Split Top Roubo Bench Build #18: Top flattening, parts 1 and 2

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Blog entry by ic3ss posted 04-13-2015 03:49 AM 3593 reads 0 times favorited 0 comments Add to Favorites Watch
« Part 17: Ok, I think I've recovered now Part 18 of Split Top Roubo Bench Build series Part 19: Done! »

I didn’t write the final post last week as I was pretty busy with my 20th wedding anniversary. Last weekend I had planned on flattening the tops on my last day off but only got half of it done.

I had decided to use the router to flatten it, using a sled and rails. I saw the technique on the Wood Whisperer video and thought it was a good idea. So I went to the big box and got two 2×6 kiln dried 8’ long boards for the rails. The first thing it to make the edges straight and then rip the other edge to make it parallel.

I thought I needed to first flatten the bottom surface so I did each half in turn. The top is sitting on two narrow boards that are exactly the same height and straight. Of course my concrete floor has some dips and hills in it that aren’t apparent until you put a straight edge on it. The boards had to be shimmed and I went for level here so I could tell that they both sat parallel to each other. I have a high accuracy level that’s 0.05 mm/m. So when the two are set and shimmed for support, I lifted the front half and set it on the boards careful not to disturb the placement.

So then the rails go on the sides of the top and I put just light clamp pressure, just enough to hold them in place. I set the router to take the slightest shaving off of the lowest point, then repeated with the back half.

When the front half was done, I still needed to dig out the channel for the deadman to ride in. This was the perfect time for this before placing the tops back on.

With the tops off of the base, I also filed a bevel on the left short top rail between the tops, so the gap stop will ride up a little easier.

Another thing on the list was to seal up the end grain on the bottoms of the legs, so I flipped the base over and put as much poly as it would take. I was careful to only put it on the bottom and the bottom bevel, end grain only here. I think I’m going to put either BLO or danish oil on it, but that will be later. But I want the legs to be as sealed as I can make them on the bottom.

So with the tops back on the base I was running short on time, I had a dinner date. But just like me, I couldn’t just walk away. I set up the rails using the boards that had supported the tops on the garage floor. I clamped these boards cross ways at the ends and used the protruding ends to hold the rails, then clamped the rails. They were still straight and I got it all set up quickly, so I went to work with the router sled.

And then it happened. . . .

I was going too quickly and the bit walked out of the collet and did this. It cut almost 3/16” deep, way deeper than I had ever intended to cut. I think it was a number of things that caused it. Me going too fast, I never cleaned the oil from the shank of the bit, it’s a new bit, and I also hadn’t cleaned the collet or even checked if it needed to be cleaned. Oh well, it was a good time to stop and get cleaned up.

I’m proud of myself, I didn’t even sulk about it. I did my work week and just decided that the 3/4e top will be just a bit thinner than I had hoped. 4” was the magic number but it ended up at 3 3/4” instead. No biggie.

I had left the rails on all week, so when I went back to it today I checked them for straight, and they were not. Got them straightened out again and flattened the top, using my mistake from last week as my depth gauge. This time I cleaned the collet, cleaned the bit, and went slow and methodical and I got it done.

I’m so glad that this is over, I had been kind of sweating this part almost since I started this project. I have decided though that if I ever use this process again, I’m going to find some straight metal rails and use those. Dealing with wooden rails that never are able to stay as straight as they need to be is a real pain.

I sill had some time left in the day so I went ahead and cut the beveled rail for the deadman to ride on. This was how I bent my saw blade a couple of weeks ago, but this time I remembered to pull out the zero clearance insert before tilting the blade. So I got that done and screwed on the front rail, then cut pieces for the shelf supports and put them on.

I also put some time in easing all of the edges. That took some time and my back is sore now. Tomorrow I’ve got some honey-do’s and I hope I can get back to this, but there’s always the next day. I have to make the deadman and the shelf, and that’s it. I’ll be done. Woo-Hoo!

Have a great day and thanks for reading.


-- "I am endeavoring, ma'am, to construct a mnemonic memory circuit using stone knives and bear skins."

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