I need to make a 3 foot tall cowbell. Can you help me? :)
Sure, we'll need pi*diameter*3' of copper for the body, plus a couple of extra square feet for the top. We'll need a couple of pounds of solder for the seam, and I can make a bitchin' clapper out of an old sledge hammer. :)
2006-03-08 01:43 am (UTC)
Re: giant cow bell
oooo Excellent! Is there a place out by you that would have copper sheets? Not sure what guage it would have to be not to be easily damaged by that sort of clapper... It's been a while since I have done any metal work. I need to get this done sometime before August. Would I be able to steal your time to do this one weekend before then?
We should probably talk about what you want this for -- if you're just looking for a big bell, I can make one pretty simply from an old propane gas tank. Honestly, copper, while used for small cow bells, isn't going to scale up without drastically increasing the thickness of the metal, and copper isn't cheap nowadays. If you want something for the look, it would be easier to modify an existing bell shape (such as an old 100 lb propane tank); if you want the sound that's pretty easly to arrange (just need to dampen the reverberation a bit).
Checking, there's nothing that says it *has* to be made of copper to be called a cow bell, so we can open up the construction metals to a bunch of cheaper stuff, including iron sheet, possibly from the scrapyard (think pre-patina'd).
(*screams in horror*) Did the man I know as blackanvil
just use the word "bitchin'?!"
Yep. You *do* know I was born in the San Francisco area of California. Valley-Smith Doug.
someone clearly lives in the south where they redefined Pi to be 3.
becasue if god was a proper holy trinity, it would be circumference divided by the body of the diameter ;)
if you look again, you'll see I specified pi times the diameter (2r) of the bell (assuming a roughly cylindrical bell) time 3', the specified height diameter.
Though I do note that for a rough materials estimate, for something of this size, pi=3 gets you in the ballpark, and you always add 10% or a bit more when computing a materials estimate. Personally, though, I tend to leave pi at the number of significant digits I'm measuring to, and ignore the rest of the digits.
I was pointed in your direction via vvalkyri
What tools and techniques do you use to change the 'false edge' on a blade to a real edge? When does the angle of the false edge become too steep to warrant such an attempt?
2006-03-08 02:42 pm (UTC)
false edge to real edge
First off, technically a "false edge" can be a real edge -- in a working knife or sword, a false edge is often as sharp as the real edge, though it doesn't have to be, and may just be a decorative bevel or one put on to reduce the weight of the blade.
Assuming I needed to turn a dull false edge to a 'real edge,' or I wanted to add a fully-sharp false edge to an existing blade, I'd use a belt grinder (I use two, a 5 hp homebuilt running at about 5000 feet per minute, and a Bader II 2hp with different drive wheels for speed control) to remove the metal required. Since presumably you're talking about an already-hardened and tempered blade, I'd use the BIII with a small drive wheel, and cool it early and often to avoid distempering the blade -- and switch to the water-cooled grinding wheel (old waterstone setup or Makita doughnut grinder) for the tip.
As I'm used to profiling blades from scratch, I'd have no problem regrinding a blade no matter how steep the bevel is. About the only thing that would stop me from sharpening up a false edge would be aesthetics, utility, or legality. Changing the angle or even the style of bevel is part of knifemaking. Even if I didn't want to change the grind lines, I could make a shallow, steep false edge very sharp by using, say, a 4' contact wheel and hollow grinding it.
Hope that answers your question.
2006-03-08 05:24 pm (UTC)
Re: false edge to real edge
Two of the three blades I'm considering it for are clip-point bowies. A Spyderco Perrin
and a 6" blade Randall Model 5 Camp and Trail
. The third is a spear-pointed survival knife. The Randall and survival knife definitely have the grinds for it. I'm not so sure about the Perrin. Unfortunately, my tools consist of a 1" X 30" belt grinder with a 5" contact wheel, a dremel multi-tool, some files, and a Spyderco Sharpmaker.
Legality is not an issue in my state. And I'm thinking having two edges will be useful in a camp knife.
please compare/contrast the differences/qualities of anneal, vs, harden, vs temper ; and why it's important to anneal a 51200 ball bearing or other suspect material before welding or heating to absurd ranges - in particular rare earth magnets. :)
Joe, I'm pretty sure you know the answers to those already, but . . .
annnealing is softening and removing the stresses from forging operations, hardening is making the blade harder (and more brittle), and tempering is relieving the stresses from the hardening and softening the blade to increase toughness.
I've heard, but never personally seen or know anyone who'll say it happened to them, that the larger ball bearings, 51200 or otherwise, need to be annealed or they'll explode. The process of heating to welding temperatures should make the steel plastic enough that any stresses should be relieved in the process -- assuming you're doing it right. You never want to "shock" tool steel from a cold state to uber-hot, that would be just asking for micro-fractures and other problems. Leaving the steel in a hot but shut off forge for a minute should do the job; or heating in a cold forge. But an "explosion" seems unlikely unless you're really doing something stupid (like taking a 3" ball bearing from a liquid nitrogen dip to a fully-hot ready-to-forge-weld forge.)
You should never put a rare-earth magnet in a forge. not only are they toxic, not only can they explode, but they can contaminate your forge with exotic chemicals that will make welding a bitch, if not impossible. Oh, and if you're talking about the United Nuclear uber-magnets, I'd not want to take one of those into the workshop -- there's a lot of loose iron around, some of it quite sharp.