Tap and die

However they still fit tighter than actual fasteners, and are fluted like regular taps and dies so debris can escape.

Car mechanics, for example, use chasers on spark plug threads, to remove corrosion and carbon build-up.

While modern nuts and bolts are routinely made of metal, this was not the case in earlier ages, when woodworking tools were employed to fashion very large wooden bolts and nuts for use in winches, windmills, watermills, and flour mills of the Middle Ages; the ease of cutting and replacing wooden parts was balanced by the need to resist large amounts of torque, and bear up against ever heavier loads of weight.

As the loads grew even heavier, bigger and stronger bolts were needed to resist breakage.

Thus builders of, for example, locomotives, firearms, or textile machinery were likely to make their own taps and dies.

During the 19th century the machining industries evolved greatly, and the practice of buying taps and dies from suppliers specializing in them gradually supplanted most such in-house work.

[1] With the introduction of more advanced milling practice in the 1860s and 1870s, tasks such as cutting a tap's flutes with a hand file became a thing of the past.

In the early 20th century, thread-grinding practice went through significant evolution, further advancing the state of the art (and applied science) of cutting screw threads, including those of taps and dies.

GTD was so vital to the Allied war effort from 1940–1945 that anti-aircraft guns were placed around its campus in anticipation of possible Axis air attack[citation needed].

The correct hole diameter is listed on a drill and tap size chart, a standard reference in many machine shops.

With soft or average hardness materials, such as plastic, aluminum or mild steel, common practice is to use an intermediate (plug) tap to cut the threads.

The machinist must frequently eject chips to avoid jamming or breaking the tap.

With hard materials, the machinist may start with a taper tap, whose less severe diameter transition reduces the torque required to cut threads.

The operator must get this alignment close to ideal to produce good threads and not break the tap.

A comprehensive reference for US tap and drill bit sizes can be found in the chart provided by Albany County Fasteners.

These have a tip that is split through the flutes and an axial screw which forces the cutting edges slightly apart.

This chamfer helps center the die on the blank and reduces the force required to start the thread cutting.

Manufacturers of dies have produced models in a hex form which are intended for the creation of new threads.