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Patching drywall Problem: A piece of drywall has a large hole that cannot be patched by spackling alone.
By Staff October 1, 2000

Patching drywall

Problem: A piece of drywall has a large hole that cannot be patched by spackling alone. Is there a way to easily do the job?

Solution: Cut a piece of cardboard bigger than the damaged area and poke a small hole in the center. Thread a piece of string through the hole and tie a knot on one side so it cannot be pulled out. Place the cardboard into the hole and pull the string until the board is tight against the backside. Spackle the cardboard into the wall. Once the first coat is applied and dries, cut the string and finish spacking until the wall is smooth.

Contributor: Brian Keiser, RMF Engineering, Inc., Baltimore, MD

Aligning leadscrews

Problem: It is extremely important for a machine tool to have the leadscrew perfectly align with the direction of travel. If not properly aligned, noncompensable positioning errors and premature leadscrew and ballnut wear result as forces produced by the misalignment tend to shift the sliding carriage (table) away from the ways and put the leadscrew into a bind. Adjusting or verifying the alignment presents a challenge for a mechanic. Is there a way to do the job?

Solution: Hook up an ampere meter clamp to one of the wires feeding the motor. Run the motor at a constant feed rate in order to move the table from the very left to the very right end. If there is a misalignment, the electrical current drawn by the motor steadily increases as the ballnut gets closer to the fixed bearing. Tighten the adjustment screws lightly on the ballnut and exercise the table several times so the ballnut can position itself relative to the table. Tighten the adjustment screws firmly and monitor the motor current. The leadscrew is perfectly aligned if the current fluctuation is less than 2% and no tendency is present along the full axis travel. Repeat this process if necessary. Loosening and subsequently tightening the screws securing the motor may also be required. Contributor: David Gluzman, Sulzer Carbomedics, Inc., Austin, TX

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