More likely you'll fry the variac.
AC motor speed is determined by the frequency of the line, not the voltage.
Save the variac for a different project.

You should be able to use it to control things with universal motors (AC motors with brushes) like many hand tools, vacuum cleaners etc. If you adapt a vacuum motor to your bandsaw you could do it. The motors usually employed for bandsaws and other stationary tools are not of this type and will usually run hot at lowered voltages. Be careful with devices that are allready variable speed, conflict between controlers can be destructive. Make sure the variac has the capacity to run whatever you are trying to control. A friend had one of these in front of his soldering iron, variable wattage, worked great.
Bill

I don't know but I would think you would burn out the motor. They are designed to operate on a specific voltage. Increasing or decreasing the voltage beyond normal tolerances is not a good idea. Case in point, the warnings on extension cords to be sure to use a large enough or short enough cord to avoid voltage drop that can cause damage.
I would think that you would need to replace your motor with one designed for variable voltage in order to get variable speeds. And of course the Variac needs to have a capacity that meets the motor's power needs.

Chet Guilford

About 20 years ago I built an 18" bandsaw from a Gilliom Company's kit and experimented with electronic speed reducers on it for a couple of years so that I could saw not only wood but also steel. A motor rebuilder friend in S. California sold me a 1/2 hp dc motor equipped with a variable speed controller. This motor-controller combination didn't have the power I needed to cut steel. Therefore, I exchanged it for a 3/4 hp ac motor with an ac variable speed controller (this type was later discontinued by Emerson, the manufacturer) from him. It did not work too well at the low speeds necessary for sawing steel because the motors hunting for its set speed caused a slight jerkiness in the motion of the bandsaw's blade. This made for erratic cutting of metal, and, an occasional binding of the blade. My friend suggested that he could build for me a speed controller that could be used with the high-speed, universal motor from a vacuum cleaner but I chose not to try that route.

Nowadays, there are two types of electronic speed controllers in use: dc controllers used with dc motors and ac frequency controllers used with three-phase ac motors. I believe that the ac frequency controllers can also be used with single-phase ac motors - but am not entirely sure of this. I have a 1 hp dc motor and dc speed controller powering my large belt grinder. It produces a wide range of belt speeds that allows me to grind steel on the high-speed end as well as plastics on the low-speed end (without melting or burning them). My grinder still has a noticeable loss of hp when using the low speed end. I haven't tried using an ac variable frequency controller but have heard that it works very well. These ac controllers tend to be high-priced however. I gave up trying to convert my 18" bandsaw to a variable-speed one after purchasing and rebuilding a used 20" wood and metal cutting bandsaw. This saw uses the old fashioned but tried and true method of speed control: a two-speed gearbox in combination with a variable-pitch pulley drive to achieve a wide range of speeds - from 50 to 4,500 fpm blade speed. The disadvantage of this kind of drive is its bulkiness and complexity of gears. A pin sheared or slipped in it a while back and I've only got the low speeds available. I've got to take it apart again and fix it but don't look forward to a day or two of dirty work.

Thanks for all the great info., folks... I think I'll add the Variac to my ever-growing pile of looking-for-a-good-use stuff.

Cheers,
Chris

49DegreesNorth, what Dee mentioned is an excellent suggestion for a relatively inexpensive way to convert your bandsaw to a variable-speed one. It will take your devising a way to mount a "Jack shaft," a second shaft with pulleys, at the base of your bandsaw. If you contact me offline, I can dig up some information for you (from my literature file) on the appropriate pulley ratios and some methods of how others have done this.