1. Tapered Button Bits with furnace test block:
Carburize and quench the test block with the charge; when the load is left on the frame, immediately break the test rod and check the depth of the crack penetration layer. Generally, the permeable layer can be determined by visual inspection of cracks. In addition, a 2-5% nitric acid alcohol solution is used to etch the fracture surface, so that the fracture surface can be inspected more accurately, and the carburized layer can be determined.
Through the inspection of the test block in the furnace, it can be ensured that the batch of carburized parts reaches the specified carburized layer; the workpiece is processed according to its design requirements.

2. Special test block of taper button drill bit:
This test block is equipped with a specific workpiece according to its technological requirements for measuring the depth of the infiltration layer. They are usually made of steel with the same furnace number as the workpiece. When carburizing, as close to the workpiece as possible. The size and shape of the test block should not be consistent with the furnace test block; it mainly depends on the shape of the test materials provided, such as rods, heads, etc. After carburizing, the inspection content is exactly the same as the test block with furnace.
3. Carbon gradient test block of taper button drill bit:
There are generally two methods for measuring the carbon content gradient: one is the chemical analysis method of delamination of iron filings; the carbon content analysis of the spectrometer.

Fourth, taper button bit quality spot check test block:
When carburizing a large number of smaller workpieces, one part can be randomly selected from each batch for damage inspection. This can be a spot check form specified by the user; it can also be an internal quality check method. The contents and required items of the spot check by the taper button drill manufacturer may include the following:
1. Hardness inspection of the entire cross-section, with emphasis on hardness measurement near the surface.
2. Metallographic examination, including evaluation of microstructure, grain size and smoothness.
3. Tensile test and impact test are mostly micro test bars.
4. Grain rheology caused by forging or stamping.
5. Measure the residual stress through the surface layer.