[China Aluminum Network] 1. View color. The surface of pure aluminum that has been formed into an oxide film is milky white, cast aluminum, and mixed aluminum are grayish black. The surface without oxide film is transparent and bright white, and some also have pink or gray-black hanging cream.
2. Measuring resistance. Oxidation film has been detected with resistance and is not conductive at normal pressure. Non-oxide film can conduct electricity when detected.
3. Scratches, the surface of the oxide film that has formed is very hard, slipping when scratched with a needle, no scratches, the surface without oxide film is very soft, there are resistance and scratches when scratching with a needle.
4. Hearing, a cracking sound will be generated when the oxide film is formed, and a muffled sound will be generated when the oxide film is not generated. 5. Coloring test. Oxide films can be quickly colored in the dyeing solution, and no oxide film is dyed in the dye solution.
Forstner bits, flat-bottomed to drill holes in wood materials, they can cut on the edge of a block of wood, and can cut overlapping holes; for such applications they are normally used in drill presses or lathes rather than in hand-held electric drills. Because of the flat bottom of the hole, they are useful for drilling through veneer already glued to add an inlay.
The bit includes a center point which guides it throughout the cut (and incidentally spoils the otherwise flat bottom of the hole). The cylindrical cutter around the perimeter shears the wood fibers at the edge of the bore, and also helps guide the bit into the material more precisely.
Forstner bits have radial cutting edges to plane off the material at the bottom of the hole. The bits shown in the images have two radial edges; other designs may have more. Forstner bits have no mechanism to clear chips from the hole, and therefore must be pulled out periodically.
Forstner Bits,bosch forstner bits,colt forstner bits
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