Precision Parallel Sets

What Are Precision Parallel Sets?

Precision parallel sets are rectangular steel boxes that are used to raise the workpiece off the table when machining with a milling or drilling machine or other machine tools. The main goals of the precision parallel sets are to prevent the cutting tools from hitting or damaging the table or equipment and to ensure smooth, precision, and safe operations when cutting through the metal works.

Precision parallel sets come in pairs of spacers that are typically made from tool steel, stainless steel, and cast iron. The parallels are usually critically ground in different heights and also thickness in some cases. A wide range of heights of tops and bottoms of the precision parallel sets permit the machinists to bring the workpieces above the tops of the vise jaws in order to complete different precision machining tasks. As the name implies, during the machining production, the parallels maintain the workpieces parallel to the surface of the table where the parts need to be clamped in a vise or other fixtures. For instance, raising a work evenly in a milling machine vise and provide a perfect height for the spindle to pass through. 

When it comes to the style of the precision parallel sets, the metal spacers are produced with different levels of tolerance, a wide variety of heights, and sizes. Many precision parallels are hardened to keep the accessories from wearing over time or prevent them from being unparalleled. However, in some cases, softer, not hardened spacers are used in machining tasks to prevent damage to end mills, drill bits, or other cutting tools since most cutting tools can significantly wear or break due to the hardened steel. Thicker precision parallel sets are usually utilized for large and heavy parts while thinner ones are ideal for narrow parts and clamping devices.


Faces of Precision Parallels

As mentioned, precision parallel sets typically come in a pair of the top portion and a bottom portion, which are produced and ground to have the same dimensions. The various choices of thickness and size make the precision parallel sets greatly versatile since they can be stacked up or applied to irregular parts that do not have flat contours.

In general, precision parallels have four faces that are critically produced, including the front, the back, and two sides, however, there may be faces that do not have smooth surfaces. On the front face, there are a series of drilled holes, which are used for installing the workpieces or clamping devices. There are also countersink on the sides to eliminate the sharp edges. If these faces are machined by a grounding process, then the parallel sets will have surfaces with grain. On the other hand, the faces will have a smooth and mirrored finish if they are lapped. Ideal surface tolerance and surface finish permit a temporary molecular attraction.


Manufacturing of Precision Parallel Sets

The steel parallels come in two basic levels in relation to surface tolerance in the market, which is the tighter and lower surface tolerance type. Having tighter surface tolerance, the precision parallel sets are more suited for inspection tasks and high precision manufacturing machining operations. The latter can be used for metalwork applications that require relatively lower accuracy.

In precision parallel sets production, the steel parallels are produced to rough dimensions first and leave several millimeters for further grinding. The steel parallels will be paired and fed to the grinding machine, subsequently, the faces of parallel sets can be accurately ground to achieve the demand dimensions. To meet the operational specifications, some customized finishes are applied in order to eliminate all the burrs as well as sharp edges, by milling, typically. When sold in sets, the precision parallels are produced to either metric or imperial sizes in heights and thickness.


How Do Precision Parallel Sets Work?

In milling, turning and many more machining operations, precision parallel sets are widely used to support the metal parts being cut when they are placed in the machine vises or clamped to the bed of the machine tools. Whenever the metal parts are too small or thin to be in contact with the 3 faces of the machine vise when cutting, the steel parallels can be helpful, using either side to provide clearance from the vise and support underneath the metal parts. 

The precision parallel sets can remove the risks that the workpieces will be pressed down when the forces of the cutting tools applied to them. With the precision parallel sets, the vise, as well as the workpieces, can be secured, preventing the drill bits or other cutting tools to damage the vise or protecting the parts if the vises themselves have damaged contacting faces.

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