Anthony Cardasco contributed: >I am assuming you don't have access to a bandsaw, lathe or milling machine. >One "by hand" method you could use is to take a square bar of brass or >aluminum and file off one corner to make a 45 degree chamfer ....
A word of caution when removing large amounts from one edge of a hard-drawn metal bar or even sawing a gnomon out of thick plate material. The outer skin of the metal will have enormous stresses contained within it resulting from being drawn through shaped dies. Because these stresses are all balanced out the uncut bar stays straight. Remove half a diameter or cut out your gnomon shape leaving an existing straight edge as the style - and then wonder why it has gone banana shaped? There are two ways round this: 1. Anticipate that the straight edge will bend - usually away from the cut line - and allow some extra for filing/machining it straight again. 2. 'Anneal' the bar before cutting to allow all those internal stresses to relax. For brass/copper/bronze this involves heating to a visible red then allowing the metal to cool. The rate of cooling is unimportant. Many people 'pickle' the hot metal in 10% sulphuric acid at this stage to remove oxide scale. I prefer to use a big stoneware jar of ordinary malt vinegar. The fumes and the liquid are far less hazardous but the process is equally effective. Small parts can be retrieved by hand if dropped into the solution. Aluminium alloys can be annealed by rubbing ordinary soap on the metal and then heating evenly until it turns black. Annealing also makes the metal soft and bendable without cracking so if you want it left in a hard condition it's method 1. for you. Best Wishes Tony Moss.
