How to get a table flat

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Forum topic by Fuzzybearz posted 08-08-2018 02:57 AM 950 views 0 times favorited 18 replies Add to Favorites Watch
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104 posts in 673 days

08-08-2018 02:57 AM

I am trying to build my own 4×3 router table by gluing together plywood and mdf. I totally shouldve bought a cheap tabletop and created a hole, but im too deep into this project for that.

Anyways, the corners of my router table are flush with the wood, the middle parts are depressed (the table not the router table). Whats the fix now? Do i put on some hardening putty then glue another layer of 1/4 plywood then shim the router table up?

Bench dog cast iron table about 17×11. The wood tabletop is 4×3. Core MDF with 2 layers of 1/2”plywood sandwiched again by 2 layers of 1/4” plywood. Going to add formica top when im done.

18 replies so far

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104 posts in 673 days

#1 posted 08-08-2018 02:57 AM

Excuse the cuts. I used a spiral cutting router blade. Rockler guy would work Im going to buy a trim.bit.

View Aj2's profile


2649 posts in 2402 days

#2 posted 08-08-2018 04:00 AM

It’s it just sagging?, plywood is kinda stiff but mdf is heavy. Did you glue it all together on a truly flat surface.
The fix could be to put a leg under to push it up?

-- Aj

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104 posts in 673 days

#3 posted 08-08-2018 05:51 AM

Nope. Ididnt think to glue it on a flat surface : / i dont think the wood itself can be propped up.

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5136 posts in 1193 days

#4 posted 08-08-2018 09:16 AM

You can feel good about at least one thing. You bought a great router table top. The Bench Dog is rock solid and dead flat. Once you get the rest figured out you’re going to have one awesome router table.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View clin's profile


1076 posts in 1600 days

#5 posted 08-08-2018 10:26 AM

If your tabletop sandwich wasn’t flat when you glued it, it would take a lot of force to pull it flat. Only way to do that would be stiff, straight framing underneath.

I don’t think it is worth the effort. I’d rebuild the top and would look at making the top a torsion box using 1/2 MDF. If you could make the top 3” thick without interfering with the function of the router, you would have the top and bottom sheets of 1/2” MDF and internal 2” webs to give you 3”.

In case you are unfamiliar, a torsion box allows you to build a top that is almost as stiff as the equivalent solid top would be, but at much less weight. The reason I suggest MDF is it tends to be very flat. It is also inexpensive. It is heavy, but again in a torsion box design using 1/2” it shouldn’t be heavier than what you have now.

I’d also laminate the top with Formica or similar for wear resistance.

A torsion box isn’t magic so you still must build it on a flat surface. Perhaps you could use your table saw if you have one large enough.

-- Clin

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1496 posts in 3454 days

#6 posted 08-08-2018 11:14 AM

Sucks to say it but I think you’re at a point where materials and time do not warrant trying to fix a poor top. Take the first one as cheap education and you’ll find the second build will go much smoother, quicker & better. Look for a plywood/sheet goods supplier in your area. There is a Ultra-Light MDF that you can’t get at the box stores which is a great product. Try the places that say they’re wholesale only and see if they do “contractor-sales” on site, I’ve found a place near me where I can get the stuff without order minimums, just walk in ask for three sheets & they bring it out on a forklift and help me load. In my area 1/2” ultralight is $30 a sheet

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

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326 posts in 1135 days

#7 posted 08-08-2018 01:12 PM

I too think you need to call that top a loss and try again. Get a flat surface to glue up on. Do a youtube search on winding sticks. Watching someone use them clicks a lot faster than reading about them in my opinion. I believe WoodWhisperer did a video on building a torsion box. No need to make a whole torsion box,but that setup for making a temporary flat surface to make another flat surface is what I would do. Unless of course you have a big enough flat surface already.

View Fuzzybearz's profile


104 posts in 673 days

#8 posted 08-09-2018 12:03 AM

You know. I flipped it over and it is mostly flat.

I think i knpw what happened, the part where the router table is inlaid, I had cut apart and then reglued back in around the bench dog. I didnt want to use my router, dumb mistake on my part.

So when i clamped it, whatever little gaps between all the pieces moved a bit and bent. This is how the underside is still flat.

Im going to buy one last piece of wood and see how it works : ) thanks guys

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104 posts in 673 days

#9 posted 08-09-2018 01:31 AM

I lied. That piece is certainly curved. Guess ill call it a loss and start anew

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104 posts in 673 days

#10 posted 08-09-2018 01:32 AM

I have a flat surface but the clamps throw it off? How do i stop the clamps from getting in the way?

View Rayne's profile


1298 posts in 2144 days

#11 posted 08-09-2018 01:54 AM

Do you have enough surface area to mount the extend surrounding to your base? Maybe it’s just me, but I’ve never seen a router table build using a router table and making it bigger to put on a custom base. It’s always been just the inserts from the builds I’ve seen thus far. Anyways, If you have a flat base, I’d use 3/4” MDF for 1 layer and Melamine for the Top layer. Those two together will be heavy and super flat. I didn’t use any glue to put them together; just a LOT of appropriate screws and then screwed the top to my base to keep it there and flat.

View Kirk650's profile


679 posts in 1353 days

#12 posted 08-09-2018 03:02 AM

Do what clin suggested. That worked great for me. Except that I didn’t top it with Formica. I put on about 3coats of water based poly. Years pass, but still looking good.

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1076 posts in 1600 days

#13 posted 08-09-2018 03:31 AM

Do what clin suggested. That worked great for me. Except that I didn’t top it with Formica. I put on about 3coats of water based poly. Years pass, but still looking good.

- Kirk650

Just a quick comment about plastic laminate. I was concerned the first time I did it. It turned out to be boarder line trivial to do. Probably less overall effort than applying multiple coats of a finish. Nice thing about it is it is very durable and slick so is a great surface for anything you slide wood over.

I wish I had used it on my out feed table instead of the melamine. The melamine works great, but is showing a lot of wear.

-- Clin

View MrRon's profile


5810 posts in 3848 days

#14 posted 08-09-2018 05:33 PM

I would go with MDO (medium density overlay). This is a plywood that is used for outdoor signs. It has a resin impregnated surface that resists warping.

View Andybb's profile


2353 posts in 1208 days

#15 posted 08-09-2018 06:36 PM

Start over with something flat using your choice of any of the suggestions above. Also check that corner radius. The metal top looks like it would fit better with a 1” wide trim bit vs 3/4”. Cut a test corner as you may need to make a template. Shame on the Rockler dude telling you to use a spiral bit.

I also used 4 coats of Varathane wb poly instead of any laminate. It’s made for wooden stairs and is bullet proof and sold at Home Depot.

-- Andy - Seattle USA

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