Hello everyone, today we are going to try to remove a little more myth and mystery about vintage sewing machine motors. When I first started talking about motors my intention was to focus on the misconception that vintage all steel domestic (household) sewing machines can be used in the same category of sewing as their industrial/commercial counterparts. Simply not true, there are many limiting factors that separate the two distinctive classes of machines. Motors are only one of them.
sewing machine motor mysteries
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Refresher About Sewing Machine Motors
In the first part of this series, our discussion turned away from the power of the motors. Instead focused on the various types of sewing machine motors and defined the description of each type. This was important because there are so many different types ranging from easy-to-find to impossible-to-replace motors.
Most externally mounted motors are going to be relatively easy to find replacements for. Belt drive systems are easier than friction drives simply because there are more of them. Remember a friction drive motor turns in the opposite direction of the hand wheel while a belt drive motor turns in the same direction as the hand wheel. Gear drive systems follow the same laws of physics as a friction drive. To my knowledge, they are going to be an OEM motor so replacements can be limited and scarce.
In the later years of the all-steel vintage sewing machine, manufacturers started adding a cover that enclosed the externally mounted motor. This eventually morphed into fully enclosed motors and proprietary mounting on the inside of the machine bodies. During this time of metamorphosis, these same manufacturers discovered plastic. From this point forward the long-term reliability was traded off for the lighter, quieter, easier to handle, cheaper disposable commodities.
Brush Type Motors
Vintage sewing machine motors are brush-type motors that by design can be operated either on AC current or with DC current. These motors allow for variable speeds simply by using a variable resistor to reduce the voltage being applied to the motor. This reduction of voltage through a resistor slows down the motor rpm for slower speeds. The downfall of this is it also cuts the motor power ratio down. The resistors will build a lot of heat as it slows the voltage down resulting in a foot pedal for the sewing machine getting hot when slow sewing is required over a longer period of time.
Typical household sewing machines use motors rated in tenths of an amp, with a shaft speed of 3000 rpm. Keeping this as simple as possible it is the amount of power the motor is designed to use for the work it is designed to manage. Too much work on the motor and the amps will go above the rating. The shaft speed will slow down at full power and the motor will burn up.
Smallest Sewing Machine Motor
The smallest rated sewing machine motor I have personally seen to date is rated at .4 amps. These are found on very basic machines usually only straight stitch. As the functions of the machines increase so does the amount of work the motor needs to do and the motors will reflect this by being rated with higher amp ratings. So more work means stronger motors are needed. The higher the amps, the stronger the motor.
Typical Household Sewing Machine Motors
The majority of household machines will use motors between .7 and 1.0 amps. Vintage sewing machines that have built-in decorative stitches or use a fashion disc or cam as it is commonly called will typically use motors rated at 1.0 amp up to 1.5 amps with some of the 1.2-1.5 amp motors turning a shaft speed of 5000 rpm. These motors may also utilize a dual rating system in which they show not only amps but also HP (horsepower). A 1.2 amp motor at 5000rpm shaft speed will probably be rated at an equivalent of 1/20hp whereas a 1.5 amp motor equates to a 1/15hp.
All this being said not all sewing machine motors will utilize these types of rating systems. Some manufacturers of machines in different countries or motors intended to be shipped worldwide will use a rating system based on the amount of energy absorbed into the work being performed. Much like a standard light bulb, these motors are rated in watts. With the same results as a light bulb, the more light emitted the higher the watt rating, which translates to the more work created for the motor to do the higher the wattage must be to do it.
Ok well, I hope I haven’t totally confused everyone yet. Sometimes I think I confuse myself and I know the end of the story. We touched upon the 3 basic motor rating systems and how they each relate to the raw power that contributed to the strength of the sewing machine. Motors alone do not make the machine strong. So next time we will explain a little about needle speed and gear ratio. Until next time enjoy your machines, and may your grandkids never cut cardboard with your shears.