||[Oct. 11th, 2004|12:21 pm]
Saturday, as I wrote before, I went to the tool yard sale. Ended up selling a bunch of tools, made about $240 in the deal. I also managed to avoid buying any new tools, though I drooled on Thalx's vacuum pump.
There's another local tool frob this weekend, offering free tailgate sales. I might hit that one up as well, though it starts at an ungodly hour,
7am. We'll see.
I decided the wheel of the pizza cutter I've been working on just wasn't good enough, too many inclusions and delaminations, so I made another billet, this time taking photos of how it's done, or at least of how I do it. I'll put those up tonight, though sadly a bunch in the middle didn't survive -- batteries died before I could pull them off.
Basic process is still the same: take several pieces of steel, I used 5 (3 layers of L6 interspaced with 2 of O1), take off the oxides coating it, stack, clamp, wire, flux, and weld. The good news is that this only takes me about an hour to the first weld, whereas previously it was half a day to get to that stage. Practice, indeed, makes perfect. Or at least better than what was before.
After the first weld, always the hardest, I used the power hamer to flatten it out, and folded once and welded. Got some borax flux in my glove, essentially molten glass, which left (counts) 10 blisters on my hands, fortunately none very large. My bad, I left my welding gauntlets in the truck, and didn't think I needed to go get them for this work. I was wrong. At least now I'll have scars to remind me in the future.
Some people have asked what does the borax do? Well, it's one of the oldest forge-welding fluxes known, dating back about 3000 years. It occurs naturally, and performs two functions: it dissolves iron oxide and suspends it in a liquid state, and it keeps the surface of the metal from any oxygen. Since welding requires metal-to-metal contact, this makes borax one of the best fluxes around.
Borax is Sodium Borate DecaHydrate, at least that's how it occurs in nature. Note the ten water molecules associated with the stuff. When you first apply it as a powder, it sizzles and dissolves in its own water. It then rapidly resolidifies into a flower-like crystal, then slowly melts to a honey-like consistency. You can buy (or make) anahydrous borax, but I've found it reabsorbs moisture so fast that it's not terribly useful.
Anyway, after the first fold, I did the fold-weld thing until I had 120 layers. I started with 5 layers, doubled to 10, trippled that up to 30 with a tri-fold, doubled that to 60, and finally doubled that up to 120. At this point I had a roughly square piece of metal 2" on a side, about 1/2" thick. I needed a piece that was circular, about 3/16" thick, and as wide as possible, at least 3" for the pizza cutter wheel.
I could have just forged it to shape, but that would be boring. To get some patterns in the steel, I first used an angle grinder to carve some 1/8" deep by 1/4" wide lines on both sides of the billet in a tic-tac-toe shape, then took the billet over to the drill press and drilled in about 3/16" in the center of each of the resulting squares. (The stuff in this paragraph happened off-camera, sad to say. The ground-up and drilled billet looked pretty damn cool.)
This removal of metal results, when I flatten it out, in a pattern of bulls-eyes surrounded by a nice grid pattern of lines. Or at least so I hope. Can't really know how it came out until after the final etch, but I'm hopeful.
Having set my pattern, I heated it back up in the forge, re-fluxed to help reduce oxidation and to assist in tacking down any loose laminations, and flattened it out to the final dimensions in the power hammer, then did the final shaping on the anvil to taper out the edges a bit and to keep things aligned. A final heat and anneal, and it's off to the grinder.
I did some quick cleanup of the forge scale, and a quick etch in apple cider vinegar. Looks like the pattern is there, all right.
The final stock came at at a bit over 3" square, and after searching for the right size template to use, I found a can of Bush's beans that was just the right size to maximize the size of the circle. Hey, I tried to use my compass, but the lead just didn't show up on the steel. With a template, I can just outline with a sharpie all the metal I want to remove.
with 3hp and a 36 grit belt, I removed most of the material quickly. I'm having some problems keeping it perfectly round, as the blank turned out thicker in cross section along one axis -- it keeps wanting to be oval. I guess an oval pizza cutter would work, but I'm going to try to rig up a jig on the milling machine to make this perfectly round. Once that happens, I'll grind the bevels into the wheel, and then do the final polishing and grinding. whee!