Plectropomus
4th May 2021, 11:48 AM
Hi brains trust,
I have an issue with heating of the motor case on my bench grinder.
I inherited a Makita GB800 8inch bench grinder that had never been used. For a variety of reasons, it stayed unused for 20 years, in storage inside the box in a variety of humid and hot conditions in the tropics.
Now I finally have a workshop I have begun using it and noticed the casing was very hot to the touch.
Tonight I ran it for (timed) 20 minutes with no workload at all, and at the end of this time I could leave my right index finger on it for 6 seconds. I could leave my left index finger on it for just 2 seconds. I am right handed, so perhaps my right finger is "work hardened" :)
The heat is definitely emanating from the centre of the machine -- not the end bearings. The wheels spin freely and there is no noise of any remark. There is some vibration, and it may be because I have not "trued" the wheels. I believe both wheels came with the machine.
There are holes under the casing for aeration of the motor cavity, and plastic fans are visible inside. I am concerned that humidity during storage may have affected the electrical components somehow.
My questions are: (1) Should I be concerned, (2) is this "normal"?, and (3) what could I test using a multimeter for faults?
The Googling I have done provides contradictory information -- some say a 20 minute run under no load should be "cool to the touch", and others say it could be quite hot to touch, as the motors are designed to operate at high temperatures. I have no infrared temperature gauge and live in a rural area, so I have no accurate information on the ambient temperature or the temperature of the casing.
Can you advise?
:C
Cheers, Mike
I have an issue with heating of the motor case on my bench grinder.
I inherited a Makita GB800 8inch bench grinder that had never been used. For a variety of reasons, it stayed unused for 20 years, in storage inside the box in a variety of humid and hot conditions in the tropics.
Now I finally have a workshop I have begun using it and noticed the casing was very hot to the touch.
Tonight I ran it for (timed) 20 minutes with no workload at all, and at the end of this time I could leave my right index finger on it for 6 seconds. I could leave my left index finger on it for just 2 seconds. I am right handed, so perhaps my right finger is "work hardened" :)
The heat is definitely emanating from the centre of the machine -- not the end bearings. The wheels spin freely and there is no noise of any remark. There is some vibration, and it may be because I have not "trued" the wheels. I believe both wheels came with the machine.
There are holes under the casing for aeration of the motor cavity, and plastic fans are visible inside. I am concerned that humidity during storage may have affected the electrical components somehow.
My questions are: (1) Should I be concerned, (2) is this "normal"?, and (3) what could I test using a multimeter for faults?
The Googling I have done provides contradictory information -- some say a 20 minute run under no load should be "cool to the touch", and others say it could be quite hot to touch, as the motors are designed to operate at high temperatures. I have no infrared temperature gauge and live in a rural area, so I have no accurate information on the ambient temperature or the temperature of the casing.
Can you advise?
:C
Cheers, Mike