Monday, October 30, 2017

My Sandbox

Morgan Demers' molding bench got me thinking about what a good idea it was to have your molding bench near your pouring area. For one thing, a flask full of sand is heavy. He also put his sandbox on casters, so it would be easy to roll from the molding bench to the pouring area. That should also reduce the chances of jarring the flask and causing the sand to shake loose in part of the mold or collapse entirely. I was sketching out various ideas when the thought occurred that the greatest chance of such a mishap was in lowering the flask from the bench to the sandbox.

What if you put them at the same height? As Uncle Dave pointed out, you could do all your molding on the ground, but a molding bench would raise the work to a convenient height. You could raise the sandbox to the same height as the molding bench. But isn't the molding bench itself basically a box full of sand? Could you pour over it? I don't see why not, and once the pattern was drawn and the flask reassembled, you wouldn't have to move it at all.

But that would require lifting the crucible out of the furnace, raising it above the bench, above the flask, and then pouring. All that extra movement of a glowing flask filled with molten metal sounded like an unnecessary risk. So eliminate it. Expand the benchtop / sandbox to make room for the furnace. It needs a bed of sand 2" thick, and maybe some firebricks to rest on and to set the lid on. But won't it be awkward and dangerous to lift the crucible to shoulder height or above? Will you even be able to see the sprue as you pour? If the mountain won't come to Muhammad...

Build some steps near the furnace. Stand at ground level to prepare the mold, then climb the steps to melt and pour. Ideas were coming thick and fast now. I revised my plan through many drawings, and made further changes during construction.

With all that weight on it, the bench needs a broader base. I had some concrete blocks left from another project. I'm no mason, and since I rent, I may have to tear this down and move it at some point, so I stacked the blocks dry. I wanted the most stable arrangement I could get. I thought of a running bond, but I had no way to break blocks, I didn't want to pay extra for special blocks, and I wanted the 4' x 4' base to come out even. I settled on a basketweave pattern, alternating directions with each layer.

Something I learned when I worked in the shipping department at Rust-Oleum: when stacking rectangles of identical size, the stack will be more stable if they don't line up exactly. Because the layers alternate directions, each block rests on two blocks. Because the layers don't quite line up, each block also rests partly on a third block.

The base is 48" x 48" x 24" with 8" steps.

I used salvaged wood (mostly laminated particle board) for the bottom of the sandbox.
Some good quality dimensional lumber turned up on the curb just in time for the sides. I used 2x6s for the molding area. Since the furnace area only needs 2" of sand, I used 2x4s there.

As usual, spring clamps and electrical junction boxes held things square for assembly.

I vaguely remembered reading that concrete could wick moisture up from the ground, and that wood structures on a concrete foundation needed a water break to keep the wood from rotting. I had several blue tarps from Harbor Frieght's free with any purchase coupons, so I used one under the box, one to line the box, and one to shed rain.

I made a lid to keep out cats and weather.

Weights, bungees, and tent stakes hold a tarp over the lid to shed water.

Sunday, September 24, 2017

The Workbench, Part 6

I forgot to put particle board on the back side of the bench when it was accessible. When I put something in the vise and gave it a good shove to the left, the bench racked to that side. Since it was now too heavy to roll, I had to crawl under the bench and reinforce it from the inside. It would have been much easier to do from the outside when I had the chance, but now the bench is rigid.

Dave recommends making the drawers shallow enough to arrange the contents in a single layer. If you have to dig through your drawers, you are doing it wrong. I started with a drawer for layout tools. For a drawer this shallow, lath was just the right dimensions. I used salvaged hardboard panelling for the bottom. I followed the directions at Build Basic. Because the drawer was shallow and the lath was thin, I glued everything together without hardware, so I didn't need pocket holes. I used 4" Square Electrical Junction Boxes and 1" Metal Spring Clamps to clamp the corners square for gluing. Checking with a machinist's square, I found the boxes remarkably accurate. Be sure to check each one, though. I did find a few that were a little off.

The problem with designing storage to exactly fit your tools is that they often only fit one way. If you remove tools and open and close the drawer a few times, the contents can slide, roll, or shuffle enough that you can't put your tools back in without tidying the drawer. To prevent this, first I traced around each tool with a Sharpie, so I'd know where everything fit.

Then I cut dividers from Bamboo Skewers and glued them alongside each tool.
Next, I set out to organize my screwdrivers so the proper one for a given job would be right at hand. I realized I had several partial sets, and other screwdrivers acquired piecemeal over the years. I decided to start over with a complete set of all the sizes and types I was likely to need. I found what I was looking for at Harbor Freight.

I built a handy storage rack from scrap particle board. It took me longer to build than I care to admit, but I didn't take shop in high school, and it does the job.

I read about a rasp plane, and thought it might be the right tool for leveling / smoothing my bench top.

It has many fine teeth that each make a shaving between the size of sawdust and the shavings of a conventional plane. It doesn't catch on edges and irregularities like a conventional plane, and it appears that if one tooth is dull or damaged, the others cut just fine. When the teeth wear out, the entire set is replaced rather than sharpened. So far, it seems to be working better than a conventional plane, but it is still slow going. I'll work on it in odd moments, and report the results. I'll add more drawers and other storage as needed. Now I'm ready to return to the furnace and foundry.

The Workbench, Part 5

This was my only vise.
Looking back at Book 2, The Metal Lathe, I saw that the lathe was fixed to the bench by four bolts, which could also be used for  leveling. I realized that I didn't need a smooth bench top under the lathe, or even a level top, just a rigid one. I tried bolting my vise to the bench, and it worked just fine. I added a second vise and a bench grinder.
Now I have two.

When I added boards to the top, I lined them up against the wall. I figured this would keep the front and back edges relatively straight, and minimize the chances for things to fall behind the bench. I forgot that:

1. I had meant to have a 3 inch overhang in the front for clamping. Because there was a double layer of baseboard, (I have no idea why) my overhang was now in back.

2. I had meant to screw particle board to the back of the bench and extending a few inches above the top to make it rigid and serve as a backstop. There was no way I was going to roll it over now.

3. With the bench top against the wall, all vibrations would be transmitted to a partition we share with the neighbors. (I live in a duplex.)

Using a crowbar, I was able to move the bench about a half inch from the wall. That should reduce vibrations in the wall, but now I had a gap behind the bench, and nothing to keep small parts from rolling off. I laid a 2x4 along the back, but with such an uneven surface, I worried that some parts might be small enough to roll under the 2x4. I cut a groove with a circular saw, stood 1/4 x 2" lath in the groove, stood the 2x4 on edge behind it, and laid 1x2s flat behind that. I screwed the 1x2s to the bench, screwed the 2x4 to the 1x2s, and glued the lath to the 2x4. A complicated solution to a problem that could have been easily avoided.
The clamps are holding the lath in place while the glue dries.

I attached power strips to the 2x4, hung a shelf from the joists above the bench, and clamped reflector lamps ($6.47 each at Walmart) to the shelf.

It may look like I am overloading the circuit, but the power strips are rated for a full 15 A, I put LED bulbs in the lamps, so they only consume 15 watts each, and I only use one power tool at a time. The power strips are to save plugging and unplugging.

Monday, September 18, 2017

The Workbench, Part 4

Two views of the bench top:

The top boards were screwed to each other, but only attached to the rails at the ends, so the top could flex upward anywhere in the middle. Not good. I screwed it to the rails at intervals along the length with the longest screws I could find.

I was saving for a car, but I splurged and bought a plane.
I had planned to level flatten and level the bench top with a hand-held 3x21" belt sander. I bought the coursest belts I could find, 36 grit. The belts ripped almost immediately. I tried planing the surface. It took a little practice, but I learned to make those famous long, curly shavings. This was going to take a long time, and because the top was so uneven, it tended to nick the blade every time I passed over a low board and then hit a higher one. I had to keep taking the blade out and sharpening it.

Sunday, September 10, 2017

The Workbench, Part 3

Building the bench top was a long, tedious process. First, because the pallet boards were anything but straight, I had to test-fit each board against the preceding board in four possible orientations to find the best fit. Then I drilled pilot holes for the screws. Because the whole point of this massive top was to have a rigid base for mounting the lathe and other machine tools and the boards were 1.25" thick, I used 2.5" screws. This meant I had to stagger the screw locations to prevent the point one screw from running into the head of another.

I used two drills, one to drill the holes, and the other to drive the screws with a driver bit. In the foreground is a "sled" a movable work surface to set tools and materials on. It's a scrap of particle board with short lengths of 2x4 screwed to the underside on each end to keep it from sliding off the boards it rests on. It was especially helpful in the early stages of the process, when I hadn't built enough of the top to set anything on.
I had meant to take more pictures of this process, but it was so mind-numbingly boring, that I forgot. I wore out my drill bit early on. I had extra bits in a few common sizes, but not the right size for these screws. I thought I'd just buy a multi-pack of that size, which was how I'd acquired the spares I had, but nobody seemed to carry the size I needed, except in a complete set. I had actually bought a bench grinder and extra bits several months before, intending to practice sharpening them, but I couldn't master the physical skill. The bits always came out worse than when I started.

Monday, August 14, 2017

The Workbench, Part 2

The previous occupant divided our basement into mostly small, oddly-proportioned spaces. One space just off the laundry area is too narrow for most uses, so we use it for storage. I sorted through it, removed a lot of clutter, and consolidated the rest, freeing up a space 5 feet by 12 feet. I designed my workbench to fit this space.

First I constructed slide members, rectangular pieces that support the bench top and hold the drawer slides. I wanted them to be 30" x 33" but particle board wider than 18" is pretty rare in RTA furniture, so I built each member from an 18" piece and a 12" piece. The boards at the top and bottom are pallet boards 1.25" x 3.5".  I'll add the drawer slides later.

Since the back would go against the wall, I had to start with the front side down and attach the back rails first.
I hit on the idea of using concrete blocks both to square up the assembly and to space the slide members. That meant carrying 36 blocks down to the basement. Was I sore afterward! I haven't brought them back up the stairs yet. I wouldn't recommend this method, and I certainly wouldn't do it again. It worked, but the blocks are just too heavy.

Here is the bench with the back rails attached.
Then I had to roll the bench upright. I managed to do it alone, but it would have been much easier with a strong helper.
Then I squared up each slide member and screwed it to the lower front rail. That held it square while I attached the upper front rail.

Somehow, three of the slide members ended up too tall. I sanded two of them down, but the third was much taller. I tried cutting it down with my circular saw, but that didn't work very well.The best tool for the job turned out to be a wood chisel.

Here is the wood for the bench top. South Bend recommends that a bench top lathe be bolted to a wood bench with a top at least 2" thick. I'm using pallet boards on edge. Even after sanding it level the top will be about 3" thick. I think that's about as rigid as I can get with a wooden bench. I started the top Sunday afternoon. I'll finish it next weekend.