The manufacturing unit of a machine is a part, which is connected to form a machine by certain means. A thread connection is one of the ways to connect parts. Therefore, the thread is often one of the most common structures on parts. For a sheet metal processing factory, the most common thread tapping is internal thread tapping, especially in the chassis, instruments, communication chassis, audio case and other industries, but the details of tapping quality and power, cost and so on are often neglected by sheet metal processing plants.
Common Processing Method of Internal Thread
1) Tapping threads by machine tappers
In the practice of mass production, the first choice is to select machine tapping threads with good quality, high power, and low production cost.
A. The radial runout of the spindle of the drilling machine should be generally adjusted within 0.05 mm.
B. Thread tapping operation method When the tap is about to finish threading, the feeding tool should be light and slow to prevent interference and impact between the front end of the tap and the bottom hole depth of the sheet metal workpiece threads and damage the tap; when tapping blind hole threads or deep threads, thread tapping safety chucks should be used to accept the cutting force.
C. The selection of cutting speed for tapping threads depends primarily on cutting data, taper diameter, pitch and depth of threaded holes. Generally, when the depth of the threaded hole is within 10-30 mm and the workpiece is as follows: steel v = 6-15 m/min, tempered steel or harder steel v = 5-10 m/min, stainless steel v = 2-7 m/min, cast iron v = 8-10 m/min, under the same conditions, the diameter of the tap is relatively high, and the diameter of the tap is large. For low speed, the pitch should be large and low speed.
D. When choosing the cutting fluid for tapping threads, the cutting fluid is mainly selected according to the sheet metal processing data, and the cutting fluid to be satisfied must be adhered to. For the metal data, the emulsifier is generally selected; for the plastic data, the emulsified oil or vulcanized cutting oil is generally selected. If the surface roughness of threaded holes on the workpiece is low, rapeseed oil and molybdenum disulfide can be used, and the effect of soybean oil is better.
2) Hand tapping method and matters needing attention
When tapping threads, it is generally advisable to rotate 1/2-1 at a time. However, under special circumstances, specific problems should be specifically analyzed, such as the tap under M5 should not be more than 1/2 turn at a time; when tapping fine teeth threads or threads with high precision requirements, the feed per time should be appropriately reduced; tapping cast iron can be appropriately faster than tapping steel, after each spin, the reverse is about 1/2 turn. When tapping deeper threads, to facilitate chip breaking and chip removal, reduce the phenomenon of cutting edge stickiness, ensure sharp edges, together with cutting fluid smoothly into the cutting position, play a cooling and smooth effect. Also, when tapping blind hole threads, the tap should always be withdrawn and the chips should be removed to ensure the effective length of the threaded hole.