After a number of fits and starts, I have most of my 80/20 system together. As much of it is the same (extrusions and such) as everyone else has done, I'll just concentrate on what I did differently and why I use the word system to describe it.
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The basics are I used 40 series extrusions and carrymaster casters. On the main table I have a full shelf underneath the top to allow access to the underside of the top and to keep items I'm using at the time. For the shelves below, I chose to keep them open with the drawer glides attached directly to the extrusions. They become structural members as if the worktable needed to be any more stable. Eventually, I'll probably make drawers to go in the center section.
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This image shows the connectors I used. The m4 screws and drop in T nuts are to mount the drawer slides. I mainly used the end fasteners on the right wherever a fixed connection was needed. I used the anchor fasteners on the left when a piece of extrusion might need to be moved or added temporarily (you'll see what I mean in a few minutes). I used the panel brackets to support the top. This is the main feature I hadn't seen anyone else describe using.
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Here is a more open look at the second unit I built which has the same long length as the first but is only half as wide. You can see how the panel brackets are attached.
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To get the top to sit up from the extrusions, I built a frame from 3/4 ply and used loose dominoes as connectors.
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Then I cut the top to the exact dimensions of the extrusion arms, drop it in and tighten the connectors. I might later directly attach the top but so far it hasn't been necessary.
The rest of this is talking about how I finally made the tops.
It started from the excellent post by Michael_Swe
http://festoolownersgroup.com/festool-jigs-tool-enhancements/make-a-perfect-%27mft%27-with-qwas-raildogs/msg238735/#msg238735
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The first change I made was to make the first set of holes in jig boards instead of on the blank itself. I actually drilled both boards at the same time and flipped one.
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One other difference from what others have done is that I wanted the first row and column to be exactly 28 mm from the edge (more on that later). I'll also show what the 32mm offset shelf pin holes are for.
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In this step and most others in making the top I don't think I can possibly overstate the importance the Incra precision T-rule has been to me. It has become a go-to tool.
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Here is my setup for drilling the top. Keeping the jig precisely aligned was critical so I used three bar clamps so I could always have at least two attached at all times.
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Probably the most controversial (heretical?) thing I did was to precisely drill a hole in the rail to fit the pin hole in the jig to get that 28 mm distance from the side. I used this as a coarse adjustment that I refined later.
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I also couldn't overhang the side guide holes to use the Qwas rail dogs and keep everything stable while drilling. So I used these threaded sleeves I got from John at tool improvements. They let me work on a flat tabletop. I don't know of anyone currently making these but as they make excellent rail pups I would expect that any of the current dog suppliers could make a set.
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For the drilling operation I used three bits. The first is a Whiteside 25/32, second the Festool 20 mm, and finally a pin I had on hand which is part of the Micro Fence circle jig. This made for a lot of bit change out during the process but as they each used a different collet, the process went fairly smoothly. At the start of each row I used the centering pin to make a fine adjustment then clamped the rail and removed the shelf pin from the rail. I used the Whiteside bit which was slightly undersized to remove most of the material. I found best results at not drilling completely through with this bit even using a backer board. I have a bias toward using a 1/2 inch shank when drilling through thick material. I then used the 20 mm to size the holes and make a clean exit through the board.
Then wash, rinse and repeat and you have a board full of holes.
Now I have two tables, one with a holy top and one without. Here comes the system part.
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By simply using two more pieces of extrusion and a second drilled top flipped with respect to the other, I now have a top that is a little over 4 by 8 feet.
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Looking down the line you can see what I was hoping for.
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First, it passed the square test.
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Second the other thing I was trying for worked as well. If you had been doing the math you would have seen that 28 mm times two plus a 40 mm extrusion gives a 96 mm hole space between tops. The only thing I had to demonstrate this was this part from my MFT 1080s.
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Now it is time to get to work. But as you can see, the next top I build will be much easier.
Sorry this was so long but I hope you found the read worthwhile.
Dick Perry