Threaded Inserts - VERY stupid question

With dozens of drill bit types and thousands of sizes to choose from we'll explain the differences and help you choose the right drill bit for your application.

Anatomy of a drill bit:

Materials used to make drill bits:

• Carbon Steel -
• High Speed Steel (HSS) -
• Cobalt Steel -
• Tool Steel w/ Carbide Tips -
• Solid Carbide -

Coatings used on drill bits:

• Black Oxide - The most economical coating. Black oxide adds corrosion protection, increases tempering and stress relieving of the bit, reduces galling and chip welding, and aids in retaining drilling lubricants. Black oxide is suitable for drilling iron and steel but is not recommended for drilling aluminum, magnesium, or similar materials.
• Bronze Oxide - Bronze oxide increases tempering and stress relieving of the bit and is generally used alone to visually identify cobalt steel or with black oxide to identify better grades of high speed steel.
• Titanium Nitride (TiN) - A more expensive coating that increases the hardness of the bit and provides a thermal barrier resulting in increased production rates and longer tool life in harder materials. TiN also provides the same benefits as black and bronze oxide. TiN coated bits are suitable for drilling iron and steel as well as aluminum, magnesium, etc.

Drill bits are generally classified as Twist Drill, Counterbore, Countersink, Flat Bottom Boring, and Specialty. On our web site we have divided these into two categories:

• Drill Bits - Normally used with hand held drills or drill presses fitted with standard chucks. These machines use a key to tighten or loosen the clamping mechanism.
• Boring Machine Bits - Typically used in automated machinery such as drill banks or CNC machines fitted with tool holders or single size collets. These machines require tools to assemble and disassemble the clamping mechanism. Many boring machine bits are available in right or left hand rotation.

*Note that most standard drill bits can be used in automated machinery (with the proper adapter) and most boring machine bits can be used in a portable drill or drill press (assuming the chuck is big enough). We have only organized them in this fashion to make selection easier.

Twist Drills

General Description: Twist drill bits are the most common type of drill bit and are used for everyday drilling in all types of material. They are also the most confusing due to the sheer number of size, tip, and material specifications.

Length Designations: The length of a twist drill has much to do with its rigidity - a shorter bit will be stronger and less likely to wander or break but may not have the reach needed for all jobs. Twist drill bits for use in automated machinery have an actual length specification (e.g. 4-1/2") while most (not all) twist drills for use in portable drills are graduated length and use a name to specify the length range:

• Jobber Length: These are the most common twist drills and are a good compromise between length and strength. Jobber drills vary in length according to their diameter and typically have a flute length of 9-14 times the cutting diameter, i.e. a 1/2" jobber drill has a flute length of 4-1/2" (nine times the diameter) with smaller drills having a larger ratio.
• Mechanics Length: Shorter than jobber drills, mechanics length drills are named as such because they fit into tighter spaces and are less likely to break while still allowing a reasonable flute length.
• Screw Machine Length: Also called "stubby length", these are the shortest common drill bits. Originally designed for screw machines, many people prefer these due to their high strength and added working clearance.
• Extra Length: These are extra long drill bits (up to 18") with flutes extending the entire length of the bit. Extra length drills can be very fragile and easily broken so it's usually best to drill as deep as possible with a jobber or shorter bit before switching to an extra length drill bit.
• Aircraft Extension: Similar in length to extra length bits, aircraft extension drill bits emphasize reach over cutting depth and have a shorter flute length (about the same as a jobber drill). This makes the bit much stronger and less susceptible to bending and breaking.
• Silver and Deming: More than a length specification, Silver and Deming drill bits are 6" long with a 3" flute length and a 1/2" diameter shank. All Silver and Deming bits are over 1/2" cutting diameter, ranging from 33/64" to 1-1/2", and are primarily intended for use in a drill press.

Size Designations: Common twist drills for use in portable drills, etc. are available in fractional inch, wire sizes, letter sizes, and metric decimal millimeter. Twist drills for use in automated machinery are only available in fractional inch and decimal millimeter. See our Drill Bit Size Chart for the breakdown of fractional, letter, and wire sizes.

Tip Styles: Twist drill bits are available with different tip styles to suit various applications as outlined below:

• Conventional Drill Point: This is the most common tip style as seen on everyday general purpose drills. The tip angle is usually 118 degrees but can vary from 90° to high angle "Plexi Point" for use in acrylics. Conventional drill point drills are the most economical and are easily re-sharpened. Suitable for wood, non-ferrous metals and mild steel.
• Split Drill Point: This is an advanced drill point that prevents walking and provides improved penetration with less effort. Available in 118 or 135 degree angles, split point drill bits are better for drilling in curved surfaces or in alloy steels. They are more expensive and more difficult to re-sharpen than standard drill points.
• V-Point: This is a special high angle tip used on drill bits for automated wood boring machines. V-point drills are used to create thru-holes in sheet stock for dowels or other assembly hardware.
• Brad Point: Designed for creating blind holes in wood and other soft materials for shelf pins, dowels, etc. Bradpoints are also used for thru-holes in CNC applications where a conventional drill point would penetrate the table below the panel. Bradpoints have spurs on the outer edges to prevent splintering and chipping of the surface material as well as a center spur to prevent walking as the bit penetrates the surface.
• Fishtail Point: These special drill points form a reverse "V" in the tip and are designed for drilling into a surface at an angle without walking. They are commonly used as center drills in counterbores for furniture assembly where panels must be joined at right angles.
• Taper Point: These drill bits have a very large taper, extending far up the drill which creates a tapered hole. Primarily used for old style wood screws.

Flute Styles: Most twist drills have flutes to evacuate the chips at an unspecified angle, and are suitable for the majority of applications. Some specialty twist drills may be designated as "High Helix", "Fast Spiral" or "Low Helix", "Slow Spiral" for specific applications requiring higher or lower spindle speeds or feed rates.

Shank Styles: Twist drill bits designed for use in automated machinery have fixed diameter (usually 1/2" or 10mm) shanks, threaded shanks, or specialty shanks designed for certain machines. General purpose twist drills for use in portable drills have shanks the same diameter as the bit size (up to a certain diameter), larger diameter bits incorporate a reduced shank (either 1/4", 3/8" or 1/2") to fit into a standard drill chuck. Some bits have 3 flats on the shank to prevent spinning under high torque loads. Others have 1/4" hex shanks for use in a portable drill with a hex bit holder.

Materials: General purpose twist drills for use in portable drills are available in different grades of high speed steel as well as cobalt steel and solid carbide. Twist drill bits for automated machinery are available in carbon steel, high speed steel, carbide tipped, and solid carbide.

Coatings: General purpose drill bits are available with black oxide, bronze oxide, a combination of black and bronze oxide, and TiN coatings. Twist drills for automated machinery on our site are primarily for use in wood or plastics and are not coated.

Counterbore Drill Bits

General Description: Counterbore drill bits create a flat bottom blind hole with a smaller diameter center hole that penetrates through the material. The purpose of a counterbore is usually to conceal the fastener head (by covering the hole) or provide a recess to prevent the fastener from protruding above the surface of the material being drilled. Counterbores on our site are designed for use in wood or plastics and are not intended for counterboring steel.

Tip Styles: The cutting tip of a counterbore drill consists of one or more flat blades extending from the center drill to the outer edge. Counterbores are available with or without spurs (teeth) at the outer diameter of the bit. Counterbores with spurs on the outer edge prevent chipping and splintering on wood or laminated surfaces.