At work we used it to cut glass. Yes, cut glass. A score and a resistance wire heater with a spring. Heat the crack and add a dab of water from a q-tip and break. It was tough cutting glass that was initially 1" x 1"

i wanted to cut a mirror tile around a rectangular heat register. So, I cut maybe a 4" x 3" area of tile. I scored it and then bent a heating element in a L and used the q-tip. Of course it didn't cut the rectangle out, but it tried really hard. I had some glass to nibble, but it worked,

My variac is a weird set-up, but I was may in high school when I did it. I have a 1000 W isolation xformer elsewhere on the bench. Got it for like $10.00 USD. My uncle gave me a 3 A variac which is generally not useful, BUT... I put an analog ammeter and analog voltmeter on it.
The switch I used was a center off. One side would bypass the Variac (Isolation at 15 A) the other side would use the Variac + isolation.

If I did it again, I would add a light or lights that turned on when the switch was on. This is where I would plug in what i was working on. Usually this was an audio amplifier.

Did the Muffin fan speed control at work.

Remeber to fuse the wiper.

Sencore made a nice unit that combined a leakage tester and Wattmeter, Volts and Amps.

Hi,

That's amazing because my uncle gave me a 3 amp variac too when i was still quite young. It took me a while to do something with it though because it was a bare variac, with no power cord or outlet, i had to wire it up myself and place it into a coffee can for the case. Used it a million times after that, but it got stolen somewhere down the line. The one i have now is much bigger though and can handle anything line power oriented (120v 20amp).

 

If i buy it i will use it to slow down the grinder and the drill i have. I want to use the grinder to sharpen knifes etc.I don't like the high speed of the grinder. My grinder and drill do not have variable speed.

Hi,

I would think it would work very well for those, unless the grinder has capacitor start. Some bigger old grinders have cap start. Might still be able to slow it down somewhat anyway though but i never tried that one.

 

Maybe consider phase angle control. It will probably be less expensive and more reliable.

Hi,

Just to note, variacs are very very reliable, and they do not distort the AC sine wave very much like a triac control does.

 

WHAT I DID:

Used to polish the headlight lenses on the cars using a grinder and a buffing wheel. Problem I immediately encountered was burning the plastic. The variac was the solution. Could lower the speed. Governed by the amount of pressure I applied I could fine tune the rate of polishing. The wife asked me if I bought new headlights for her car. "No dear. Those are your old headlights."

At Harbor Freight (don't nobody shoot me please, I know what to expect) I bought a variable speed polisher Only use it to polish the headlights from time to time. She has a newer car now and I haven't had to polish them yet. But the day is coming.

 

At work we used it to cut glass. Yes, cut glass. A score and a resistance wire heater with a spring. Heat the crack and add a dab of water from a q-tip and break. It was tough cutting glass that was initially 1" x 1"

i wanted to cut a mirror tile around a rectangular heat register. So, I cut maybe a 4" x 3" area of tile. I scored it and then bent a heating element in a L and used the q-tip. Of course it didn't cut the rectangle out, but it tried really hard. I had some glass to nibble, but it worked,

My variac is a weird set-up, but I was may in high school when I did it. I have a 1000 W isolation xformer elsewhere on the bench. Got it for like $10.00 USD. My uncle gave me a 3 A variac which is generally not useful, BUT... I put an analog ammeter and analog voltmeter on it.
The switch I used was a center off. One side would bypass the Variac (Isolation at 15 A) the other side would use the Variac + isolation.

If I did it again, I would add a light or lights that turned on when the switch was on. This is where I would plug in what i was working on. Usually this was an audio amplifier.

Did the Muffin fan speed control at work.

Remeber to fuse the wiper.

Sencore made a nice unit that combined a leakage tester and Wattmeter, Volts and Amps.

WHAT I DID:

Used to polish the headlight lenses on the cars using a grinder and a buffing wheel. Problem I immediately encountered was burning the plastic. The variac was the solution. Could lower the speed. Governed by the amount of pressure I applied I could fine tune the rate of polishing. The wife asked me if I bought new headlights for her car. "No dear. Those are your old headlights."

At Harbor Freight (don't nobody shoot me please, I know what to expect) I bought a variable speed polisher Only use it to polish the headlights from time to time. She has a newer car now and I haven't had to polish them yet. But the day is coming.

WHAT I DID:

Used to polish the headlight lenses on the cars using a grinder and a buffing wheel. Problem I immediately encountered was burning the plastic. The variac was the solution. Could lower the speed. Governed by the amount of pressure I applied I could fine tune the rate of polishing. The wife asked me if I bought new headlights for her car. "No dear. Those are your old headlights."

At Harbor Freight (don't nobody shoot me please, I know what to expect) I bought a variable speed polisher Only use it to polish the headlights from time to time. She has a newer car now and I haven't had to polish them yet. But the day is coming.

WHAT I DID:

Used to polish the headlight lenses on the cars using a grinder and a buffing wheel. Problem I immediately encountered was burning the plastic. The variac was the solution. Could lower the speed. Governed by the amount of pressure I applied I could fine tune the rate of polishing. The wife asked me if I bought new headlights for her car. "No dear. Those are your old headlights."

At Harbor Freight (don't nobody shoot me please, I know what to expect) I bought a variable speed polisher Only use it to polish the headlights from time to time. She has a newer car now and I haven't had to polish them yet. But the day is coming.

So that's what i want to use it for. I want it to do experiments in my small electronic lab, but it must be also useful for other things at home, because i don't want to have it, just to have it. I can use with my grinder for sharpening knifes and polish things. I don't like the high speed of the grinder so i want to control it's speed with the Variac. .Besides the grinder i have a small stick welding machine. The control of the welding machine is damaged. I can also control the machine's primary coil with it. I can use it also with my drill, to control the speed. Both the drill and the grinder have universal motors. They do not have a speed control. I also want to use it to control the heat of my soldering iron. Ok, so it's a versatile tool and very useful. I saw one on Amazon, for almost $50 . With shipping to my country it will cost me about $80. It's a 5 amp Variac, which i hope is enough. I think i will go for it.

 

The Variac I have used most for 50 years is 5 amp. Don't know about my others as they are not nearby.

 

Another use I had for mine, I need a slowly increasing 0v-280v DC, I placed a 120v -240v transformer on the output of the Variac and worked great.
Max.

 

So that's what i want to use it for. I want it to do experiments in my small electronic lab, but it must be also useful for other things at home, because i don't want to have it, just to have it. I can use with my grinder for sharpening knifes and polish things. I don't like the high speed of the grinder so i want to control it's speed with the Variac. .Besides the grinder i have a small stick welding machine. The control of the welding machine is damaged. I can also control the machine's primary coil with it. I can use it also with my drill, to control the speed. Both the drill and the grinder have universal motors. They do not have a speed control. I also want to use it to control the heat of my soldering iron. Ok, so it's a versatile tool and very useful. I saw one on Amazon, for almost $50 . With shipping to my country it will cost me about $80. It's a 5 amp Variac, which i hope is enough. I think i will go for it.

Hello,

Make sure you get one that can handle everything you want to use it for.
5 amp wont be enough for some things. I would look for 10 amp minimum. 20 amp can handle anything you can plug into a 120vac receptacle in the United States.
Dont know your location, but if you have 230vac then maybe 5 amp would do it but again check your devices first and what devices you might use in the future too.

Check the wattage of the devices you want to control and get a variac that can handle them or else you'll be sorry later if you get one that is rated too low. It is not good to use a variac for power beyond its rating.

Also make sure the rating you find when buying is a CONTINUOUS rating not a limited time rating like 12 hours or something, unless you plan to use it for 1/2 the rating or for short time periods.

 

Hello,

Make sure you get one that can handle everything you want to use it for.
5 amp wont be enough for some things. I would look for 10 amp minimum. 20 amp can handle anything you can plug into a 120vac receptacle in the United States.
Dont know your location, but if you have 230vac then maybe 5 amp would do it but again check your devices first and what devices you might use in the future too.

Check the wattage of the devices you want to control and get a variac that can handle them or else you'll be sorry later if you get one that is rated too low. It is not good to use a variac for power beyond its rating.

Also make sure the rating you find when buying is a CONTINUOUS rating not a limited time rating like 12 hours or something, unless you plan to use it for 1/2 the rating or for short time periods.

Thank you. You're right. I almost forgot to check the power rating of the devices i want to use it with. The devices i want to use it for are rated above 5 amps. So 5 amp won't do. I will go with the 10 amp version. Thanks again.

 

Hello,

Make sure you get one that can handle everything you want to use it for.
5 amp wont be enough for some things. I would look for 10 amp minimum. 20 amp can handle anything you can plug into a 120vac receptacle in the United States.
Dont know your location, but if you have 230vac then maybe 5 amp would do it but again check your devices first and what devices you might use in the future too.

Check the wattage of the devices you want to control and get a variac that can handle them or else you'll be sorry later if you get one that is rated too low. It is not good to use a variac for power beyond its rating.

Also make sure the rating you find when buying is a CONTINUOUS rating not a limited time rating like 12 hours or something, unless you plan to use it for 1/2 the rating or for short time periods.

The 5 amp Variac i'm interested in won't do, because my devices run on more than 5 amps. The 10 amps Variacs i saw on Amazon are 5 to 6 amp continuous, and also won't meet my needs. I find the 20 amp Variacs a bit expensive. I have a step up/down (120/220 volt) transformer at home. Mains voltage here in Suriname is 120 volts, just like in the USA. I want to use the transformer as a step down transformer. So the output of the transformer will be around 64 Volts. I have ran my devices on the 64 volts and they work well. I like the slow RPM's. What can i buy to make the output of the transformer variable, from 0 to 64 Volts?? I want to use this setup in my small electronics lab too.

 

The 5 amp Variac i'm interested in won't do, because my devices run on more than 5 amps. The 10 amps Variacs i saw on Amazon are 5 to 6 amp continuous, and also won't meet my needs. I find the 20 amp Variacs a bit expensive. I have a step up/down (120/220 volt) transformer at home. Mains voltage here in Suriname is 120 volts, just like in the USA. I want to use the transformer as a step down transformer. I want to connect the 220 side of the transformer to the 120 volt mains. I get around 64 volts at the output on my multimeter. I have ran my devices on the 64 volts and they work well. I like the slow RPM's, especially of the grinder, because it's a dangerous device. What can i buy to make the output of the transformer variable, from 0 to 64 Volts?? I want to use this setup in my small electronics lab too. If there is something to control the output of the transformer i don't have to buy a Variac. I also have the advantage that the secondary coil is isolated.

 

Another use I had for mine, I need a slowly increasing 0v-280v DC, I placed a 120v -240v transformer on the output of the Variac and worked great.
Max.

Check my last reply Max (the one before this one), hope you can help me out.

 

Just saw a rheostat on amazon for $14. Can i control the output of my step up/down transformer with this device. I live in Suriname and mains voltage is 120 volt. I have a 120/220 volt transformer picking up dust. I want to connect mains (120 volt) on the 220 volt side of the transformer and use it as a step down transformer. Output will be 64 volts (checked already with my multimeter.). Can i use the rheostat to control the output from 0 volt to 64 volt.

https://www.amazon.com/gp/product/B..._rd_t=40701&psc=1&refRID=VQSY2ANXX9HXRGC8WZ5Y

 

Understand that when reducing the voltage to a motor to make it run slower means also that it will run weaker. Suppose for a moment you put a polishing disk on your grinder. And for the sake of argument, lets assume you can't burn the plastic. Now, lets also assume you can polish one whole headlight in two minutes at full speed at full voltage. Lets NOW assume you cut the power in half. Half the voltage. You might think it would take you four minutes to polish the same headlight. Wrong. It will take you 8 minutes to do the same job at half the voltage. When you cut power in half you quadruple the time to accomplish the same job. Inverse Square Law. A 1 inch square has 1 square inch surface area. A 2 inch square has 4 square inches of surface area. The 1 inch square is half the size but has 1/4 the area. That's why a 2 minute job at full voltage will take 8 minutes at half the voltage.

 

@Robesim
Be aware that the larger the Variac, the larger its start-up current will be. That "inrush" current can cause problems with similarly rated circuit breakers.

Here are just 2 examples from the Internet:
https://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/variac-question-102710/
https://hackaday.com/2016/05/15/taming-a-variac-with-a-thermistor/

The Hackaday link gives one solution.

John

 

Understand that when reducing the voltage to a motor to make it run slower means also that it will run weaker. Suppose for a moment you put a polishing disk on your grinder. And for the sake of argument, lets assume you can't burn the plastic. Now, lets also assume you can polish one whole headlight in two minutes at full speed at full voltage. Lets NOW assume you cut the power in half. Half the voltage. You might think it would take you four minutes to polish the same headlight. Wrong. It will take you 8 minutes to do the same job at half the voltage. When you cut power in half you quadruple the time to accomplish the same job. Inverse Square Law. A 1 inch square has 1 square inch surface area. A 2 inch square has 4 square inches of surface area. The 1 inch square is half the size but has 1/4 the area. That's why a 2 minute job at full voltage will take 8 minutes at half the voltage.

Check my last posts/replies. Instead of a Variac, can i use a transformer with a Rheostat.?

 

Check my last posts/replies.

Yes. I understood that. Just pointing out the power factor. Half the voltage doesn't mean twice the time to do the same job. 's all I'm saying.

 

@Robesim
Be aware that the larger the Variac, the larger its start-up current will be. That "inrush" current can cause problems with similarly rated circuit breakers.

Here are just 2 examples from the Internet:
https://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/variac-question-102710/
https://hackaday.com/2016/05/15/taming-a-variac-with-a-thermistor/

The Hackaday link gives one solution.

John

Hi,

Just watch the extreme temperature rise of the inrush current limiter device, which can get above 200 degrees C at full current.

 

Check my last posts/replies. Instead of a Variac, can i use a transformer with a Rheostat.?

Hi,

Without seeing the rheostat i would say it 's not going to work very well. That is because a rheostat works by dropping voltage and thus it dissipates a LOT of power and gets hot. You if yo uuse it to run a fan, you might also be running a heater at the same time because it might get hot and heat up the area too.

Not sure what your shipping costs are to your area, but you can look elsewhere for a variac. Circuit Specialists have better prices on variacs for example.

 

@Robesim
Be aware that the larger the Variac, the larger its start-up current will be. That "inrush" current can cause problems with similarly rated circuit breakers.

Here are just 2 examples from the Internet:
https://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/variac-question-102710/
https://hackaday.com/2016/05/15/taming-a-variac-with-a-thermistor/

The Hackaday link gives one solution.

John

Check my last posts/replies. Instead of a Variac, can i use a transformer with a Rheostat.?

Hi,

Without seeing the rheostat i would say it 's not going to work very well. That is because a rheostat works by dropping voltage and thus it dissipates a LOT of power and gets hot. You if yo uuse it to run a fan, you might also be running a heater at the same time because it might get hot and heat up the area too.

Not sure what your shipping costs are to your area, but you can look elsewhere for a variac. Circuit Specialists have better prices on variacs for example.

This is the Rheostat. Can i use it to control the output of a step down transformer??
https://www.amazon.com/gp/product/B..._rd_t=40701&psc=1&refRID=VQSY2ANXX9HXRGC8WZ5Y