalink) Old 03-21-2009, 11:23 PM
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Oops! Mea Culpa!

I found an error in the Excel spreadsheet.

Sorry about that!

The error results in calculating a greater deflection value. I have corrected the formula and reposted the torsionbox.zip file. Please do not use the one in my previous email.

The spreadsheet is based on the Torsion Box chapter from Ken Horner's book, "MORE Woodworkers' Essential Facts, Formulas & Short-Cuts"

Thanks,
Cassandra
Attached Files
File Type: zip torsionbox.zip (7.7 KB, 53 views)

Last edited by Cassandra; 03-21-2009 at 11:28 PM.
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post #9 of 12 (permalink) Old 03-22-2009, 07:56 AM
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I build my top with two MDF pieces glued together. For the average size of a router table I will never think about sagging no matter what kind of a router I will use.

Its a different story if the top is going to be 4 ft or longer

Nicolas
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post #10 of 12 (permalink) Old 03-22-2009, 11:21 AM
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Rob, 3/4" Baltic Birch plywood covered top and bottom with high pressure laminate is ideal. This will not sag, the laminate keeps out moisture, wood slides on it easily, is easy to clean and can be marked with pencil for reference points. This is how the Router Workshop table is constructed.

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