What is the difference between collar and shoulder?
1. Shaft shoulder is the structure on the shaft; The collar is a separate ring part.
2. The annular surface formed at the change of the shaft diameter of the shaft shoulder is the shaft shoulder, which is generally used for positioning the parts on the shaft; The collar can be sleeved onto the shaft and has the same function as the shoulder.
3. The use of shaft collar is due to the fact that the direct use of shaft shoulder requires large diameter raw materials, which is less economical.
Shaft shoulder and collar are the most reliable positioning methods for shaft parts. They are all structures on the shaft and belong to a part of the shaft, rather than being removable like a shaft sleeve.
Role of shoulder
1. Increase the fastness of interference fit
Generally, the interference fit is used for the fit of plastic gear and shaft, and the interference amount is not more than 0.2mm. If the machining accuracy is not high, it is easy to slip. In order to increase the fit fastness between the gear and the shaft, the shoulder is often punched at the fit, but the shoulder should not be too large to prevent the plastic gear from cracking. When cylindrical gear and double gear are fitted with shaft, the dimension of shaft shoulder is: D=d+(0.04~0.10) mm. For worm and single gear with a long mating surface with the shaft, the size of the shaft shoulder is: D=d+(0.15~0.20) mm.
2. Axial positioning
A retaining ring or collar equivalent to a mechanical part. When the axial force in the gearbox is small or the parts are not subject to axial force, in order to avoid large friction between the parts on the shaft and the gearbox wall during operation, the shaft shoulder can be used as the shoulder for axial positioning. The size of the retaining shoulder is larger than that of the mating shoulder, so D=d+(0.3~0.4) mm.
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