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A Dozen types of drill bits make it harder for us to choose one. To pick just the one you need, you should know the different types
Before getting on the details for the types of drill bits, you need to know the materials used to make them.
- Cobalt Steel
- Solid Carbide
- HSS – High-Speed Steel
- Tool Steel / Carbide Tip
You may also like to read the drill bits reviews .
Many factors categorize drill bits. Like its coating, constructional material, length, cutting edge, Tip Style, Flute style, shank style, Use on different objects.
Types Based On Coating:
1. Black Oxide: Black oxide provides corrosion protection. It increases tempering, relieves stress, reduces chip welding and galling, aids in retaining lubricants and they are very economical.
2. Bronze Oxide: It also increases tempering & helps to reduce stress. The bronze oxide is often used with black oxide.
3. Titanium Nitride (TiN): It is comparatively expensive but very effective. Besides increasing hardness, it also provides production increasing thermal barrier and longer lifetime. TiN also gives you all other facilities that black and bronze oxide can provide.
Types Based On Length:
1. Jobber length: These are well-balanced between strength and length. They vary in the diameter.
2. Mechanics Length: Typically shorter than jobber length. But they fit in narrow and tighter space.
3. Screw machine length: Also called as stubby length. Shortest among the normal drill bits yet preferred for its strength and working clearance.
4. Extra length: They are comparatively longer than other bits with their flutes extending the entire length. Though extra drill bits are useful to make lengthier holes, they are very fragile. It is wise to use a jobber before using extra length drill bit to make a hole.
5. Aircraft Extension: the length is similar to extra length drill bit. But, their flute length is shorter. That’s why aircraft extension drill bits are stronger & less susceptible to breaking and bending. They are used for reaching over cutting depth.
6. Deming and Silver: 6” in length, but flute length is 3”. Primarily used in a drill press.
Types Based On Drilling Point:
1. Conventional drilling point: These are the most common tips you’ll find. Tip angle is 118 degrees in most cases. They are affordable and economical. Conventional bits are easily re-sharpened that’s why they are so preferable.
2. Split drill point: This advanced version drill bit prevents walking & improves penetration with lesser effort. The angle is between 118-135 degrees. They are comparatively expensive, and re-sharpening is more complicated than convenient drilling point.
3. V Point: This high angle bit is often used in the automated wood boring machine. V point creates thru holes in sheets for dowels and other assembly parts.
4. Brand point: Brand points are used to create blind holes in wood and other thin or soft material to use for shelf pins, dowels, etc. They have spurs on their outer edge which prevents splintering & chipping of the surface.
5. Fishtail points: This tip is like reverse “V.” Fishtails are used to drill on a surface at a particular angle without walking.
6. Taper point: They have a large taper which extends far up to the drill that creates a tapered hole. Taper point works best for old style screws.
General types of drill bits based on structure and function:
1. Counterbore Drill Bit: They create a flat bottom blind hole with small diameter center hole which penetrates through the material. The tip has one or more than one flat blades that extend from the center to the edge. Spurs on the outer edge resist splintering or chipping on wooden and laminated surface.
Counter bore can be both with or without flutes. They have a straight shank and same radius as a center drill. Most of the counter bores do not have any special coating.
2. Countersink Drill Bit: Countersink bits usually create a tapered surface hole with a small center hole which penetrates through the material. The intend to use a countersink bit is to allow any tapered head fastener so that it sits flush with the surface.
They have more than one flat blades that extend from the center drill to the edge. The angle is between 60-120 degrees. Except for the center drill, some countersink doesn't have flutes, and others are patented similar to the twist drill with a removable center drill. They have a straight shank, and the radius is same as a center drill.
3. Flat Bottom Boring Bit: Similar to counterbore, but they don’t include a center drill. These bits are used to make large diameter thru hole. The thru hole bits are used on locks, wiring holes, door knobs, etc. They can make flat bottom blind holes which are suitable for European style hinges. Most common type flat bottom boring bits are:
- Forstner bits
- Door hinge bits
- Three wing drills
- Spade bits
- Mortising Bits
Types based on use in material
1. Iron: To use - Black Oxide or TiN
2. Steel: To use: TiN or Black Oxide
3. Aluminium: To use - TiN
4. Magnesium: To use: TiN
5. Not to use: Black Oxide
5. Cobalt Steel: To use: Bronze Oxide
6. Wood: To use: Counter bore
7. Plastic: To use: Counter bore
The cutting tip has one or more flat blade that extends from the center to edge. They are available in both with or without spurs. Larger bits don’t have flutes. Most of the big boring bits have a solid hexagonal shank. Hexagonal Shank prevents the bits from spinning in the chuck while it’s under excessive pressure.