Belt sander motor getting hot, too hot??

C

Creedmoor

Joined
May 7, 2014
Messages
32
Hello,

Hoping some one can answer this question for me.

I have a Kalamazoo 1x42 belt sander that I use for knife sharpening. It has a 1/3hp 110 motor.

It is getting pretty hot during use. Sometimes when I am sharpening it might run for an hour or so. If I put my hand on the motor I can only hold it there for a second or two.

For comparison, I let my old craftsman bench grinder run for a couple hours and it was barely warm.

I called the manufacturer and they didn't seem too concerned but also said that they would exchange it under warranty if I wanted. I don't want to go through all the trouble to send it back if it is normal to get that hot.

What do you think?

Thanks
 
There are a lot of things that can cause an electric motor to get hot. Someone more knowledgeable than me should be along to splain it better, but I will say that I have 6 electrical motor powered devices in my shop right now, and none of them get that hot with similar usage. Some things to think about---are you using the cord the motor came with, plugged straight into the outlet? Is the outlet rated for the current your Kalamazoo draws? Are their any other devices drawing current at the same time you are using your sander? If the answer to the first two are Yes, and the last? is No, then you need a more smarter guy to advise you, my limited experience doesn't like things heating up past the point of not comfortable to touch, including my knife blades!
 
It is the cord that came with it plugged directly into the outlet. Normally nothing else plugged onto the same outlet. Nothing else running in the shop except lights and a small box fan.

Is the outlet rated for the Kalamazoo? I'm not really sure about that or how to verify.
 
Creedmor, I would simply look on the motor of my Kalamazoo, and see what the 'plate' on it said for amperage, and check to make sure that the breaker for that outlet was rated at or above that level. I think you are probably fine, and most household outlets should be fine, BUT.... again some of the guys around here are electrical geniuses and hopefully one of them will see this thread before to long.
 
It's likely that you're simply putting a lot of strain on the machine. 1/3 hp is not much for knifemaking and most of those machines aren't intended to be run for long.

I used a 1/3 HP Craftsman 2x42 for years and that motor housing would get too hot to touch. I was amazed that I never burned that thing up.
 
Thanks for the replies.

Joe, I am just sharpening on it. Very little pressure applied. As a matter of fact, it will get hot just running without being used.
 
The part on the plate where it says rating 40c ambient class B

http://petrowiki.org/Motor_specifications



Insulation classes

The National Electrical Manufacturers Association (NEMA) has established motor-winding-insulation classes to meet motor-temperature requirements found in different operating environments.
The four insulation classes are A, B, F, and H, as illustrated in Fig. 2.

Class-F insulation is most commonly used. Class-A insulation seldom is used. Before a motor is started, its windings are at ambient temperature (the temperature of the surrounding air). NEMA has standardized on an ambient temperature of 40°C within a defined altitude range for all motor classes.

Fig. 2—Motor-winding insulation classes (courtesy of Houston Armature Works Inc.).

Temperature will rise in the motor as soon as the motor is started. Each insulation class has a specific allowable temperature increase.

The combination of ambient temperature and allowed temperature increase equals the maximum winding temperature in the motor.

For example, a motor with Class-F insulation has a maximum temperature increase of 105°C when operated at a 1.0 service factor.

The maximum winding temperature is 145°C (40°C ambient plus 105°C rise).
A margin is allowed to provide for the motor’s "hot spot," a point at the center of the motor’s windings where the temperature is higher.

The operating temperature of a motor is important to efficient operation and long life. Operating a motor above the limits of the insulation class reduces its life expectancy. For example, a 10°C increase in the operating temperature can decrease the motor’s insulation life expectancy as much as 50%.

The motor in Fig. 1 has Class-F insulation and is rated for continuous duty at 40°C ambient.
Click to expand...

145°C is 293°F


800px-Vol3_Page_487_Image_0001.png



It's a good Baldor motor so you can probably trust the specs

Your motor is a class B 80°C rise over the ambient 40°C

120°C = 248°F

More than hot enough to fry bacon and boil tea, but within the specs
 
12345678910 said:
The part on the plate where it says rating 40c ambient class B

http://petrowiki.org/Motor_specifications





145°C is 293°F


800px-Vol3_Page_487_Image_0001.png



It's a good Baldor motor so you can probably trust the specs

Your motor is a class B 80°C rise over the ambient 40°C

120°C = 248°F

More than hot enough to fry bacon and boil tea, but within the specs
Click to expand...

1234567890, Thanks for taking the time to post that.

So according to that info the temperature of the motor is probably within spec. I don't have a way to measure it but I can put my hand on it for a second or two which makes me think it is less than 248 degrees.

My only question remaining is, is it normal for those motors to get that hot? Could there be an issue either with it's construction or my electric supply?

The only reason I am still concerned is that it is still under warranty and Kalamazoo offered to replace it. I would feel bad if I did that and the new one was the same way.

Thanks.
 
My guess is running it for a long time with a "saw duty" motor. Saws aren't meant to run for long times. They are made to deliver lots of power for short times. A compressor duty or a continuous duty motor would be better.
 
I agree with Stacy, the specs and the electrical wiring you said you have make it NOT and issue with current supply or overdraw. I think your motor is OK, but it is just designed for shorter runtimes.
 
I have never seem a motor labeled saw duty. Are there motor that are designed for saw duty and not labelled that way? Is there a way to figure that out from the motor plate? Thanks
 
"SAW DUTY" is new to me, also. Here is what I found:
................The Saw Duty rating, means almost nothing. To be saw duty rated for a certain horsepower, a motor needs to hit that horsepower rating for just a very short time period. An example would be a common table saw used to cut through a 2X4 stud. It does not have to be able to maintain it without overheating or shutting down at all. It just has to hit that horsepower for that second. With these motors it is hard to tell what you are getting. They are usually lower cost, lighter duty motors. They may or may not perform well ..................
 
http://www.fele.com/franklin-aid/just-what-is-a-service-factor.aspx
PT Doc said:
I have never seem a motor labeled saw duty. Are there motor that are designed for saw duty and not labelled that way? Is there a way to figure that out from the motor plate? Thanks
Click to expand...

I had never heard of that term either even though it was on plate. After a couple folks here pointed it out I did some research on it. Mostly negative opinions that I read.

Another term that I read up on is service factor see the link. http://www.fele.com/franklin-aid/just-what-is-a-service-factor.aspx

This motor (if I understand it correctly) has a minimal service factor also.

I did a fair amount of research before purchasing the Kalamazoo and really thought I was getting a pretty good quality piece of equipment to sharpen with.

Hopefully it will last a long time but my expectations have been lowered a bit.

I think that I will try to go easy on it and try turning it off more often instead of leaving it running while examining my work.
 
It probably is a good piece of equipment at the level it is priced at. It just isn't make for heavy and extended run time use.
 
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