Gun drill

Gun Drill

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Gun drill

Gun drills are straight fluted drills which allow coolant

Cutting fluid

Cutting fluids are various fluids that are used in machining to cool and lubricate the cutting tool. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, and mists....
(either compressed air or a suitable liquid) to be directed through the drill's body, directly to the cutting face.

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Encyclopedia

Gun drills are straight fluted drills which allow coolant

Cutting fluid

Gun barrel

A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases is released in order to propel a projectile out of the end at great speed....
s are the obvious example. Other uses include the manufacture of woodwind instruments, such as uilleann pipes

Uilleann pipes

The uilleann pipes , originally known as the Union pipes, are the characteristic national bagpipe of Ireland. The uilleann pipes bag is inflated by means of a small set of bellows strapped around the waist and the right arm....
, as gun-drills are capable of drilling long straight holes in metal, wood and some plastics. The coolant provides lubrication and cooling to the cutting edges as well as ejecting the swarf

Swarf

Swarf are shavings and chippings of metal?the debris or waste resulting from metalworking operations. It can usually be recycling, and this is the preferred method of disposal due to the environmentalism regarding potential contamination with cutting fluid or tramp oil....
or chips back out the drills length. Modern gun drills take advantage of carbide

Tungsten carbide

Tungsten carbide, WC, or tungsten semicarbide, W2C, is a chemical compound containing tungsten and carbon, similar to titanium carbide....
tips

Tool bit

The term tool bit generally refers to a non-rotary cutting tool used in Lathe , shapers, and Planer . Such cutters are also often referred to by the set-phrase name of single-point cutting tool....
to reduce expense and prolong life. The images show the coolant holes in the drills shank and tip, as well as full length (12 mm dia × 635 mm long) gun drill and the carbide tip of a second (25 mm) gun drill.

Motivation

It is difficult to drill a deep hole (where deep is approximately 3 times the diameter of the hole) that is both straight and accurately sized with a standard twist drill. This is a problem in many manufacturing processes, especially the firearms industry. The barrel of a gun must be very straight and quite accurately sized. Gun barrels are far longer than their inside diameter; as an example, the .223 inch (5.56 mm) barrel of the M-16

M16 rifle

M16 is the Military of the United States designation for a family of rifles derived from the ArmaLite AR-15 and further developed by Colt's Manufacturing Company starting in the mid-20th century....
rifle is 20 inches (508 mm) long, nearly 90 times the diameter. Thus the gun drill was invented to create these long straight holes.

Construction

There are two basic types of gun drills: the internal chip removal type and the external chip removal type. The internal type is basically a tube with a cutting bit on the front. Coolant is forced around the outside of the tube, and pours around the front of the drill forcing the chips into the center of the tube, and out of the hole.

The external chip removal type operates similarly except there is a notch cut in the outside of the drill, through which the chips exit, and a passage for the coolant goes through the center of the bar. The drill bit, however, is highly susceptible to breakage during drilling operations.

External links

on rifle barrel drilling