Various types and functions of process holes
The shape of the process hole can be round, square or other shapes. Its dimensional tolerance and geometric tolerance can be neither specific nor strict. The process hole may or may not appear in the design drawing of the part. It can remain after processing, or it can disappear after processing. In a word, the process hole has great flexibility, which is reasonable as long as it can be easily processed and assembled without affecting the appearance and normal use of the parts.
Process holes are widely used in machining. The main functions are divided into the following three types. Let's have a look.
It is conducive to ensuring machining accuracy
Some parts have a large number of inclined planes and inclined holes, which makes it difficult to process. Although the positions and inclination angles of these inclined planes and inclined holes are different, they often have one or more central datum points. The processing personnel can find the positions of these datum points, process the process pin holes on these positions, and install the straight pins in the holes, which is of great benefit to the smooth progress of table marking, reverse dimension and inspection.
It should be noted that since the direct pin must have high accuracy, the tolerance of the process pin hole also has strict requirements. In addition, the hole can be punched on the workpiece or on the tooling, which depends on the shape of the workpiece and the specific position of the datum point.
When machining excircles for crankshaft parts, lengthened collets of appropriate length should be reserved at both ends of the total length of the crankshaft, and the process center hole should be punched on the collet according to the position of the center of each excircle, so as to help the lathe or grinder align. Taking the process center hole as the top hole for double apex alignment can play a good role in ensuring the machining accuracy of the excircle.
It should be noted that after each excircle is processed, it must be aligned according to the excircle on the boring machine, and the process center hole on the chuck must be refined until all excircles are finished, and then the chuck can be processed.
Easy to install parts
For some liner parts, there are often very strict requirements for the dimensional tolerance, geometric tolerance and surface roughness in the thickness direction, and grinding machines must be used for finishing. Generally, iron metal parts can be clamped in the form of adsorption, but if they are made of copper, aluminum and other materials, it will be more difficult to clamp.
In this case, some process threaded holes with a diameter slightly smaller than the closing hole can be machined from the position of the closing hole on the drawing, and these threaded holes can be used for clamping. If it is put on the iron tooling, then the iron tooling is adsorbed on the workbench. After finishing the grinding process, expand the process threaded hole into a smooth hole, so that there will be no trace left on the drawing.
Don't despise "small" process holes -- "large" is used as 2.jpg in machining
Improve processing efficiency
Sometimes, working on the workpiece can also remove large processing volume and improve processing efficiency. For example, when processing the jaw frame of the stretching straightener, an enterprise uses the planing method to process the large T-shaped groove of the jaw on the shaper. The length of this large T-shaped groove is large, reaching 1 meter. There is a small groove with a width of 62mm. Due to the low processing efficiency of the planer, it took three days to complete the processing, which seriously slowed down the progress of the project.
After research and improvement, the processing personnel tried to drill a process through hole with a diameter of 40mm at the small groove position to remove the large processing volume in advance. The efficiency of punching is much higher than that of planer planing, so although one process is divided into two, the processing efficiency is greatly improved. After the actual processing test, the efficiency is more than twice that of the original.
In addition, multiple process holes of the same parts can be combined and processed at the same time, which can further improve the processing efficiency. It is a good choice in machining.
