Taps are tools used to create various medium and small internal threads. They have a simple design and are easy to use. They can be operated manually or on machine tools, which makes them widely used in production.
Struggling to play during the processing process? Don't worry! Today, I'll share some tips to help you gain a deeper understanding of touch.
What's playing ?
Tapping is the process of cutting an internal thread inside a hole in a workpiece using a tap.
1) Factors that determine male performance include:
Workpiece material, cutting speed, cutting edge material, tool holder, tap shape, hole size, threading tool holder, cutting fluid and hole depth.
2) Argument:
The axial distance between two adjacent teeth on a thread corresponds to two points on the pitch diameter line.
The life of a tap can be significantly extended with each additional cutting tooth on the tap. Tests have shown that tool life can be doubled for each half of the cutting tooth thread.
Unlike other tools, the chip load of a tap can only be changed by the number of chip removal grooves and the length of the cutting tap.
3) Inverted tap:
Similar to all the other tools, the tap is also slightly inverted.
4) Screw the blade back
The advantages of using a screw paddle include less heat build-up in the tap and less plastic build-up on the back of the workpiece, which can help mitigate chip build-up in the screw.
Disadvantages of using a rear-screw blade include the cutting edge becoming brittle and prone to collapse, insufficient rigidity of the main shaft and fixture (including a floating tool handle), and the possibility of small chips becoming embedded during rotation reverse, leading to collapse of the cutting edge.
5) Touch Tolerance
Each tap has its own unique pitch diameter.
Taps marked with H or D tolerance (mainly American taps) indicate the thread size of the tap through the H/D tolerance. The letter indicates whether the tap size is larger than (H = imperial, D = Metric) or smaller than (L = imperial, DU = Metric) the basic pitch diameter. The actual core size is expressed relative to the basic pitch diameter, such as H2, D3, L1, or DU2.
Taps are also often marked with a thread grade. For example, a general series of HP taps indicates that the tap is the correct size for the fit class of the part. A grade 3B tap is suitable for a grade 2B part, and a tap marked with a grade “X” indicates that it has a large tolerance and is used for precision taps, galvanized or heat-treated parts, or materials with close elasticity. memory.
For galvanized male threads, it is necessary to select a tap with a higher degree of tolerance for internal threads. A larger pitch diameter will result in a slightly larger thread size, and increasing after electroplating will bring the thread size back to the specified value.
Tap cutting treatment
1) Hole type and chip handling
2) Extrusion cutting, chip removal spiral tap:
Spiral chip removal tap is more suitable for blind hole and deep hole processing. It is recommended to use materials that produce sticky chips, making it ideal for intermittent cutting.
The tapered core of the spiral chip removal tap is very thin, making it the most vulnerable part of the tap design. To avoid breakage, the speed must be 30% to 40% lower compared to a straight tap for chip removal.
3) Remove the cut
4) Straight tap for chip removal:
For materials that tend to break chips, such as brass, cast iron or hardened steel, it is recommended to use a high-strength tap. Coolant or gas is usually required to remove chips from the chip removal groove.
Faucets can come in a variety of cut shapes, including:
- Taper (Shape A) “A” – initial touch
- Plug (Forms B and D) “B/D” – middle tap
- (Form C) “C” – semi-flat bottom or modified flat bottom
- (Form E) “E” – flat bottom
5) Extrusion tap:
Its processing characteristic is that there is no chip in the through hole or blind hole.
6) Comparison between cutting core and extrusion core
7) Influence of the size of the bottom hole on the extrusion screw
Faucet coating
1) Advantages of the coating
① Surface Treatment: Improves the appearance of HSS cores without changing their size.
② Longer tap life: Provides high wear resistance, reduces friction and energy consumption, reduces blade collapse and breakage, and slightly increases surface hardness.
③ Improves surface quality and dimensional accuracy of screw holes: maintains a sharp cutting edge with lubricating effect, reduces load and scratches, and minimizes chip accumulation.
2) What is a tumor chip?
The workpiece material is welded or bitten into the edge of the chip.
At the beginning of cutting, an accumulation of chips forms and grows throughout the cutting process.
When chip accumulation becomes severe, cutting pressure causes chips to break and fragments to become embedded in the workpiece, leading to poor finishing and deviations from the desired size.
When the chip buildup fragments, the tool material particles break apart, leading to tool wear.
3) Traditional surface treatment
Oxidation treatment:
2) Chip winding
- Change ringtone
→ straight groove
→ smaller helix angle
- Shorten shut-off tap
- Change the shape of the front corner
- Increase the number of vacancies
- Change speed
- Smaller hook
- In case of rigid threading, increase the pecking cycle
- Consider extrusion faucet
3) Lubrication selection
The purpose of lubrication in threading is to reduce friction.
Therefore, threading lubricants rather than coolants are generally used.
If liquid refrigerant is used, add EP (ultra-high pressure) or HP (high pressure) additives.
The tap has a large, fixed feed rate that is controlled by the tap pitch, while the drilling feed can be adjusted to control the load.
4) Application of coolant
Tap the selection base
Before selecting a faucet, we need to understand:
- Hole type, through hole, blind hole or deep hole
- Minimum drilling depth
- Minimum thread depth required
- Are extrusion taps considered?
- Material of the part to be machined
