A step drill bit with a straight flute is called a counter-bore step drill bit while a step drill bit with a twisted flute is called a countersink step drill bit. The flute or the groove profile serves as a channel system for collection and chip removal during drilling.
I have found the step drill bit to be a valuable tool with its ability to replace numerous twist bits, deburrers, and reamers. There are a number of reasons you should use a step drill bit for drilling into sheet metals.
I have compiled a list of reasons I recommend every DIY enthusiast to add step drill bits to their toolbox.
Multiple Diameters: With multiple diameters, a step drill bit saves you from the hassle of changing drill bits when you need to drill a lot of holes of different sizes. You can use a step drill bit to drill holes of different diameters.
Selt-tapping tip: Step drill bits have self-tapping tips, which allow you to drill without drilling a pilot hole in thin materials.
Flute: Flute on a step drill bit allows for easy removal of waste materials which prevents clogging as well as heating up of the drill bit.
Reaming: Step drill bit gives you smooth edges on the holes instantly thus eliminating the need for a reamer.
Deburring: You can also use a step drill bit to deburr the hole you have drilled by lightly touching each side of the hole with bevel of the next step.
And although step drill bits have a range of benefits, there are a few downsides as well.
Twist Drill Bit
The twist drill bit is the type produced in largest quantity today. It comprises a cutting point at the tip of a cylindrical shaft with helical flutes; the flutes act as an Archimedean screw and lift swarf out of the hole.
History
The twist drill bit was invented by Steven A. Morse of East Bridgewater, Massachusetts in 1861.The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar (giving the tool its name) to produce the helical flutes. Nowadays, the drill bit is usually made by rotating the bar while moving it past a grinding wheel to cut the flutes in the same manner as cutting helical gears.
Twist drill bits range in diameter from 0.002 to 3.5 in (0.051 to 88.900 mm) and can be as long as 25.5 in (650 mm).
The geometry and sharpening of the cutting edges is crucial to the performance of the bit. Small bits that become blunt are often discarded because sharpening them correctly is difficult and they are cheap to replace. For larger bits, special grinding jigs are available. A special tool grinder is available for sharpening or reshaping cutting surfaces on twist drill bits in order to optimize the bit for a particular material.
Manufacturers can produce special versions of the twist drill bit, varying the geometry and the materials used, to suit particular machinery and particular materials to be cut. Twist drill bits are available in the widest choice of tooling materials. However, even for industrial users, most holes are drilled with standard high speed steel bits.
The most common twist drill bit (sold in general hardware stores) has a point angle of 118 degrees, acceptable for use in wood, metal, plastic, and most other materials, although it does not perform as well as using the optimum angle for each material. In most materials it does not tend to wander or dig in.
A more aggressive angle, such as 90 degrees, is suited for very soft plastics and other materials; it would wear rapidly in hard materials. Such a bit is generally self-starting and can cut very quickly. A shallower angle, such as 150 degrees, is suited for drilling steels and other tougher materials. This style of bit requires a starter hole, but does not bind or suffer premature wear so long as a suitable feed rate is used.
Drill bits with no point angle are used in situations where a blind, flat-bottomed hole is required. These bits are very sensitive to changes in lip angle, and even a slight change can result in an inappropriately fast cutting drill bit that will suffer premature wear.
Long series drill bits are unusually long twist drill bits. However, they are not the best tool for routinely drilling deep holes, as they require frequent withdrawal to clear the flutes of swarf and to prevent breakage of the bit. Instead, gun drill bits are preferred for deep hole drilling.
What type of wood drill bit should you use for what job?
Drilling a hole into a wooden plank isn't an impossible job even for the beginning DIY-er. On the other hand, there's drilling wood and there's drilling wood. Are you screwing a few planks together, or are you building an entire garden shed? These jobs call for different types of wood drill bits, since they come in all kinds of shapes and sizes. After reading this article, you'll know exactly which wood drill bit you'll need for your job, so you're guaranteed a nice result.
