Thursday, December 8, 2022

What are Morsas or Bench Screws?

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The correct one workpiece clamping Any material that needs to be cut, drilled, filed or machined in any way requires special hand tools to ensure not only high-quality and precise operation, but also maximum comfort and safety for the user.

one of those clamping tools Indispensable in every workshop, whether mechanical, blacksmith, carpentry, plumbing, locksmithing and even watchmaking and the like, are the walruses, also known as bench vices or workshop clamps.

Basically one walrus It is a very robust tool, of variable size, weighing widely between 200 g and 30 kg, and consisting of:

  • A pair of jaws to firmly hold the workpiece preventing any slippage.
  • A spindle or crank manually rotated to open or close the jaws.
  • A support base.

The figure below outlines one of the simplest and most used vise models, with its main parts.

The walrus base mounts to a bench or work table by various methods, depending on the design of the tool, and can be fixed or swivel.

The mouths or jaws there are two: one fixed and another mobile; the moving mouth moves through a axis threaded on a nut housed inside the fixed mouth; at one end, the shaft is provided with a crank. Paths are screwed over mouths jaws interchangeable grooved and of diverse profiles, which are the ones that hold the work piece. By moving the crank clockwise, the jaws close, allowing the clamps to capture the piece interposed between them. If the crank moves in the opposite direction, the jaws open and the jaws release the piece.

The opening of the mouths can occur in two ways, which has given rise to two large groups of walruses:

parallel vise: They are the most used because the jaws always remain parallel in any opening, holding pieces of various sizes in an appropriate way for that size and without the need to exert too much pressure on them. Are walruses They are made of cast iron or cast steel, the latter more expensive but more resistant. Below we will see the parallel vise in detail.

Parallel Vise

Blacksmith or foot vise: They are constructed of forged steel and are very strong. They come from the days when horseshoes were made for horses and are used to support a piece that needs to be hit with a heavy hammer, making them ideal for blacksmithing and forging. They clamp to a sturdy workbench or wall, and the long leg secures to a solid base on the floor. They are not suitable for mechanical adjustment work because their jaws do not stay parallel when opened and therefore parts are not clamped properly or warp if tightened too much.

Types of parallel vise

Due to its more widespread use, parallel vise They present a wide variety of models, and some are even intended for very specific jobs, such as vise for square welding or those used with certain machines, for example, lathes or drilling machines.

In this article we will learn about the most common types of parallel vise.

a) Bench vise

Certainly the kind of walrus used, they are also known in some countries as bench (or bed) vise for machinists. They are used to hold large, heavy objects, and the base bolts securely to a workbench. Depending on the manufacturer, these vises are offered in three models, combined or not. These are:

  • Fixed Base Vise: the most common and economical, available in a wide variety of sizes.
  • Swivel base vise: This base allows the vise to be moved at an angle of 180º for an optimal working position.
  • Vise with anvil: attached to the fixed nose (i.e. to the back) of the tool, the anvil it is useful for light hammering operations to flatten and/or properly shape the part.

The figure below shows examples of these types of bench vise.

Bench vise

b) Table vise

Are bench vise light and portable. They mount to a table or workbench using a clamp located at the bottom. They have knurled jaws to hold the part and some models include a swivel base. They are used to clamp lightweight materials or in areas where sturdier vise are not available.

Table Walruses

c) Clamps for pipes or tubes

They are specially designed to hold round workpieces and are hand-held, portable and extremely robust. They have “V” jaws that allow the piece to be located and locked in position. They are usually mounted on a workbench, although tripod- or shelf-mounted models are also available. They are used to hold 1/8-inch to 8-inch diameter pipe that needs to be cut or threaded.

The vise for pipes They can be of two types:

  • Hinge vise: They are made up of a tilting upper jaw and a fixed lower jaw, both interchangeable and made of hardened cast steel. The fork, the base and the crank are made of cast iron and the screw or shaft is made of steel.
  • Chain vise: They consist of two milled, interchangeable fixed jaws made of cast iron on which the spout rests, which is firmly held by the chain, made of hardened and tempered steel. The base is made of cast iron and the crank is made of cast steel.

Vise for Pipes

d) Flat vise

They are also specially designed to be bolted to a drill press, lathe or workbench. The base can be fixed or swivel, and they come in two sizes: one with 105mm wide jaws and 105mm maximum opening, and the other with 150mm wide jaws and 180mm maximum opening, although these measurements vary. according to the manufacturer. They are used to hold small pieces of wood or metal for machining or drilling operations.

e) Combination vises

As their name indicates, they combine the function of bench vise with vise for pipes or tubes and they can have a fixed or rotating base. They are bolted to a bench or work table and are used to hold heavy objects, pipes for cutting and threading, and for shaping metal.

Combined Vise

Tips for the use and maintenance of walruses

The walruses They are simple machines that do not use electric current and, therefore, their maintenance does not include great requirements.

To carry out the work properly and avoid awkward postures for the operator, it is essential that the vise is mounted at the appropriate height. This height is achieved when the operator is able to touch the top of the walrus jaws with your elbow, as shown in the figure below.

Define posture in the Walrus

Otherwise, the workbench must be raised or a platform must be provided on the floor so that the operator can stand on it.

Machining operations must be carried out in such a way as not to affect the jaws. To do this, the piece mounted on a vise must be held at a suitable height, that is, approximately 1 cm from the jaws. When the vise is not in use, it is recommended to protect the jaws by moving them until they lightly touch and leaving the crank in a vertical position. Never hit a vise with a heavy object or clamp large workpieces in a small vise.

Walruses must be kept well oiled and clean at all times. Chips must not accumulate, especially in the guides through which the mobile mouth, the nut and the shaft move. To this end, they should be cleaned with a cloth after each use and a light coating of oil applied. However, applying oil to the swivel base or swivel joint should be avoided as this decreases the clamping force of the tool.

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