Fab Week

I was off work last week, so I tried to get as much welding done as possible. I had the sides and ends of the table’s base done, so all I had to do was cut some mitered gussets, prep the joints, clamp everything together and start tacking… How hard could it be?

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Sides, ends, and spans ready to be fit up.

First of all, there are a LOT of joints that needed prepped. I spent the better part of one afternoon just getting all the bevels ground and removing the oily coating that comes on the tubing from the areas to be welded. I could see how if you were doing this sort of thing all the time, it’d actually be worth it to get another angle grinder so you wouldn’t have to spend so much time switching back and forth between the grinding wheel and the wire cup brush. It’s only a minute each time, but it adds up and gets tedious.

My initial thought was to try to get everything squared up and clamped together before I did any tacks.  I used the long pipe clamps to hold the ends on and tried to use C clamps with scrap tubing to hold the rest of the joints square. As square as I thought I’d made the side and end assemblies, I couldn’t get it all to match up at the same time. I felt like I was playing whack-a-mole with a rubber mallet. I’d get one end squared up and the other end would come undone. I even got some 90 degree clamps from Home Depot. They looked a little light duty, but I thought it was worth a shot. It wasn’t. One broke as soon as tried to clamp it on, and another stripped out its threads as I tried to tighten it up.  Happily, HD gave me my money back with zero hassle.

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Early attempt to get everything clamped together at once.

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This Jorgens 90 degree clamp from Home Depot might be useful if you’re building a balsa wood birdhouse.

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Pipe clamp in place trying to help square things up.

I wasted way too much time before I realized that I could square up one end, get it tacked together and do one corner at a time on the other end. This left all the warping and twisting to be corrected on the last joint. I got it pretty close, but I was about an inch out of square when measuring the whole table diagonally both directions. I used a ratchet strap from corner to corner to bring it back into square before securing the spans with pipe clamps and tacking those into place.

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Ratchet strap holds everything square while pipe clamps hold the spans in place for tack welding.

Then it was time to start making some gussets. The saw’s manual recommends cutting square tubing tilted up on one edge so the blade’s going through a minimal amount of material. I realized that it wasn’t possible to get the cut I needed without laying the material flat in the miter clamp. I’m sure this reduced the life of my blade, but there was no way around it. I just took it slow when cutting through the flats.

Another issue I had when cutting the gussets was that they were too short for the clamp. That is to say that the short side of the gusset wasn’t long enough to extend beyond the pivot of the clamp. I wish I could say I was smart enough to see this coming, but I did end up shooting a gusset across the room before I wised up and added another clamp.

Also, don’t assume that just because the last number on the scale is 45 that if you rotate the clamp to its stop that you’re at 45 degrees. I made this mistake on my first cut and the piece didn’t fit right in the corner because it was more like a 50 degree cut.

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Cutting shorter mitered gussets requires supplemental clamping to prevent the possibility of projectiles.

And then more grinding and clamping…

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Gusset ready to be tacked.

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Measure, Measure, Cut, Grind, Grind, Clamp, Repeat.

Once all 8 gussets were tacked into place I moved on to the surface. While not part of my original drawings, I decided to put some braces made of scrap 3/16″ x 2″ x 2″ angle on diagonals across the surface. This should help support the water table since I reduced the number of ribs on the frame from 3 to 2. I decided to do that after looking at some other similar sized tables that only had 1 rib and deciding 3 was overkill. The angle braces will also help keep the frame square. I left the ratchet strap in place till after I tacked them in place.

When cutting the first one, I cut the angle iron to length and then laid it in place on the table and marked the apparent angle of the cut.  This turned out not to be nearly accurate enough, so I had to resort to trigonometry despite it being after 10 pm. I figured out what angle I needed and used my trusty metal protractor to mark the angle.

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High school trig saves the day.

Once I had cut the correct angles, I realized my usual clamping strategy wasn’t going to work to hold this in place.  There may be a more elegant solution, but this is what I came up with after some head scratching.

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Had to get a little creative clamping the angle braces.

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Must have been a productive day with all that saw dust!

The next day I cut the other two angle braces and tacked them into place. On both of them, I had one tack that looked as if it had no shielding gas at all. It’s taken me a while to figure this out, but that day was sunny and I had the big hangar door open. I’m thinking a breeze came through and blew away the gas?

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It was as if there was no gas, but the valve was open.

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Tacking on the second angle brace.

Before I tacked the third angle brace into position, I checked the squareness again. It took me way too long to figure out to use a welding magnet to hold the tape measure in place when checking the diagonals.

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Functional fixedness would be a detriment to progress while working alone.

After it was tacked in, I finally removed the ratchet strap and checked squareness again. It was within 1/16″.

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Look Ma! No clamps!

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I’d really hoped to be further along than this after my week off, but I’m happy to be taking my time and making sure everything is done as well as I know how (which may not be saying much…).  I got a little bit of the actual welding done, but there’s still a lot to do. I’ve gotten some good hints on out of position welding after my last post. I’ll let you know how that goes.

Also, all the electronics have arrived and I have Ubuntu and LinuxCNC installed on the PC I’ll be using, so expect some progress there over the next couple weeks. Don’t forget you can enter your email in the box to the right to get updates as they happen. Thanks for reading!

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