Foredom Electric Co. is marketing a state-of-the-art brushless micromotor unit that delivers smooth, controllable variable speed (1,000 to 50,000 rpm) with high torque. The small benchtop control features an on/off switch, digital speed display and control knob, indicator lights, forward/reverse selector, hand/foot-pedal selector, and an automatic-cruise switch. The lightweight hand-piece motor measures 6.3 inches long by 1.06 inches in diameter and has a 3/32-inch or optional 1/8-inch collet. The features of the new micromotor unit are revealed in the following project and examples.

The Foredom micromotor kit 1050 shown in this project includes the control unit, hand piece with a 3/32-inch collet, variable-speed foot control, hand-piece cradle, and an extra fuse. The kits are available in 110 or 220 V and can be found at most tool and equipment suppliers.

1. This wedding band was made using Foredom’s high-speed, high-torque micromotor to refine and manipulate fitting of the cast parts. I found the precision process of the fit to be tremendously aided by the smoothness and power of the micromotor.

2. The micromotor control unit is small and fits nicely on the bench top. In this image, I removed (by hand sawing) the 18k yellow gold decorative pattern from its multiple-sprue system required for casting.

3. After removing the sprue system from each half of the decorative trim pieces, I used 3M flex diamond rotary abrasives to remove the remainder of the sprues and to smooth the back of the parts. It was critical to the fit that the backs were even and conformed to the surface of the band. I controlled the speed of the unit for this procedure using the variable-speed foot pedal. I found the torque to be unwaveringly constant at all speeds.

4. Changing tools for each of the procedures was effortless. The hand piece features a secure, easy-twist release and locking system.

5. After smoothing the back portion of the two decorative trim pieces, I created a small divot under the widest area of each motif in the pattern. I used an aggressive-cutting high-speed steel ball bur for this process and set the speed on the control box to deliver a constant 30,000 rpm. The cutting was easily controlled, since the bur did not wander at this speed. I used a fresh charge of bur lubricant for each divot to keep the bur sharp and prevent overheating.

6. The band portion was cast using 950 palladium by TechForm, Portland, Ore. After removing the sprues, I smoothed the band using Foredom’s rubberized CW ceramic polishing wheels. They run relatively cool at high speeds and are available in six different grits ranging from 120 to 1,500, making them ideal for this purpose.

7. After fitting the parts, I backfilled the small divots created on the backs of the trim pieces with 14k white gold easy solder. Then I placed the trim pieces onto the band and soldered them in position. In this image, I’m completing the soldering process.

8. In this example, I used the micromotor to set a 1.00 ct. round diamond in a heavy prong solitaire mounting. To create the bearing, I used a high-speed steel setting bur that was slightly smaller than the diameter of the diamond. I used a slow controllable speed between 2,500 and 4,000 rpm, using the foot pedal option. The torque was powerful and the burring smooth. The connector cord between the control unit and the rotary hand piece is very flexible, and the motor runs quietly and evenly. The torque remained consistently strong throughout each procedure. All of these features contributed to an easy, flawless bearing-cutting operation.

9. I also used the micromotor kit to finish and smooth several milled waxes. The true rotation of the mounted cutting tools along with the controllable speed and constant torque made cleaning up even delicate, fragile waxes simple and easy.