Wednesday, February 4th, 2015
After you have chosen a quality drill motor and Tungsten Carbide tipped bit, use these 10 simple steps to facilitate successful hard plate drilling:
Tip #10 is especially critical to safe drilling success. When you are drilling, watch the chippings and listen to the cutting tone. A change in tone will indicate that the sharp edge has gone or has stopped cutting*. When in doubt, inspect the bit more often rather than trying to push it through.
The efficiency of a safe drill bit on any particular hardplate can often be judged by the size, shape and color of the chippings coming from the hole. Some materials give a needle like or flaky chippings while others can give continuous spirals–it all depends on the ductility of the metal being drilled and the sharpness of the drill bit, as well as the speed and pressure applied.
”…a change to a hotter gray-blue color could indicate that too much heat is being generated…”
It is quite common to get chipping coming out which are blue in color while drilling some hard steels in the most efficient manner, but a change to a hotter gray-blue color could indicate that too much heat is being generated at the cutting face. The increase of temperature in the cutting region may then cause the safe drill bit to become easily damaged and the safe bit will have to be scrapped. The speed and pressure should be reduced to lessen the overheating. Be careful, if you stop drilling halfway through, you can sometimes leave a surface which is actually harder to cut than the original material.
*You should always stop drilling when the sharp edge has gone. If you continue the tip could deteriorate and re-sharpening may not be possible. If a bit has lost its sharp edge, you should sharpen it using a green grit wheel.