A belt sander includes a rotary unit, an oscillating unit, an abrasive belt position detector, a first sensor, a second sensor, and an electric motor control module. The rotary unit includes a retaining seat and an oscillating seat. A lower wheel is pivotally connected to the retaining seat. An upper wheel is pivotally connected to the oscillating seat. An abrasive belt is mounted on the upper wheel and the lower wheel. A recess is formed on the oscillating seat. The oscillating unit includes an electric motor, an eccentric bushing, and a bearing. The bearing is located in the recess. The electric motor drives the upper wheel to oscillate through the eccentric bushing and the bearing, and the abrasive belt is reciprocated left and right. The electric motor is controlled to run or stop running to achieve the function of automatically adjusting the oscillating position of the abrasive belt through the abrasive belt position detector, the first sensor and the second sensor.

A belt sander includes a rotary unit, an oscillating unit, an abrasive belt position detector, a first sensor, a second sensor, and an electric motor control module. The rotary unit includes a retaining seat and an oscillating seat. A lower wheel is pivotally connected to the retaining seat. An upper wheel is pivotally connected to the oscillating seat. An abrasive belt is mounted on the upper wheel and the lower wheel. A recess is formed on the oscillating seat. The oscillating unit includes an electric motor, an eccentric bushing, and a bearing. The bearing is located in the recess. The electric motor drives the upper wheel to oscillate through the eccentric bushing and the bearing, and the abrasive belt is reciprocated left and right. The electric motor is controlled to run or stop running to achieve the function of automatically adjusting the oscillating position of the abrasive belt through the abrasive belt position detector, the first sensor and the second sensor.

Provided is an over-positioning grinding method of a hard and brittle pipe fitting with large length-to-diameter ratio, which belongs to the field of grinding technologies. The existing machining method cannot increase the grinding accuracy of the external circles of the hard and brittle pipe fittings nor ensure the coaxiality of the external circles and internal circles of the ground hard and brittle pipe fittings, which leads to inconsistent wall thickness of the ground hard and brittle pipe fittings. In the present disclosure, by using the over-positioning supporting of the rigid mandrel, the support plate and the guide wheel for the hard and brittle pipe fitting in a machining process, the guide wheel is driven to rotate forward to push the hard and brittle pipe fitting with large length-to-diameter ratio into the grinding area, and the guide wheel contacts and drives the hard and brittle pipe fitting while rotating reversely.

A belt sander includes a rotary unit, an oscillating unit, an abrasive belt position detector, a first sensor, a second sensor, and an electric motor control module. The rotary unit includes a retaining seat and an oscillating seat. A lower wheel is pivotally connected to the retaining seat. An upper wheel is pivotally connected to the oscillating seat. An abrasive belt is mounted on the upper wheel and the lower wheel. A recess is formed on the oscillating seat. The oscillating unit includes an electric motor, an eccentric bushing, and a bearing. The bearing is located in the recess. The electric motor drives the upper wheel to oscillate through the eccentric bushing and the bearing, and the abrasive belt is reciprocated left and right. The electric motor is controlled to run or stop running to achieve the function of automatically adjusting the oscillating position of the abrasive belt through the abrasive belt position detector, the first sensor and the second sensor.

A belt sander includes a rotary unit, an oscillating unit, an abrasive belt position detector, a first sensor, a second sensor, and an electric motor control module. The rotary unit includes a retaining seat and an oscillating seat. A lower wheel is pivotally connected to the retaining seat. An upper wheel is pivotally connected to the oscillating seat. An abrasive belt is mounted on the upper wheel and the lower wheel. A recess is formed on the oscillating seat. The oscillating unit includes an electric motor, an eccentric bushing, and a bearing. The bearing is located in the recess. The electric motor drives the upper wheel to oscillate through the eccentric bushing and the bearing, and the abrasive belt is reciprocated left and right. The electric motor is controlled to run or stop running to achieve the function of automatically adjusting the oscillating position of the abrasive belt through the abrasive belt position detector, the first sensor and the second sensor.