Headstock, DC Motor, and Speed Control Assembly (2800 RPM)
Product #: 3306
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Sherline utilizes the same power head combination on all lathes and mills. This headstock features a spindle that rides in large 20 mm bearings at each end with an adjustable preload nut located behind the pulley. The spindle nose has a 3/4-16 external thread and #1 Morse internal taper. The through hole is .405 (10mm) in diameter. The powerful DC motor offers its maximum torque at low RPM where you need it most in machining. This means it offers far more useable power than an AC/DC motor of equivalent or larger size. It also offers smoother and quieter operation than an AC/DC motor. When running the spindle at the higher speeds made possible by the pulley set used on the 3307, the cutting tools are usually very small in size, so a lot of torque is not required. Although the second pulley position lowers the speed range down to that of the standard headstock, the motor provides so much torque that most users find they can leave the pulleys set in the high speed position even when doing more demanding milling jobs with larger cutting tools and lower speeds.
To power and control the motor a more sophisticated speed control unit is required. This unit accepts any incoming AC current from 100 VAC to 240 VAC, 50 or 60 Hz and automatically outputs 90 VDC to the motor, so this unit can be used anywhere in the world without a transformer. All you need is the correct wall plug or converter. Once the on/off switch is switched to the “ON” position, a speed control know is used to vary the speed over the entire range. With the pulley in the “normal” position, the speed range is about 70 to 2800 RPM. In the “high torque” position the maximum speed is cut in half but torque at any given speed is much greater.
This unit can be purchased to replace an existing AC/DC motor on an older Sherline machine, to turn a mill XYZ base into a complete mill so that you don’t have to swap power units back and forth from the lathe or as a stand-alone unit for custom tooling designs. This very compact and well-engineered unit costs far less than other DC units of similar power offered in major industrial tool supply catalogs.
Electric Motor Specifications from Manufacturer
- Type of enclosure: Totally enclosed, non-vented
- Duty rating: Continuous–10 oz. in. at 6100 rpm, .85 amperes; Intermittent–30 oz. in. at 5500 rpm, 1.75 amperes (5 minutes on / 15 minutes off)
- Output horsepower: .06 KW (60 W) at 10 oz. in. / 6100 rpm
- AC voltage (input): Normally 115 VAC, 60 Hz, Single Phase to a rectifier (Sherline electronic speed control converts any input from 100 VAC to 240 VAC, 50-60 Hz.)
- DC voltage: 90V DC to motor (60 Hz)
- Speed in rpm: 6100 rpm continuous
- Class of insulation: Class A, 105° (C.) insulation system
- Normal full load current: .85 amperes
- Starting current: 17 amperes instantaneous starting current (<100 milliamperes). This is also the stall current in True RMS
- Max current at time of changeover from lower speed to higher speed: Depends on load
- Type of motor: 3.00 inch (outer diameter) sub-fractional horsepower brush-type permanent magnet motor
- Temperature rise at ambient 50° C.: Less than or equal to 45° C.
- Motor frame size: 3 inches
- End use of motor: Drive unit for lathe or mill
- Shaft size: 5/16"
NOTE: Electronic circuitry built into the speed control supplies a constant 90 VDC output to the motor regardless of the input current from 100VAC to 240VAC, 50 or 60 Hz, so Sherline machines can be plugged in and used in any country in the world without a transformer as long as you have the correct wall plug converter..
USE WITH AN INVERTER: This motor and speed control can be used with an inverter that produces a sine wave. It cannot be used with an inverter that produces a square wave.
NOTE: In some places in the Sherline literature these may be referred to as 33060 and 33070 with the 5-digit part number. That is from when these were considered “replacement parts” rather than accessories, and we are trying to find and correct instances of the 5-digit number for these two assemblies. If you find one, please let us know and refer to the web page where the error is found.
Download PDF 3306 Instructions