Unlike most turning, milling, and drilling tools, carbide taps have a relatively thin cutting edge and lower overall strength. Even when machining relatively easy-to-cut workpiece materials, the cutting edge of carbide taps is prone to chipping, leading to tool failure. When tapping low-carbon steel, continuous long chips can clog the tap's chip flutes, limiting the application of carbide taps to some workpiece materials that are even easier to tap than steel (such as aluminum and cast iron). Steel and other ferrous materials are the most common materials for machining assembly threaded holes; therefore, tool manufacturers are sparing no effort to develop taps that prevent cutting edge chipping and breakage. Given the inherent performance advantages of carbide compared to high-speed steel, carbide taps have become a development focus.
How can problems encountered during machining be effectively avoided with carbide taps? You need to meet the following requirements!
1. Basic requirements for machine tools
The spindle runout of the machine tool is less than 0.005mm, and the operation is stable.
2. Tool mounting accuracy requirements
After the tap is installed on the tool system, the runout of the machine tool spindle is less than 0.02mm.
3 Requirements for the tool system
Rigid tooling systems should be used, and floating connections should be avoided to prevent tap breakage.
4. Requirements for the threaded pilot hole before tapping
The positional tolerance of the threaded hole to be tapped is less than 0.04 mm, and the chamfer of the hole opening is (0.3～2)×45 degrees, which is approximately proportional to the nominal diameter of the thread.
5. Selection of the geometry of the tap
When machining a through hole, a left-hand spiral flute or a straight flute tap can be selected; when machining a blind hole, a right-hand spiral flute should be selected. When customizing a blind hole tap, the length of the incomplete thread should be provided, and the distance between the front end face of the threaded hole and the front end face of the incomplete thread should be maximized.
6. Requirements for the tool system
Rigid tooling systems should be used, and floating connections should be avoided to prevent tap chipping.
7. Selection of Cutting Fluid
Oil-based cutting fluid is recommended. If this is not possible, water-based cutting fluid (emulsion) can also be used.
8. Selection of cutting speed for carbide taps
A tap without internal cooling and without coating
For tapping gray cast iron threaded holes, the recommended tap cutting speed is v = (20~25) m/min.
For tapping aluminum alloy threaded holes, the recommended tap cutting speed is v = (24~30) m/min.
B-type internal cooling, uncoated tap
For tapping gray cast iron threaded holes, the recommended tap cutting speed is v = (23~29) m/min.
For tapping aluminum alloy threaded holes, the recommended tap cutting speed is v = (28~35) m/min.
C-type internal cooling, coated tap
For tapping gray cast iron threaded holes, the recommended tap cutting speed is v = (30~38) m/min.
For tapping aluminum alloy threaded holes, the recommended tap cutting speed is v = (36~45) m/min.
