tweezers

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Tweezers are tools used for picking up small objects that are not easily handled with the human hands. They are probably derived from tongs, pincers, or scissors-like pliers used to grab or hold hot objects from the dawn of recorded history.

Tweezers make use of two third-class levers connected at one fixed end (the fulcrum point of each lever), with the pincers at the others.

Tweezers have many uses, such as gold panning, in the manual construction or repair of many things such as models, clockwork, surface mount electronics; or in cosmetics for plucking eyebrows.

History

Two sticks would be used to pinch another stick over a stone age fire. Tweezers are known to have been used in predynastic Egypt. There are drawings of Egyptian craftsmen holding hot pots over ovens with a double-bow shaped tool. Asiatic tweezers, consisting of two strips of metal brazed together were common to Mesopotamia and India about 3000 B.C. These likely served purposes such as catching lice.^[1] There is evidence of Roman shipbuilders pulling nails out of construction with plier-type pincers.

It is widely recognized in most industries that rely on tweezers that the first precision tweezers were made in 1875 by a self-taught watchmaker, in La Sagne, Switzerland. With just a hammer, anvil and files, he was able to construct tools (tweezers) which put in valuable service in the exacting field of watch timing.

As different varieties of tweezers were invented, this Swiss watchmaker assigned style numbers to those tools. It’s significant to note that the majority of precision tweezers made today carry that very same numbering, regardless of the manufacturer or country of origin. It’s also interesting to note that the founders of several of the more well-known European manufacturers of tweezers today once worked for the company this watchmaker founded.

In the late 19th century most tweezers were made from carbon tool steel because it was readily available and easy to work. Once the grinding and filing was done the tips of the tweezers were flame hardened for strength. These carbon steel tweezers were coated with a light oil to prevent oxidation.

In the 20th century as these precision tweezers found their way into medical applications, there was a need for precision tweezers that were less apt to oxidize. AISI 440 Stainless Steel became a staple material for the manufacture of medical tweezers. The tweezer manufacturers simply added an ‘S’ to the style number to signify that the tweezer was made of Stainless Steel.

In the 1950’s, the birth of the electronic industry spurred the need for a material that had less magnetism. Precision tweezers began popping up made of AISI 303/304 and AISI 316 Stainless Steel. These alloys while softer than AISI 440 Stainless Steel, were much less magnetic and more suited to electronic assembly. The suffix ‘SA’ was used for these alloys, which stands for Stainless Anti-Magnetic and for many years it was considered a standard not only in the electronic industry, but also in the medical field.

Types

Flat tip conventional tweezers.

Tweezers come in a variety of tip shapes, including pointed, blunt and tapered. There are also various types of specialised forms of tweezers, including:

• Optical tweezers use light to manipulate microscopic objects as small as a single atom. The radiation pressure from a focused laser beam is able to trap small particles. In the biological sciences, these instruments have been used to apply forces in the pico Newton range and to measure displacements in the nm range of objects ranging in size from 10 nm to over 100 mm.

• Magnetic tweezers use magnetic forces to manipulate single molecules (such as DNA) via paramagnetic interactions. In practice it is an array of magnetic traps designed for manipulating individual biomolecules and measuring the ultra-small forces that affect their behavior.

Plastic tweezers used in first aid kit

• Electric tweezers deliver an electrical signal through the tip, intended to damage hair roots and prevent new hair from growing from the same root.

• Vacuum Tweezers use differences in atmospheric pressure to grasp items as small as 100 micrometres to parts weighing several pounds. Special vacuum tweezer tips are manufactured to handle a wide variety of items such as surface mount electronics, optics, biological material, stamps or coins. Uses include assembly or handling of items where contamination by finger oils must be avoided or for parts that are so small that conventional mechanical tweezers may cause loss or damage of parts.

• Molecular tweezers are noncyclic host molecules that have two arms capable of binding guests molecules through non-covalent bonding.

• Stamp tweezers or Stamp tongs are specially designed tweezers used for handling postage stamps.

• Hot tweezers are designed to grip small surface-mount electronic devices, while simultaneously heating them for soldering or desoldering.

References