1x30 belt sander (not what you think)

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Gradyw

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Jan 23, 2017
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Hey everyone I'm trying to figure out how I can control the speed on my cheap harbor freight belt sander. Not really control it but slow it down a good bit. I know I've seen at least one YouTube video where a guy made something where he could control how much power was going in to the machine but I can't remember where I seen that or what it was called... if anyone knows what I'm talking about a name for it would be a really good start. I would love if I could get my belt sander to run at like half the speed or maybe even less and I'm sure a lot of other people would too.
 
I'm guessing what you're looking for is a variable frequency drive or variable feed drive, or a single phase vfd.
 
Variable frequency drive won't work because the motor needs to be three phase.. I know somebody that got a fan control switch from home Depot and it works on his.. I think you have to start on full speed then dial it back .
 
Topshot said:
Variable frequency drive won't work because the motor needs to be three phase.. I know somebody that got a fan control switch from home Depot and it works on his.. I think you have to start on full speed then dial it back .
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Did you just say it wouldn't work because it needs to be three phase but it worked for your buddies?
 
Kootaga13 said:
Did you just say it wouldn't work because it needs to be three phase but it worked for your buddies?
Click to expand...
No, he said a vfd will not work with a single phase induction motor. He said he knows of someone who uses a fan control switch, which only reduces voltage, works for them.

The problem is the hf motor is designed to run at a certain voltage, frequency, and speed. It's windings are designed for a certain full load amperage. When you reduce the voltage, and not the frequency, the amperage (current) goes up, which produces more heat. Variable speed fan motors are wound with heavier wire to take the excessive heat produced by lowering the voltage and increasing the amperage, the hf motor is not. The hf motor will eventually overheat for a long enough period to cook the insulation, break it down, and short the windings.

The other problems besides burning up the motor with excessive heat from current draw, is reduced cooling from the fan, and reduced torque at lower speeds than designed.

There's more to it than the above, like understanding electricity in general, inductance, capacitance, eddy currents, etc...but that's it in a nutshell.
 
Thanks brother, I was having a who's on first moment.

While I have you here and you seem quite knowledgeable, if you put two, 100 feet extension cords on that 1x30, would it slow in down but harm the motor?
 
In addition to the length of the run, it depends on the voltage supplied, current draw of the motor, and size of the wire.
With too small a wire size, you will have excessive voltage drop, which will damage the motor.
 
I've thought about taking s real cheap cord with a double plug in and using it to run something that takes a lot of power to try to slow it down that way.. that would work I just don't know how good. It would be a pain in the ass too haha
 
That type of motor will lose torque if run slowly, and will overheat.

You would be better off mounting the drive wheel to a shaft bearing and reducing speed with some step pulleys or better yet get a DC motor with variable speed control. It WILL cost more than the grinder, but you'll still have the motor and it can be used for future projects.

cbwx34 linked to this in another thread.
https://www.pennstateind.com/store/TCLVSKIT.html

Some reviews complain it doesn't have enough HP for higher torque turning projects (lathe) but on the HF 1x30 it should work fine. Shaft diameter might even work out of the box and just drill some holes/add some standoffs to match the mounting configuration. Is a good price for a complete solution.

I use a similar modified HF 1x30 and it is extremely handy. Belts are cheap, good selection, I've used it to do regrinds and for setting bevels. With the OEM motor I won't use it for sharpening.
 
Gradyw said:
I've thought about taking s real cheap cord with a double plug in and using it to run something that takes a lot of power to try to slow it down that way.. that would work I just don't know how good. It would be a pain in the ass too haha
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That's how electrical fires get started. The real 'pain in the a$$' would be something like your house burning down as the end result of using the cheap, under-rated cord. The motor will still try to draw it's rated current load regardless, and the cheap cord will eventually overheat and fail. It usually happens at the plug ends, at the mechanical connection between the wire's conductors and the blades of the plug; that connection is inherently the most resistive in the circuit (most prone to generating heat with current flow), and therefore the weakest link in the cord as a whole. That's where too much heat will melt the cable jacketing and/or the plug housing itself, exposing hot, bare, electrified wiring.

It's sort of analogous to trying to pump water at high pressure and high volume through a too-small garden hose that's not rated for the pressure or the flow rate. Something's gotta give, and that'll be the hose.

This is the whole reason for the warning labels on electrical equipment and cords used to power them, in warning users not to use extension cords below a certain rated amperage for a given tool. Some will also include warnings not to 'daisy chain' extension cords together for a longer cable run. If doing so, the rated amperage size of the cable must also be increased, to prevent overheating issues. This is why extension cords get thicker and heavier the longer they are, as the conductor size must be heavier to maintain a given amperage rating at a given length of cable run.


David
 
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Gradyw said:
I've thought about taking s real cheap cord with a double plug in and using it to run something that takes a lot of power to try to slow it down that way.. that would work I just don't know how good. It would be a pain in the ass too haha
Click to expand...

It would be the same end result as what jpm2 wrote in his post (good post btw).

I think most here start on the HF sander... but at some point you realize there's better options. For me it was the Viel (around 80 bucks)... put a 1725 rpm motor on it (which runs around 1350 rpm with the wheel size on the Viel)... and eventually a variable speed motor I found (but not necessary). Getting the Viel was totally worth it... not only for the slower speed, but it also ran a lot smoother. (I didn't realize how "rough" the HF ran until then).

Sounds to me like you're there.... I think it's totally worth it for a better setup, if it's something you plan on using a lot.
 
Please let me add that I'm not stupid enough to run a motor or even a 20" box fan with 200' of extension cord. It was the theory of the idea I was questioning. Let alone the fire hazard, wouldn't it shorten the life of the motor if not kill it.
 
Thanks cbxw34, that's just what I recall off the top of my head.
New things might have been discovered that affects voltage drop, but this is the formula we used, back in the day.

single phase
VD=(2 x D x I x K)/CM

3 phase
VD=(1.73 x D x I x K)/CM

VD/supplied voltage gives %VD.

Where
VD= volts dropped
2= number of current carrying wires in the run, typical for single phase circuits (hot & neutral).
1.73= conversion factor for number of wires in a 3 phase circuit because of shared load.
D= distance of run, measured in feet
I= total load of the circuit in amperes. For a motor it should be the name plate FLA (full load amps) at 100%.
K= resistance constant? = 12.9 for copper or 21.2 for aluminum.
CM= circular mills of the wire, found here.
http://www.engineeringtoolbox.com/awg-wire-gauge-circular-mils-d_819.html
I think the circular mills of a given size wire can be slightly different depending on how many strands it has. The above link might only be for solid wire. Best to look up the exact wire.

There is another factor involved to compensate for self inductance, but only applies to size 2/0 wire and above.

Note: Stranded wire has more current carrying capacity than the same size (awg) solid wire, but not sure what, if any affect it has on voltage drop.
 
As for varying the speed of a single phase motor, a lot of this has already been said, but here's my thoughts.

I'm not aware of any reliable and practical way to electrically do it with type of motor on hf belt sander.
I think those motors use capacitors to shift the phasing and create rotation. There's generally a start capacitor, to get the motor going, then a run capacitor, which is brought into the circuit via mechanical centrifugal switch. I think this creates a problem to try and electrically vary the speed.
The only vfd's I've dealt with are for 3 phase motors, each phase I think is 120 degrees from each other. This creates rotation without the need for capacitors, easy for drives to deal with.
I think fan motors have "shaded poles". Not sure exactly what they are or how they work, but do the same thing as the capacitors. These shaded poles, along with the heavier windings allow varied speed with voltage only.

Again even if you did find a way to do it without electrically damaging the motor, you'd still have the issue with torque and cooling air flow.

IMO the best way with a single phase is mechanically, through gearing, shivs, belts, pulleys, etc.
 
Maybe the safest and most cost effective method would be to get some inexpensive blades and practice enough to get comfortable with the sander at its recommend speeds.
 
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