Drill bit shank

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The shank is the end of a drill bit grasped by the chuck of a drill. The cutting edges of the drill bit contact the workpiece, and are connected via the shaft with the shank, which fits into the chuck. In many cases a general-purpose arrangement is used, such as a bit with cylindrical shaft and shank in a three-jaw chuck which grips a cylindrical shank tightly. Different shank and chuck combination can deliver improved performance, such as allowing higher torque, greater centering accuracy, or moving the bit independently of the chuck, with a hammer action.

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Brace shank

Brace drill bit shank Drill shank brace.jpg
Brace drill bit shank

This shank was common before 1850, and is still in production. At first, the tapered shank was just rammed into a square hole in the end of the drill. Over time, various chuck designs have been invented, and modern chucks can grasp and drive this shank effectively.

It has been difficult to find a reference to the included angle of the taper, but 7 different bits were measured, and they all had an included angle of 8 ± 0.25 degrees.

Straight shank

Straight drill bit shank Drill shank round.jpg
Straight drill bit shank

The straight shank is the most usual style on modern drill bits, by number manufactured. The whole of the drill bit, shaft and shank, is usually of the same diameter. It is held usually in a three-jaw drill chuck. Bits of diameter too small to grip firmly can have straight shanks of larger diameter than the drill, which can be held firmly in a standard size collet or chuck. Large drill bits can have straight shanks narrower than the drill diameter so that they can be fitted in chucks not able to chuck the full diameter. Such a drill bit is called a reduced-shank or blacksmith's drill. For example, this allows a 12-inch (13 mm) bit to be used in a pistol-grip drill's 38-inch (9.5 mm) chuck. One particular type of reduced-shank drill bits are Silver & Deming (S&D) bits, whose sets run from 916-inch (14 mm) to 1+12-inch (38 mm) drill body diameter with a standard 12-inch (13 mm) reduced shank for all. This allows drill presses with 12-inch (13 mm) chucks to run the larger drills. S&D bits are 6 inches (150 mm) long with a 3-inch (76 mm) flute length. The name comes from a company in Salem, Ohio that broke up into other companies circa 1890; bits of this design were popularized by that company.

Hex shank

Hex drill bit shank Drill shank hex.jpg
Hex drill bit shank

The flats of a hex shank can either be machined on a round shank, as in the photograph, or be the natural flats of hex bar stock. A hex shank can be grasped by a 3-jaw drill chuck or held in a chuck specifically for hex shanks. Quarter-inch hex shanks are common for machine screwdriver bits and have spread from that application to be used for drill bits that are compatible with screwdriver machinery.

  • A special 3c or 5c HEX collet must be used.

SDS shank

SDS-plus drill bit shank SDS-Plus.jpg
SDS-plus drill bit shank
SDS-max drill bit shanks SDSmax.jpg
SDS-max drill bit shanks

The diameter of an SDS and SDS Plus shank is 10 millimeters. The SDS Max is larger with an 18 mm shank diameter, while the SDS Quick has a smaller 6 mm shank diameter.

The SDS shank has the advantage of fitting into a simple spring-loaded chuck, so that bits are simply pushed into the chuck without tightening. This shank and the chucks made for it are especially suited to hammer drilling with masonry drills in stone and concrete. The drill bit is not held solidly in the chuck, but can slide back and forth like a piston; it does not slip during rotation due to the non-circular shank cross-section, matching the chuck. The hammer of the drill acts to accelerate only the drill bit itself, and not the large mass of the chuck, which makes hammer drilling with an SDS shank drill bit much more productive than with other types of shank.

Rotational drive uses the sliding keyways that open to the end of the shank, which mate with keys in the chuck. The smaller indentations that do not open to the end are grasped by the chuck to prevent the drill bit falling out. The hammer of the drill hits the flat end of the shank. The shank must be lubricated with grease to allow it to slide in the chuck.

There are four standard sizes of SDS: SDS Quick, SDS-plus (or SDSplus or SDS+), SDS-Top and SDS-max. SDS-plus is the most common by count of tools manufactured, with masonry drills from 4 mm diameter to 30 mm (and from 5/32" to 1-1/4") diameter ordinarily available. The shortest SDS-plus masonry drill bits are about 110 mm overall length, and the longest 1500 mm. SDS-max is more common for larger rotary hammers and chipping guns, and common sizes start at 12 inch (13 mm) diameter up to 1+34 inches (44 mm) diameter. Standard lengths are 12 to 21 inches (300 to 530 mm). SDS-Top has been largely phased out in North America and is not common except for older tools. Hilti's TE-S system is similar to these SDS systems, but is designed for chipping only (no rotation) in tools for applications larger than could be handled by SDS-Max (e.g. demolition of concrete walls or floors).

The SDS bit was developed by Hilti and Bosch in 1975. The name comes from the German : Stecken – Drehen – Sichern ("Insert – Twist – Secure"). In German-speaking countries the back-formation Spannen durch System ("Clamping System") is used, though Bosch uses "Special Direct System" for international purposes. [1] [2]

Triangle shank

Triangle drill bit shank Drill shank triangle.jpg
Triangle drill bit shank

The triangle shank is almost always made by machining three flats on round bar stock. It is intended as a minor modification of a straight shank, still allowing it to be held in a 3-jaw drill chuck, but allowing higher torque transmission and limited slipping.

Morse taper shank

Morse taper drills, from 13.5mm (with the No. 1 Morse taper shank) through to a 30mm drill (No. 4 morse taper shank) DrillsMorseTaperShank1234.jpg
Morse taper drills, from 13.5mm (with the No. 1 Morse taper shank) through to a 30mm drill (No. 4 morse taper shank)
Morse Taper Drill Bit Shank Drill shank morse.jpg
Morse Taper Drill Bit Shank

The Morse taper twist drill bits pictured right are used in metalworking. The full range of tapers is from 0 to 7.

The Morse taper allows the bit to be mounted directly into the spindle of a drill, lathe tailstock, or (with the use of adapters) into the spindle of milling machines. It is a self-locking (or self holding) taper of approximately 5/8" per foot [3] that allows the torque to be transferred to the drill bit by the friction between the taper shank and the socket. The tang at the end of the taper provides a positive drive of the drill when the taper fails to grip. [4] Many believe that the tang is there for the purpose of ejecting the tool from the taper but as not all tools have a tang (e.g. a centre lathe centre) these can still be ejected despite not having the tang.

The arbor of a drill chuck is often a Morse taper and this allows the chuck assembly to be removed and directly replaced with the shank of a Morse taper drill bit. A range of sleeves may be used to bring the size of the smaller Morse tapers up to the size of the drive spindle's larger taper. Sockets are also available to extend the effective length of the drill as well as offering a variety of taper combinations.

The detail image shows a Morse taper shank on a 16 mm diameter drill bit.

Square shank

Square taper drills were also used for large ratchet drills, for drilling large holes, or in thick plate. These bits would fit straight into a ratchet drill, and the ratchet drill would be used against a strong arm, for pressure to push the drill into the work piece.

Threaded shank

Some drills, wire wheels, etc. use a threaded shank. One example is cylindrical wire wheels meant to be pushed into a pipe of some sort to clean the inside of the pipe, but some ordinary, but mostly rather large, wood drills have threaded shanks as well.

Small (about 14 inch or 6.4 millimetres diameter) threaded drill bits and countersinks are common in aircraft metal work. Threaded drill bits may be held in drills meant to reach into very tight spaces, and threaded countersink cutters are widely used (along with finely adjustable depth stops) to create holes which put a matching rivet directly flush with the surface.

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Router (woodworking)

The router is a power tool with a flat base and a rotating blade extending past the base. The spindle may be driven by an electric motor or by a pneumatic motor. It routs an area in hard material, such as wood or plastic. Routers are used most often in woodworking, especially cabinetry. They may be handheld or affixed to router tables. Some woodworkers consider the router one of the most versatile power tools.

Lathe Machine tool which rotates the work piece on its axis

A lathe is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis.

Screwdriver Hand-tool

A screwdriver is a tool, manual or powered, used for driving screws. A typical simple screwdriver has a handle and a shaft, ending in a tip the user puts into the screw head before turning the handle. This form of the screwdriver has been replaced in many workplaces and homes with a more modern and versatile tool, a power drill, as they are quicker, easier, and can also drill holes. The shaft is usually made of tough steel to resist bending or twisting. The tip may be hardened to resist wear, treated with a dark tip coating for improved visual contrast between tip and screw—or ridged or treated for additional 'grip'. Handles are typically wood, metal, or plastic and usually hexagonal, square, or oval in cross-section to improve grip and prevent the tool from rolling when set down. Some manual screwdrivers have interchangeable tips that fit into a socket on the end of the shaft and are held in mechanically or magnetically. These often have a hollow handle that contains various types and sizes of tips, and a reversible ratchet action that allows multiple full turns without repositioning the tip or the user's hand.

Drill Tool used to create holes

A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. with hand-operated types dramatically decreasing in popularity and cordless battery-powered ones proliferating.

Drill bit Cutting tools

Drills are cutting tools used to remove material to create holes, almost always of circular cross-section. Drills come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.

Jackhammer

A jackhammer is a pneumatic or electro-mechanical tool that combines a hammer directly with a chisel. It was invented by William Mcreavy, who then sold the patent to Charles Brady King. Hand-held jackhammers are generally powered by compressed air, but some are also powered by electric motors. Larger jackhammers, such as rig-mounted hammers used on construction machinery, are usually hydraulically powered. These tools are typically used to break up rock, pavement, and concrete.

A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrs. The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press.

Mandrel

A mandrel, mandril, or arbor is a gently tapered cylinder against which material can be forged or shaped, or a flanged or tapered or threaded bar that grips a workpiece to be machined in a lathe. A flanged mandrel is a parallel bar of a specific diameter with an integral flange towards one end, and threaded at the opposite end. Work is gripped between the flange and a nut on the thread. A tapered mandrel has a taper of approximately 0.005 inches per foot and is designed to hold work by being driven into an accurate hole on the work, gripping the work by friction. A threaded mandrel may have a male or female thread, and work which has an identical thread is screwed onto the mandrel.

Collet Type of chuck

A collet is a subtype of chuck that forms a collar around an object to be held and exerts a strong clamping force on the object when it is tightened, usually by means of a tapered outer collar. It may be used to hold a workpiece or a tool.

Chuck (engineering) Clamp used to hold an object with radial symmetry, especially a cylinder

A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In a drill, a mill and a transmission, a chuck holds the rotating tool; in a lathe, it holds the rotating workpiece.

Machine taper

A machine taper is a system for securing cutting tools or toolholders in the spindle of a machine tool or power tool. A male member of conical form fits into the female socket, which has a matching taper of equal angle.

Turning Machining process

Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.

Drill bits are the cutting tools of drilling machines. They can be made in any size to order, but standards organizations have defined sets of sizes that are produced routinely by drill bit manufacturers and stocked by distributors.

Metal lathe

A metal lathe or metalworking lathe is a large class of lathes designed for precisely machining relatively hard materials. They were originally designed to machine metals; however, with the advent of plastics and other materials, and with their inherent versatility, they are used in a wide range of applications, and a broad range of materials. In machining jargon, where the larger context is already understood, they are usually simply called lathes, or else referred to by more-specific subtype names. These rigid machine tools remove material from a rotating workpiece via the movements of various cutting tools, such as tool bits and drill bits.

Boring (manufacturing)

In machining, boring is the process of enlarging a hole that has already been drilled by means of a single-point cutting tool, such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.

Bar stock

Bar stock, also (colloquially) known as blank, slug or billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products. Bar stock is available in a variety of extrusion shapes and lengths. The most common shapes are round, rectangular, square and hexagonal or hex. A bar is characterised by an "enclosed invariant convex cross-section", meaning that pipes, angle stock and objects with varying diameter are not considered bar stock.

Screw Type of fastener characterized by a thread wrapped around a cylinder core

A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in a matching part.

Rotary hammer

A rotary hammer, also called rotary hammer drill is a power tool that can perform heavy-duty tasks such as drilling and chiseling hard materials. It is similar to a hammer drill in that it also pounds the drill bit in and out while it is spinning. However, rotary hammers use a piston mechanism instead of a special clutch. This causes them to deliver a much more powerful hammer blow, making it possible to drill bigger holes much faster. Most rotary hammers have three settings: drill mode, hammer drill or just hammer, so they can act as a mini jackhammer.

Bolt (fastener)

A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed female thread such as a nut. Bolts are very closely related to screws.

A magnetic drilling machine is a portable drilling machine with a magnetic base. It can use twist drill bits, annular cutters, milling cutters, and other rotary cutters. With suitable bits it can also tap threads, ream, and countersink. Its combination of a stable magnetic base and low RPM help resist or reduce torque forces created by large diameter bits. Magnetic drilling machines with reversible motor and variable speed controls can also perform operations like tapping, countersink and reaming. Magnetic drilling machine with cross table base and can also perform light milling.

References

  1. "SDS-plus tool insertion system". Encyclopedia of technical terms (A-Z). Archived from the original on 2007-09-18. Retrieved 2010-04-11.
  2. "SDS". Lexikon der Elektrowerkzeuge. Archived from the original on 2007-08-16. Retrieved 2010-04-11. (German language)
  3. "Standard Dimensions of Sherline Tools". Sherline.com. Sherline Products Inc. Retrieved 30 April 2014.
  4. Judge, Arther W (1947). Engineering Workshop Practice (New and Revised ed.). The Caxton Publishing Company Ltd. pp. Vol i 137.