Parallel blocks
.the types of parallels
.the constructional features of parallel blockd
. uses of parallel blocks
The parallel blocks of different types are used for setting workpieces for machining. The commonly used are of two types.
Solid parallels
Adjustable parallel
Solid parallels
This is the type of parallel which is very much used in machine shop work. They are made of steel pieces of rectangular cross secction and are available in different lengths and cross sectional sizes.
They are hardened and ground and, sometimes, finished by lapping.
Paralles are machined to close limits, and are perfectly flat squre, and parallel throughout the length. These are made in pairs of indentical diemensions.
Grades
Parallels are made in two grades-Grade A and Grade B. Grade A is meant for fine toolroom type of work, and Grade B for general machine shop work.
Adjustable parallels
These consist of two tapered blocks sliding one over the other in a tongue and groove assembly. These types of parallels can be adjusted and set to different heights.
Uses
Solid and adjustable parallels are used for parallel setting of workpieces while machining. They are also useful for raising the workpieces held in vices or machine tables to provided better observation of the machining process.
Parallels are made in pairs and should be used in matching pairs to ensure accuracy in set up sizes of parallels
Designation of parallels
Parallels are designated by the type, grade (for solid parallels only)size, and the number of the standard.
Examples
Solid parallel A5 ×10×100 IS:4241
Adjustable parallel 10×13 IS:4241
Range and size of adjustable parallels
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