As a common tool for processing internal threads, the tap can be divided into spiral groove tap, edge dip tap, straight groove tap and pipe thread tap according to the shape, and can be divided into hand tap and machine tap according to the operating environment, and can be divided into metric tap, American tap and British tap according to specifications. Taps are also the main processing tools used in tapping.
Today I share with you a tap selection guide to help you choose the right tap.
Classification of taps:
1. Cutting taps
- Straight slot tap: used for processing through hole and blind hole. Iron filings are found in tap slots, and the thread quality is not high. It is more commonly used for processing short chips, such as gray cast iron, etc.
- Spiral groove tap: used for blind hole processing with hole depth less than or equal to 3D. Iron scrap is discharged along the spiral groove, and the thread surface quality is high. 10~20° spiral Angle tap can be processed with thread depth less than or equal to 2D; The 28~40° helical Angle tap can process the thread depth less than or equal to 3D; The 50° spiral Angle tap can be used to process the thread depth less than or equal to 3.5D (4D under special working conditions).
In some cases (hard materials, large tooth pitch, etc.), in order to obtain better tip strength, spiral groove taps will be used to process through holes.
- Screw tip tap: usually only used for through hole, aspect ratio up to 3D~3.5D, iron chip down discharge, cutting torque is small, the threaded surface quality is high, also known as edge dip tap or tip tap. When cutting, it is necessary to ensure that all cutting parts are penetrated, otherwise there will be tooth collapse.
- Extrusion taps
It can be used for processing through hole and blind hole, forming tooth shape through plastic deformation of material, and can only be used for processing plastic material.
Its main features:
1, using the plastic deformation of the workpiece to process the thread;
2, the cross-sectional area of the tap is large, high strength, not easy to break;
3, the cutting speed is higher than the cutting tap, and the productivity is also improved accordingly;
4, due to the cold extrusion processing, the mechanical properties of the thread surface after processing are improved, the surface roughness is high, the thread strength, wear resistance, corrosion resistance is improved;
5, no chip processing.
The disadvantages are:
1, can only be used for processing plastic materials;
2. High manufacturing cost.
There are two structural forms:
1, no oil groove extrusion tap is only used for blind hole vertical addition;
2, with oil groove extrusion tap is suitable for all working conditions, but usually small diameter taps due to the difficulty of manufacturing do not design oil groove.
Structural parameters of taps：
1. Shape and size
- Total length: attention should be paid to some special lengthening conditions
- Slot length: on
- Handle: At present, the common standard of handle is DIN(371/374/376), ANSI, JIS,ISO, etc. When selecting the handle, attention should be paid to the matching relationship with the tapping tool handle.
2. Threaded part
- Precision: selected by specific thread standards, metric thread ISO1/3 grade is equivalent to national standard H1/2/3 grade, but need to pay attention to the manufacturer’s internal control standards.
- Cutting cone: The cutting part of a tap that has formed a partially fixed pattern. Generally, the longer the cutting cone, the better the life of the tap.
-Correction teeth: play the role of auxiliary and correction, especially in the tapping system is not stable working conditions, the more correction teeth, the greater the tapping resistance.
3. chip groove
- Groove type: affects the forming and discharge of iron filings, usually for each manufacturer’s internal secrets.
- Front Angle and rear Angle: when increasing, the tap becomes sharp, which can significantly reduce the cutting resistance, but the strength and stability of tooth tip decrease, and the rear Angle is the rear Angle of shovel grinding.
- Number of slots: increasing the number of slots increases the number of cutting edges, which can effectively improve the tap life; But will compress the chip removal space, in the chip removal disadvantage.
The material of the tap:
1. Tool steel: mostly used for hand incisor taps, which are not common at present.
2. High speed steel without cobalt: At present, it is widely used as tap material, such as M2(W6Mo5Cr4V2,6542), M3, etc., the mark code is HSS.
3. Cobalt-containing high speed steel: at present, a large range of tap materials, such as M35, M42, etc., mark code for HSS-E.
4. Powder metallurgy high speed steel: used as a high performance tap material, the performance is significantly improved compared with the above two, each manufacturer’s naming method is different, the mark code is HSS-E-PM.
5. Hard alloy materials: usually choose ultrafine particles, good toughness grade, mainly used for manufacturing straight slot tap processing short chip materials, such as gray cast iron, high silicon aluminum, etc.
The tap is highly dependent on the material. The selection of good materials can further optimize the structural parameters of the tap, so that it is suitable for high efficiency, more demanding working conditions, and at the same time, it has a longer life. At present, large tap manufacturers have their own material factories or material formulas. At the same time, due to the problems of cobalt resources and prices, new high-performance high speed steel without cobalt has also come out.
Coating of tap:
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:
1 Tapping equipment
- Machine tool: can be divided into vertical and horizontal processing methods, for tapping, vertical is better than horizontal processing, horizontal processing to consider whether the cooling is sufficient.
- Tapping handle: it is recommended to use a special tapping handle. If the machine tool is rigid and stable, synchronous tapping handle is preferred, instead, flexible tapping handle with axial/radial compensation should be used as far as possible. Use square drive whenever possible, except for small diameter taps (<m8).< span=”"></m8).<>
- 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%).
2 Workpiece to be processed
- Workpiece material and hardness: workpiece material hardness should be uniform, it is generally not recommended to use taps to work over HRC42.
- Tapping bottom hole: bottom hole structure, choose the right bit; Bottom hole dimensional accuracy; Bottom hole wall mass
3 The processing parameters
3.1 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:
- Poor rigidity of machine tool; Large tap beating; Inadequate cooling;
- Uneven material or hardness of the tapping area, such as solder joints;
- taps are lengthened or an extension rod is used;
- Lying, outside cold;
- Manual operation, such as bench drill, rocker drill, etc
3.2 Feed: rigid tapping, feed =1 pitch/turn. Flexible tapping and handle compensation variable is sufficient: feed = (0.95-0.98) pitch/revolution.
Some tips on tap selection:
-Tolerance 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 shank, cooling environment, etc.);
-The accuracy and manufacturing error of the tap itself.
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.
- Size of tap outer shape
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, edge 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).
Welcome to your enquiry at any time!
Lillian Wang
Giant Tools Only the best tools we made
Tianjin Ruixin Tools & Hardware Co., Ltd.
Email: wjj88@hbruixin.net
Whatsapp:+86-18202510745
Phone/Wechat: +86-18633457086
Web:www.giant-tools.com
Post time: Nov-10-2022