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Because you presumably want your hole to be the right size, not too small or too big.
Because you presumably want your hole to be the right size, not too small or too big.
Because you presumably want your hole to be the right size, not too small or too big.
Most metals are initially drilled with a narrower drill, forming a pilot hole. Then the right size drill is used to complete the drilling of the hole by widening the pilot hole.
A diamond core drill, slow and easy, with plenty of water.
Drill bits for boring into glass can be purchased from a number of outlets. The best prices can be found at Home Depot and the Amazon website. They can often be found on eBay too.
That's a tough task for a battery operated tool. You really need a hammer drill. There's a nice Milwaukee cordless hammer drill at Sears but it costs $350. My corded hammer drill cost only $79. To me that is a huge difference for the convenience of cordless.
It all depends on what you are constructing. If the hole is required for some kind of fastener, if it is too small the fastener will not slide through. If to slack, the unit may fail when put into use, by allowing movement and wear, causing early fatigue.During specialist construction (say for aircraft) some holes are drilled slightly under size and then reamed out, for a perfect fit.For wood screws, the pilot hole must allow enough material for the thread to grip, but without pinching the screw, making it difficult to tighten up.
They love suet, peanuts, and sunflower seeds. If you drill big holes in a log fill them with peanut butter and hang it from a tree they will be your best friend,
A titanium or cobalt drill bit.
Yes, just use a clean drill bit. Make sure it is free of any oils or lubricants. Wash it well with soap and water. A brand new bit is probably your best bet.
Coated carbide is the best. Uncoated is next.