Skills and precautions of traditional manual tapping;
First, the steps and skills of manual tapping
The quality of manual tapping is greatly influenced by human factors, and the tapping strength is low because of the small diameter of threaded hole. Therefore, only by adopting the correct method can the quality of the workpiece tapped by fasteners be guaranteed.
(1) Clamping of workpiece
Generally speaking, when clamping a workpiece, the side of the workpiece that needs tapping 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 positioning of the faucet
At the beginning of tapping, straighten the faucet, then straighten the faucet with one hand and gently turn the hinge lever with the other hand. Observe whether the tap is perpendicular to the base surface of the workpiece from the front or side, and correct it with a square ruler if necessary, and the direction of the tap will be basically determined.
(3) Calibration of the faucet
If the position of the tap is not correct at the beginning of tapping, it can be corrected by screwing out the tap with two cones and tapping the thread with the head cone. When all the cutting parts of the tap enter the workpiece, there is no need to apply axial force, and the thread naturally screws in.
(4) the stability of the faucet
The force should be even. When rotating the hinge lever, the operator should balance the strength of his hands to avoid overexertion and shaking from side to side. Otherwise, it is easy to tear the thread profile, which will cause the thread hole to become larger and thinner, and the tap will be broken.
(5) the outlet of the faucet
Turn the tap back with the hinge rod after the tap is loose, because the tap hole is loosely matched with the tap. Avoid shaking and vibration of the tap when exiting, thus destroying the surface roughness of the thread.
Second, the treatment method of tap fracture
The factors affecting the quality of machine tool taps include: main material, NC tool design, heat treatment, machining accuracy, coating quality, etc. For example, the size difference at the transition of the tap section is too large or the transition fillet is not designed, which leads to stress concentration and is easy to break at the stress concentration when used.
(1) Technological factors of faucet
When the tap is heat-treated, it may be cracked if it is not preheated before quenching, overheated or overheated after quenching, backfired in time and cleaned too early.
(2) Selection factors of faucet
High quality machine tool taps, such as cobalt-containing high-speed steel taps, cemented carbide taps, coated taps, etc. For tapping parts with too high hardness, you should choose. The number, size and angle of tap chip removal grooves have an influence on chip removal performance.
(3) Material factors of the workpiece
With the emergence of new workpiece raw materials, there are more and more varieties of tool materials, which requires the selection of suitable taps before tapping. When the material of the percussion piece is impure and there are hard spots or air holes in some parts, the percussion will suddenly lose balance and break.
(4) Performance factors of machine tools
Machine tools and clamping mechanisms are also important, especially high-quality taps. Only a certain precision machine tool and clamping mechanism can play the role of tap. When tapping, that is, the spindle axis is not concentric with the center line of the bottom hole, and the torque is too large during tapping, which is the main reason for the fracture of the tap.
Three. Selection of special tapping oil
Special tapping oil is the lubricating medium that must be used in the thread cutting process of fasteners. High-precision thread cutting requires high cooling, lubrication, penetration and cleaning performance of tapping oil. When using waste engine oil and vegetable oil instead of special tapping oil, it is easy to have burrs and other bad situations, and the tap life will be greatly reduced.
(1) High-efficiency tapping oil has excellent lubrication performance, low friction coefficient and high extreme pressure.
(2) The special tapping oil has strong adhesion and firm oil film, which can effectively protect the tap and improve the thread quality.
(3) Good cooling performance can effectively restrain the temperature rise, reduce the occurrence of sintering and seizure, and has special effects in reducing edge collapse and broken tap.
(4) The special tapping oil is used to remove chips more smoothly, and a large amount of iron chips will be produced during tapping, which is easy to stick to threaded holes and taps. At this time, the iron filings must be washed off with special tapping oil.
(5) Because the non-corrosive vulcanizing auxiliary agent is used as the main agent, the special tapping oil has no peculiar smell and does not irritate the skin, which can effectively avoid the problems such as skin allergy of workers.