Coating of taps
1, steam oxidation: tap into the high temperature water vapor, the surface of the formation of an oxide film, the coolant adsorption is good, can play a role in reducing friction, while preventing the tap and the cutting material between the bond, suitable for processing mild steel.
2, nitriding treatment: tap surface nitriding, forming a surface hardening layer, suitable for processing cast iron, cast aluminum and other material on the tool wear.
3, steam + nitriding: comprehensive advantages of the above two.
4, TiN: golden yellow coating, good coating hardness and lubricity, and coating adhesion performance is good, suitable for processing most materials.
5, TiCN: blue gray coating, hardness of about 3000HV, heat resistance of 400°C.
6, TiN+TiCN: dark yellow coating, with excellent coating hardness and lubricity, suitable for processing most of the materials.
7, TiAlN: blue gray coating, hardness 3300HV, heat resistance up to 900°C, can be used for high-speed processing.
8, CrN: silver gray coating, lubrication performance is superior, mainly used for processing non-ferrous metals.
The coating of the tap has a significant impact on the performance of the tap, but at present, the manufacturers and coating manufacturers cooperate with each other to study the special coating, such as LMT IQ, Walther THL, etc.
Factors that affect tapping
A. Tapping equipment
1. Machine tool: it can be divided into vertical and horizontal processing methods. For tapping, vertical is better than horizontal processing, and horizontal processing should consider whether cooling is sufficient.
2, tapping shank: tapping is recommended to use special tapping shank, machine rigidity, good stability is preferred to choose synchronous tapping shank, on the contrary, as far as possible to choose flexible tapping shank with axial/radial compensation. Use square drive whenever possible, except for small diameter taps (<m8).< span=""></m8).<>
3. Cooling conditions: for tapping, especially extrusion taps, the requirement for coolant is lubrication > cooling; In actual use, it can be prepared according to the conditions of the machine tool (when using emulsion, it is recommended that the concentration is greater than 10%).
B. The workpiece to be processed
1. The material and hardness of the processed workpiece: the hardness of the workpiece material should be uniform. It is usually not recommended to use taps to process the workpiece more than HRC42.
2, tapping bottom hole: bottom hole structure, choose the right bit; Bottom hole dimensional accuracy; Bottom hole wall mass.
C. Processing parameters
1, speed: speed is given on the basis of the type of tap, material, processed material and hardness, the advantages and disadvantages of tapping equipment.
Usually selected according to the parameters given by the tap manufacturer, the speed must be reduced under the following conditions:
▶ machine tool rigidity is poor; Large tap beating; Inadequate cooling;
▶ Tapping area material or hardness is not uniform, such as solder joints;
▶ The tap is lengthened, or an extension rod is used;
▶ Supine, outside cold;
▶ Manual operation, such as bench drill, rocker drill, etc.;
2, feed: rigid tapping, feed =1 pitch/turn.
Flexible tapping, and the shank compensation variable is sufficient:
Feed = (0.95-0.98) pitch/revolution.
Some tips on tap selection
A. Tolerances of taps of different precision grades
Selection basis: not only according to the precision grade of the thread to be machined to select and determine the precision grade of the tap
▶ The material and hardness of the processed workpiece;
▶ Tapping equipment (such as machine conditions, clamping handle, cooling ring, etc.);
▶ The tap itself accuracy and manufacturing error.
For example: processing 6H thread, in steel processing, can choose 6H precision tap; In the process of gray cast iron, because the middle diameter of the tap wear faster, the expansion of the screw hole is small, so it is appropriate to choose 6HX precision tap, the life will be better.
Note on the accuracy of Japanese taps:
▶ Cutting tap OSG uses OH precision system. Different from ISO standard, OH precision system forces the whole tolerance band width from the lowest limit, every 0.02mm as a precision level, named OH1, OH2, OH3, etc.
▶ Extrusion tap OSG uses RH precision system, RH precision system will force the whole tolerance width from the lowest limit, every 0.0127mm as a precision level, named RH1, RH2, RH3 and so on.
Therefore, when replacing OH precision tap with ISO precision tap, 6H should not be considered as approximately equal to OH3 or OH4 level. It should be determined by conversion or according to the actual situation of the customer.
B. Outer dimension of the tap
1. At present, the most widely used are DIN, ANSI, ISO, JIS, etc.
2, according to the customer's different processing requirements or existing conditions to choose the appropriate length, blade length and handle square size
3. Interference during processing;
Tap selection of six basic elements
1, the type of processing thread, metric, British, American, etc.;
2. Type of thread bottom hole, through hole or blind hole;
3, processed workpiece material and hardness;
4, the workpiece complete thread depth and bottom hole depth;
5, workpiece thread precision;
6, the appearance of the tap standard (special requirements need to be marked).
Post time: Sep-22-2022