How to Buy Drill Bits on eBay

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How to Buy Drill Bits on eBay

When cutting a hole on a surface, using a drill often comes to mind. Although the power tool is what drives the cutting, a certain part called drill bit is the one at the point of contact and doing the actual drilling. Drill bits are a very important part of a drill, and the precision and length of the cutting as well as the shape of the hole depends largely on the type of drill bit that is used. Understanding the aspects of drill bits is a good way to know how they can function to one's advantage. There are a large number of drill bit types, and each type is used for a specific purpose. Drill bits are also categorised based on the material they are made of and their type of coating.

There are drill bits for sale on eBay, and many of them are sold in sets. It can be quite bewildering to find the right drill bit or the right combination of drill bits to buy because of the many options. However, knowing the different types based on intended application, along with the types of material and aspects of drill bits can take the guesswork out of buying.

Drill Bits Explained

To connect to a drill, a drill bit has a shank that attaches to the chuck of a drill. On the other end of the drill bit are edges that do the cutting. Drill bits usually create a cylindrical hole, but a specially-shaped bit can create a non-circular cross section, such as a square cross section.

Aspects

A drill bit has several characteristics worthy of consideration. The spiral or the rate of twist in the drill is in charge of the rate at which the chips are removed. When in need of taking away large amounts of swarf in high feed rate applications that have low spindle speeds, a fast spiral drill bit is used.

The point angle is the angle that forms at the top of the bit. For drilling soft materials, a bit with a sharper angle is required, while harder materials need a larger point angle. The lip angle, on the other hand, provides a degree of support, depending on its size, to the cutting edge. The greater the size of the lip angle the more aggressive the cut of the bit.

The length of a bit is one important consideration when buying a set of drill bits. The length not only determines how long a hole can be drilled but also how accurate the hole made and how stiff the bit would be. The different varieties of drill bits based on the length are: stub length or screw length, jobber length, and taper length.

Type of Material

Depending on its application, a drill bit can be made of different types of materials. Buyers should consider the material before tackling any task. A drill bit can be made of steel, carbide, or polycrystalline diamond.

Steel

A steel drill bit can actually be made of a low carbon, high carbon, high speed, cobalt, and hi-moly steel. The cheapest of the five is made of soft low carbon steel, which is used only for drilling wood. This type of drill bit, however, does not hold an edge well, needs to be sharpened frequently, and eventually loses it function when used in hardwoods.

The high carbon steel is sturdier than its low carbon counterpart and can be used in both wood and metal. High speed steel is more resistant to heat than carbon steel, and a high speed steel bit is used in wood, metal, and other materials, with the advantage of great cutting speed compared to a carbon steel bit.

A cobalt steel alloy, on the other hand, is used for stainless steel and other hard materials. It remains tough even at high temperatures, but they are more brittle than the high speed steel variety. Hi-moly steel has a nitro-carburized finish, allowing it to perform without losing its sharpness at much higher temperatures during frictional heating.

Carbide

Carbides are very reliable. Due to their hardness they can drill any material while maintaining their edge as opposed to other bits. However, carbide drill bits are very expensive, and with smaller sizes, it can be very difficult to fit carbide tips. Carbide can be used to make up the whole drill bit or used as a tip of the drill bit. Some industries require the use of carbide bits when drilling several holes with less than 1 mm.

Polycrystalline Diamond (PCD)

Composed of a layer of diamond particles, polycrystalline diamond bits are the hardest of all bits. The layer of diamond is approximately 0.5 mm thick, which is bonded as a sintered mass to a tungsten carbide support. PCD bits are used in industries like automotive and aerospace to drill hard-yielding aluminium alloys, carbon fibre reinforced plastics, and other materials.

Coating

A drill bit can have different coatings. One type of coating is black oxide, which is inexpensive and allows lubricity as well as corrosion and heat resistance. Another type is titanium nitride, which is used in coating high-speed steel bit. Titanium aluminium nitride, on the other hand, can make a tool last five times longer than its regular life. Diamond powder is used for drilling stones, tiles, and other abrasive materials.

Main Types of Drill Bits

Drill bits can be classified into three main types. The main types are universal bits, metal bits, and wood bits. There are other types of drill bits that do not fall in any of the mentioned category.

Universal Drilling Bits

As its name suggests, a universal drill bit can be used to create a hole in metal, wood, plastic, and other materials. It can be further categorised into twist drill bits, step drill bits, unibits, and hole saws. The twist drill bit is characterised by a cutting point with helical flutes that serve to lift swarf out of the hole. A twist drill bit that has a point angle of 118 degrees is widely available and can be used with wood, metal, plastic, and other materials. However, this bit does not produce results as optimal as the required angle for each material like the 90-degree variety for soft plastics and 150-degree variety for steels and other.

The step drill bit features a tip that has a ground diameter to prevent the bit from clogging during the drilling session. The unibit, which is roughly conical and features a stair step profile, is great for drilling a variety of hole sizes. The hole saw, on the other hand, is an open cylinder with saw teeth to make large holes in thin material.

Metal Drilling Bits

There are many types of metal drilling bits. Central bits are utilised to make a starting hole in metals for a larger-sized drill bits. They are used in spotting hole centres and creating holes for lathe centres. Another type is the core drill bit, which are two bits: one for enlarging an existing hole, and another, a hollow cylindrical bit, is used for extracting a core.

A countersink bit, a third type of metal bit, is used to cut a conical hole cut into a manufactured object. Another type of metal bit is the ejector drill bit; it creates deep holes with medium and large diameters. A gun drill bit is different in that it injects a right liquid or compressed air to the cutting face via the hollow body of the drill.

Wood Drilling Bits

One type of wood bit is the lip and spur drill bit, an optimised twist drill to make it suitable for woods. This type of wood bit features a spur with a sharp point, which allows it to not wander away during drilling. A wood spade bit is flat and has a centring point and dual cutters. Because a wood spade bit produces splinters as it comes out of the workplace, its cutters often have spurs to make a cleaner hole. Another type of wood bit is the spoon bit; it has a spoon-like point having a cutting edge on the end. It is not used with a power drill but with the traditional brace.

A forstner bit, on the other hand, is used with a power tool to drill flat-bottomed circular cut into wood. It is great for drilling through veneer to add inlay. Another type is the centre bit, which is a tapered screw thread that can have two spurs or two radial cutting edges. An auger bit is a type of wood drilling bit that is used in hand braces, and it has a long, deep spiral flute to effectively remove chips. The most expensive is the indexable drill bit, which creates holes not deeper than five times the diameter of the bit

Other Types of Drilling Bits

Other types of drilling bits include diamond core bits, masonry drill bits, glass drill bits, PCB through-hole drill bits, and installer bits. Diamond core bits have a steel shell with diamonds layered in metal parts on the cutting edge. Used at relatively low speeds, they are a combination of router and drill bit. A masonry drill bit, on the other hand, is another variation of a twist drill bit. It used with a hammer drill to break up the masonry while the rotation scoops away the dust. Glass drill bits use a spade-shaped carbide point to bore a hole in glass.

PCB through-hole drill bits are made of highly abrasive fibreglass to drill several small holes. Lastly, there are the installer bits that come either as fishing bits or flexible shaft bits. A fishing bit can be used with a hand-portable power tool and allows hooking of a wire, while a flexible shaft bit has a long, flexible shaft with a tiny twist bit at the end, allowing it to curve inside a material.

Summary of Drill Bit Types

The table below shows the different main types of drill bits and their subtypes. It also presents the characteristic of each drill bit sub type.

Drill Bit Main Type

Drill Bit Sub Type

Characteristics

Universal Drilling Bit

Twist Bit

A cutting point with helical flutes that serve to lift swarf out of the hole

 

Step Bit

Has a ground diameter to prevent the bit from clogging during the drilling session

 

Unibit

Roughly conical and features a stair step profile; great for drilling a variety of hole sizes

 

Hole Saw

Open cylinder with saw teeth to make large holes in thin material

Metal Drilling Bit

Central Bit

Makes a starting hole in metals for a larger-sized drill bits

 

Core Bit

Two classes: one for enlarging an existing hole and another, a hollow cylindrical bit; used for extracting a core

 

Countersink Bit

Used to cut a conical hole cut into a manufactured object

 

Ejector Bit

Creates holes with medium and large diameters in drilling deep holes

 

Gun Bit

Injects liquid or compressed air to the cutting face via the hollow body of the drill

Wood Drilling Bit

Lip and Spur Bit

Optimised twist drill to make it suitable for woods

 

Wood Spade Bit

Features a spur with a sharp point allows it to not wander away during drilling

 

Spoon Drill Bit

Has a spoon-like point that has a cutting edge on the end used with a brace

 

Forstner Bit

Used with a power tool to drill flat-bottomed circular cut in wood

 

Centre Bit

A tapered screw thread that can have two spurs or two radial cutting edges

 

Auger Bit

Used in hand braces; has a long, deep spiral flute to effectively remove chips

 

Indexable Bit

Creates holes not deeper than five times the diameter of the bit.

Other Types

Diamond Core Bits

Steel shell with diamonds layered in metal parts on the cutting edge; combination of router and drill bit

 

Masonry Bit

Variant of twist drill bit used with a hammer drill to break up the masonry while the rotation scoops away the dust

 

Glass Bit

Spade-shaped carbide point and used to bore a hole in glass

 

PCB Through-Hole Bit

Made of highly abrasive fibreglass to drill several small holes with about one millimetre or below

 

Installer Bits

Fishing bit: used with a hand-portable power tool, and allows hooking of a wire; flexible shaft bit: long, flexible shaft with a tiny twist bit, allowing bit to curve inside a material

The table above is a quick reference that is useful when looking for the right drill bits for a particular application. Buyers should also be aware that many drill bits online are sold in sets.

Buying Drill Bits on eBay

There are so many drill bits that can be bought on eBay. Most drill bits available on the site come in sets, often with a single type in different lengths. The information about the different types of drill bits guides you to the right drill bit among the sea of drill bits on the site. Moreover, it is easy to search for products on eBay. Simply type in the keywords such as "twist drill bits" or "forstner bits" into the search bar, and you are presented with a variety of options for the product. Furthermore, you can filter your search based on your preferences.

When buying on eBay, do not just look for the product with the lowest price, but also look for reputable sellers that have the great feedback from buyers. These sellers give you an assurance of a smoother and faster transaction.

Conclusion

Drill bits are a crucial item in many types of work, including woodworking, metalworking, and masonry, among many others. To know how a drill bit functions, it is important to know its four most important aspects: its spiral, point angle, lip angle, and length. The material a drill bit is made of can ranges from different varieties of steels, carbide, to, in rare cases, a polycrystalline diamond. The coating further strengthens the drill bit.

The main types of drill bits are categorised based on the intended application. There are wood drill bits, metal drill bits, and the universal drill bits. Others that do not fit into the category are used for masonry, glass, and more. Drill bits come in a variety of lengths, brands, and types, and it is important to have be able to distinguish between each. Whether drilling wood, metal, and other surfaces, the exact type of drill bit for the job provides users with a precise and smooth drilling session.

 
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