Walnut Slab Coffee Table #1: Flattening slab with router sled

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Blog entry by Lumber2Sawdust posted 01-01-2012 07:14 PM 20138 reads 9 times favorited 5 comments Add to Favorites Watch
no previous part Part 1 of Walnut Slab Coffee Table series Part 2: Finishing and the final result »

I started a post about a wood gloat about a month ago. I found some nice walnut slabs at a sawmill for some projects. The first one up is a coffee table. I thought I would start a blog about the process of preparing the slab. I may follow this with more about adding a base to the table as it progresses.

I’ve done a fair number of projects in the past, but nothing involving a big slab like this. I have been excited about getting this project started, but Christmas was approaching fast and I had to finish some gifts to send to the east coast before it was too late. In the end, it was too late when I sent them, so they didn’t arrive until after Christmas. Luckily, the recipients are forgiving, and really loved the lamps that I made.

Now that I had shop time for my own purposes, I was able to get started on the coffee table. The first thing I had to do was build a jig for the router to flatten the faces. I created a sled like the one described in Fine Woodworking (issue 222, I think). It is basically a bridge over the work piece which allows the router to ride across a level plane above the piece. It took me a couple of nights in the shop after work assembling and flattening everything I needed to get the jig set up.

When the jig was ready, it was time to rearrange my shop. I had to wheel the table saw out of the middle, and drag my bench out so that I had access all around it. It didn’t take long to shim the legs of the bench to get it all level. Leveling the bench is important because you will use the level on top of your work piece to determine the plane to which you want to flatten the slab. For the slab I was working on, it had a twist from one corner to the other, and it was thicker on one end. I was pleasantly surprised at how quickly I was able to get it shimmed to where I was happy with it. I have to admit, it is a bit stressful, at least the first time doing this, because you really just take a good guess about what it the best position. If you proceed cautiously, you can adjust as you make progress. I had to make a small change. More on that later.

Here is the initial setup on the workbench:

You can see the stretchers that the slab is sitting on. These will hold the rails for the jig. There are about a half dozen shims and a strip of 1/2” ply between the slab and the stretchers to get it leveled the way I wanted it.

I built my jig around my new Triton router. I’ve heard a lot of good things about the Tritons, and a few bad things as well. In short, I can say it is far and away better than the dewalt 621 that I’ve had for a long time. The Dewalt is dying a slow death, so I went with the Triton. As a bonus, it comes with an “extended base plate”. That meant that I didn’t have to buy a router table plate. The router is on its base plate and the trough is just big enough to allow the router/plate to slide across it.

With the jig all set up it was time to start up the router and see how this thing works:

Basically, I needed to find the highest spots and start lowering them. The first couple of passes were pretty quick because there were a few high spots that came down quickly. I lowered the router some more, and adjusted the jig down, too, to work more of the slab.

I was really excited with how fast and easily this operation was progressing. I got a little farther than in the last photo and decided it was time to assess how the slab was looking, more closely. In doing so I realized that the low spot on the left if the previous photo was about 3/8” lower than the spot across from it on the other edge of the slab. I didn’t want to have to remove that much wood to get it down to that level, and I wanted to keep the slab as thick as possible. That meant it was time to re-level it. I lifted up the left edge with some shims, and used the lower edge of the router sled to determine when the low spots on each side were in the same plane. This was only a 10 minute operation to get it adjusted. Then it was back to making more sawdust.

By the way, leveling a slab this way is a good thing to do when your shop is really dirty and in need of a good cleaning. You are going to get wood chips EVERYWHERE! I filled 2 garbage cans with chips, and I’m not close to done.

Back to flattening, this is where I had to stop for the night:

It was shaping up very nicely. You can see the track marks that the router leaves striping their way across the slab. They are very shallow and will come out easily when the time comes. I still had a few low spots, but this was very close to being done. It took me about 2 1/2 hours to get this far.

The next day, I couldn’t wait to get back to the shop and continue this project. Now that the top was basically flat, flipping it over to level the bottom becomes easy. I stood the slab on edge, removed all of the shims, and laid it top side down. It didn’t wobble at all.

At this point, it started to go faster. I was confident that the top side was flat, and I was happy with the way it looked. Now it was just about making the bottom side parallel to the top side. I reset the router and sled to hit the high spots and started working again.

After 2 or 3 passes the highest spot started coming down:

In another 20 minutes, I was getting pretty close to done:

I was amazed at the incredible figure in this slab. It seemed every time I flattened out more of it, the figure just kept getting better.

I took a break for a while to ponder how much I wanted to work the bottom and the top, then came back to finish up the routing. The bottom isn’t totally flat, but the low spots are in places that will still allow a base to support it well. I went back to the top side and finished leveling it out a little better.

The router left some tearout in a few places. I think that is because I was taking a fairly wide (but shallow) cut. The angle of the cut near the edge was not supported, causing the tearout. I guess that will be a test for my finishing skills.

Overall, if you want to work with a slab like this, the jig and router method is well worth it. I bought a 3/4” sheet of birch ply, 2 straight 2×4s and a 10’ 2×6 from the BORG for this project. That totalled about $60, and I have half a sheet of ply left for other jigs. I think it was about 4 hours total to get the slab flattened. It was my first time, and I was being cautious, and enjoying the process so it took longer than it needed to. I enjoy using hand tools for most things but I would have never attempted this project with a couple of hand planes and winding sticks!

I plan to add another entry about finishing the rest of this project. I am hoping go make progress on it soon, so I have something to add here. I need to get to Woodcraft to get some epoxy to fill the knots/splits in the slab. The store is about 10 minutes from where I work, but about 50 minutes from my home. I’m not going to make a special trip out there this weekend to get it, although I would love to make some more progress in it this weekend!

5 comments so far

View deleteme's profile


141 posts in 2688 days

#1 posted 01-02-2012 02:05 AM

Thanks for sharing. I’m hoping to use this method for planing large slabs as other traditional power tools are quite expensive. I’m sure that you must have had knots in your stomach most of the process (The fear of ruining fine wood both worries and excites me each and every time). I’ll be tuning in for this series. Have an amazing New Years.

View CalgaryGeoff's profile


937 posts in 2564 days

#2 posted 05-09-2012 08:07 AM

Very spectacular build and massive board you milled up. Most effective job.

-- If you believe you can or can not do a thing, you are correct.

View woodman44's profile


43 posts in 2772 days

#3 posted 03-01-2013 07:52 PM

Hi Lumber2sawdust,

I am planning to make a similar coffee table from a slab for the top. I could not find any other posting from you regarding how you finished the table, specifically how you designed and attached the legs to the slab.

Could you share how you completed the project and the leg construction?


-- Ken, Michigan

View frankmoney77's profile


14 posts in 2107 days

#4 posted 05-09-2013 07:32 AM

Hi Lumber, I’d have to agree, i’d love to see how you went about the legs as well. I just picked up a 4’ round of maple to make a few tables out of. But most of all I’d love to see some details on how you built your jig. the round being 4’ wide i won’t be able to go to my buddy’s mill, his has a max of 28” it looks like a chain saw as careful as i can, and then i need to construct the same type of jig you used here to smooth the face. any photo’s?

-- Master Craftsman of novice things

View Lumber2Sawdust's profile


139 posts in 2947 days

#5 posted 05-09-2013 02:07 PM

Hey Frank,

The jig I made came from Fine Woodworking #222. You can the plans from there and will be way better than I could repeat here. I added a second blog post in this series which shows what I did for the base. I ended up not using wood on the base because my wife really wanted a metal base.

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