Gear hob is a tool for machining spur and helical cylindrical gears according to the meshing principle of helical gears. This tool has high machining precision, high production efficiency and wide application range

Classification of gear hobs

Gear hobs can be classified according to structure, purpose, materials of hob cutting part and number of hob heads.

Gear hobs are divided into integral hobs and inlaid hobs according to their structure.

Gear hobs are divided into rough machining hobs and finish machining hobs according to their uses.

Gear hobs are divided into high-speed steel hobs and cemented carbide hobs according to the materials of hobs.

Gear hobs are divided according to the number of hob heads: single head hobs and multi head hobs.

Key points for selection of gear hob

The accuracy of gear hob has 5 accuracy levels, namely: 3A, 2a, a, B and C; There are also 5 grades of the precision of the processed gear, namely: 6, 7, 8, 9 and 10; The accuracy of hobs before scraping, grinding and shaving is generally class A and class B. Of course, in addition to the accuracy matching, there are some things to pay attention to. Nono has sorted it out for you, as follows:

(1) It is selected according to the accuracy of the machined gear. Integral hob is recommended for gears with grade 7 accuracy and above, and blade hob can be used for others.

(2) It is selected according to the hardness of the machined gear. If the hardness of gear blank is > 300hbw, it is recommended to use blade hob.

• Select according to gear batch and efficiency. If the batch is large and there are high efficiency requirements, the blade hob is used.

Cutting parameters of cemented carbide hob

1. Generally, the cutting speed can be selected within 30 ~ 60m / min;

2. The feed rate can be selected in the range of 1.6 ~ 4mm / R, and the large value can be selected by rough rolling; During fine rolling, in order to reduce the waviness of the machined gear tooth surface, the feed rate should not be greater than 2mm / R;

• Cutting depth. When cutting hard tooth surface gear with carbide hob, because the blunt circle radius of the blade is relatively large, the cutting depth of the first tool shall be larger so that the cutting edge can cut into the gear heat treatment surface. It is necessary to avoid the sliding of the cutting edge of carbide hob on the gear tooth surface, especially when the allowance of the tooth surface is less than 0.05mm. Otherwise, the carbide hob will wear or collapse rapidly. The final finishing cutting depth is limited to 0.1-0.3mm, preferably 0.2-0.25mm.

What are other precautions for carbide hobs?

1. For new or reground carbide hobs, the cutting edge shall be grinded with oilstone before use to round the edge by 0.01 ~ 0.03mm It is known from field experience that the non ground cemented carbide hob has fast blade wear and high machined surface roughness; The milled hob can obtain satisfactory cutting effect, which can not only increase the impact resistance and prevent edge collapse during cutting, but also improve the cutting ability of the tool tip.

2. After the carbide hob is used for 3 ~ 4 times, the blade shape of the rake face shall be checked again on the hob tester. If the tooth shape accuracy is found to be out of tolerance, the tooth shape shall be grinded again.

3. When regrinding the rake face of carbide hob, wet grinding shall be adopted as far as possible, that is, kerosene shall be used as coolant, so as to avoid burns during grinding of rake face and reduce the roughness value of rake face of carbide hob.

Gear hob is a tool for machining spur and helical cylindrical gears according to the meshing principle of helical gears. This tool has high machining precision, high production efficiency and wide application range