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How to tap the thread by hand and precautions?

Update:02-12-2021
Summary:

At present, hand tapping threads still occupies a certa […]

At present, hand tapping threads still occupies a certain position in machinery, because in actual production, some threaded holes are not suitable for machine tapping threads due to the limitation of the location or the shape of the parts. Because the diameter of the threaded hole is small, the strength of the tap is low, and it is easy to break the tap with machine tapping. Generally, hand tapping is often used. However, the quality of hand tapped threads is greatly affected by human factors, so we can only guarantee the processing quality of hand tapped threads by adopting the correct method of tapping.

(1) The clamping of the workpiece must be correct for the clamping of the processed workpiece. Under normal circumstances, the side of the workpiece that needs to be tapped should be placed in a horizontal or vertical position. It is convenient to judge and keep the tap perpendicular to the base surface of the workpiece.

(2) The initial position of the tap is when starting to tap the thread, the tap should be placed straight, and then the tap should be straightened with one hand, and the hinge rod should be gently rotated with the other hand. Observe whether the tap is perpendicular to the base surface of the workpiece from the front or side, and use a square ruler to correct it if necessary.

(3) If the thread is not correct at the beginning, you can unscrew the tap and use a double cone to correct it, and then tap the thread with the head taper. When the cutting part of the tap enters the workpiece, it is no longer necessary to apply axial force. Just screw in.

(4) When manually tapping fine threads or threads with higher precision requirements, the feed amount should be appropriately reduced each time; the speed of tapping cast iron can be appropriately faster than that of tapping steel; when tapping deeper threads, for convenience Chip breaking and chip removal, reduce the phenomenon of chip sticking on the cutting edge, ensure a sharp edge, and at the same time enable the tapping oil to smoothly enter the cutting part, which plays a role of cooling and lubrication.

(5) When using force to rotate the hinge rod evenly, the operator's two hands must be balanced, avoid excessive force and shaking left and right, otherwise it is easy to tear the thread profile and cause the threaded hole to expand and appear taper.

(6) When tapping the blind hole thread with the exit tap operation method, when the end tap is finished tapping, after the reamer is used to reverse the tap to loosen, it is almost necessary to unscrew the tap, because the threaded hole and the tap have a loose fit. The hinge rod is heavy. If the hinge rod is used to unscrew the tap, it is easy to produce swings and vibrations, thereby destroying the surface roughness of the thread. When tapping through-hole threads, try not to make the calibration part of the tap all over, so as not to enlarge or damage a few threads.

(7) Application of group taps When using group taps to tap the thread, after the head tap is finished, the two or three tapers should be screwed into the threaded hole by hand. Operation to prevent random buckling caused by misalignment of the thread tapped by the previous tap.
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