Prior to the advent of computer aided drafting, draftspeople made technical drawings on drafting tables. The parallel bar was used in place of a T square. The parallel bar had the advantage of being held in position by a long wire running around the perimeter of the board. This setup allowed the bar to remain stationary when in use. Over time, the wire’s mounts can come loose causing the bar to stop working. Follow a few simple steps to repair a drafting board with a parallel bar.
Flip the drafting board over. Place two or three towels underneath the surface of the drafting board to protect the parallel bar. Spread the towels out so they cover an area equal to the size of the board. Lay the board on the protected surface.
Examine the pulley mounts. The wire used to move the parallel bar up and down is mounted on a series of pulleys, which are in turn mounted to the drafting board with screws. Over time, the screws become loose, causing the wire to become slack. Place each pulley between your thumb and index finger. Try to move the pulley from left to right. If the mounting screws are loose, the pulley will shift to one side or the other.
Tighten the pulley’s mounting screws. Most pulley mounts are held in place with a Phillips screw. Use a Phillips screwdriver to tighten the mounting screws. Turn the screw clockwise to tighten it. Turn the screw until it is firmly in place.
Check the pulleys for dirt and debris buildup. Because the pulley is greased, dirt and debris can build up within the pulley’s channel over time. Buildup forms on the pulley’s outer edges, causing the wire to stick when you move the parallel bar up or down. Check each of the channels for dirt or debris.
Clean the pulleys. Dip a cotton swab in rubbing alcohol. Rub the tip of the swab gently into the exposed part of the pulley’s channel. The wire rides along a small section of the pulley, leaving the majority of the pulley’s channel exposed. When the dirt and debris loosens, remove the small chunks with a pair of tweezers.
Examine the parallel bar’s mounting screws. Over time, the bar’s mounting screws will become loose. The mounting screws hold the parallel bar’s pulleys in place. If the screws are loose, the pulleys will not function properly. Use a Phillips screw driver to tighten the mounting screws.
Remove any dirt and debris from the parallel bar’s pulleys. Use a cotton swab dipped in rubbing alcohol to remove any dirt and debris from the bar’s pulley channels; rub the exposed channel with the swab’s tip. Llift off any debris clumps with tweezers.
Lubricate the pulleys. Use spray lubricant to grease the pulley channels. Place the nozzle into the pulley channel, and spray it lightly. Repeat the process for each pulley.