The operation method of hand tapping thread is easy to tap after learning

The operation method of hand tapping thread is easy to tap after learning: (1) Draw a line according to the size of the drawing. The problem of marking has been described before, see 'How does a fitter draw a line, it is very simple after learning the method'. (2) According to the nominal diameter of the thread, the bottom hole diameter is calculated according to the relevant formula and then the hole is drilled. 1) Plastic deformation of the material in the process of tapping: In addition to cutting, the cutting edge of the tap also squeezes the material of the workpiece. The extruded material protrudes from the top of the thread profile of the workpiece and is embedded in the tap knife. In the gap at the root of the tooth. At this time, if there is not enough space between the root of the tap cutter and the top end of the thread profile of the workpiece, the tap will be stuck by the extruded material, causing chipping, breaking and rotten threads of the workpiece. Therefore, the diameter of the bottom hole of the thread must be larger than the inner diameter of the thread when tapping. 2) Determination of the size of the diameter of the threaded bottom hole: The diameter of the threaded bottom hole should be considered according to the plasticity of the workpiece material and the amount of expansion during drilling, so that there is enough space to accommodate the extruded material when tapping. The fork can ensure that the processed thread has a complete profile. The method of determining the diameter of the bottom hole drill can be determined by the look-up table method (see relevant manuals). Or use the following empirical formula to calculate. The formula for calculating the diameter of the threaded bottom hole: For steel and ductile metals: the diameter of the threaded bottom hole is approximately equal to the nominal diameter of the thread minus the pitch. For cast iron and brittle metals: the diameter of the threaded bottom hole is equal to the nominal diameter of the thread minus 1.1 times the pitch (3) Workpiece before tapping The clamping position should be correct, and the center line of the screw hole should be positioned in a horizontal position as far as possible. The purpose is to make it easy to judge whether the tap is perpendicular to the surface of the workpiece when tapping. (4) Before tapping the thread, the bottom hole of the screw system should be chamfered, and the holes at both ends of the through-hole threaded bottom hole should be chamfered, which can make the tap easy to cut and prevent the thread of the hole from cracking after tapping. (5) When starting to tap the thread, the tap should be placed as straight as possible, and press the middle of the hinge rod with the palm of your right hand and press the center line of the tap with force. At this time, the left hand cooperates with the screw and keeps the center line of the tap and the center of the hole. The platform should not be skewed. When cutting the workpiece 1 to 2 turns, visual inspection or a square rule can be used to check and correct the position of the tap in two directions perpendicular to each other. When the cutting part completely cuts the workpiece, you should stop applying pressure to the tap, and only need to rotate the hinge screw naturally by the thread of the tap. The attack method is shown in the figure. Figure starting method (6) When the cutting part of the tap has already cut the workpiece, it can only be rotated without pressure, and it should be reversed 1/4 of a turn for each turn, so that the chips can break off, as shown in the figure. When moving the hinge bar, both hands should be evenly balanced. Don't use too much force or shake left and right to prevent the teeth from tearing or the screw holes from expanding. (7) When tapping the thread, it must be tapped to the standard size in the order of joint tap, second tap, and second tap. (8) Precautions: When tapping a thread with a depth requirement on a non-through hole, mark the tap according to the required thread depth to prevent the tapping thread from failing to meet the depth requirement due to chip clogging. It is necessary to withdraw the tap frequently to remove the chips in the hole. When tapping to the bottom of the hole, the chips at the bottom of the hole should be discharged in time to avoid the tap being stuck when tapping to the bottom; when tapping the thread of the through hole, the tap calibration should not be fully tapped, otherwise it will enlarge or damage the last few teeth of the hole Thread; when the tap is withdrawn, the hinge should be used to drive the screw to rotate in the opposite direction. When the tap can be directly rotated by hand, the hinge should be stopped to prevent swing and vibration when the hinge drives the tap to exit, which will damage the thread. In the process of tapping, when changing to another tap, use your hand to hold and screw into the tapped hole until you can’t turn it by hand, then tap the thread with a reamer; When tapping a screw hole with a relatively high material hardness, the head and cones should be tapped alternately, which can reduce the load on the cutting part of the head cone and prevent the tap from breaking; when tapping steel workpieces, adding lubrication to the thread can make the threads clear and can Extend the service life of the tap; for cast iron parts, it can be lubricated with kerosene. In order to reduce the cutting resistance and improve the surface quality of the screw hole, and prolong the service life of the tap; when tapping the thread of a blind hole (not through hole), the tap cannot be tapped to the bottom due to the taper angle in the cutting part of the tap, so that the end cannot be cut completely Thread type, so the depth of the hole should be greater than the thread length, the blind hole depth is calculated according to the following formula, namely the drilling depth u003d the depth of the required screw hole + 0.7 times the major diameter of the thread (ie the nominal diameter of the thread). Previous post: The characteristics of drilling and operation methods and steps, share the skills of grinding drills