Auto Service World
Feature   May 1, 2000   by CARS Magazine

SSGM Tech Tips (May 01, 2000)

Reconsider contactsContacts can be a problem. Not the kind in switches and relays, but the kind you may be wearing to correct poor vision. Modern soft contact lenses are gas-permeable for all-day comf...


Reconsider contacts

Contacts can be a problem. Not the kind in switches and relays, but the kind you may be wearing to correct poor vision. Modern soft contact lenses are gas-permeable for all-day comfort, but the same feature can allow fuel, solvent, and other vapours to pass through the lens and contact the surface of the eye. And once the chemicals are there, they stay trapped against the eye for the rest of the day. Contacts are prohibited in most chemical labs, many of which never deal with compounds as potentially hazardous as those in a service bay. Long-term exposure may have unknown consequences, so why take chances? If contacts are a must, remove and clean periodically.

Clips for hands-free testing

Use a multimeter for electrical circuit testing? Spring-loaded hook-type testing clips grab small leads and relay, switch or board pins without shorting or falling off. They’re available at electronic supply dealers and open with a thumb-operated plunger like a hypodermic needle. Solder a lead, preferably instrument wire, to the clip and a matching plug for the meter to make custom sets. For bigger jobs, alligator clips can be crimped around the probe ends for hands-free work. Don’t forget to colour code the leads for polarity.

Spark test for hardened steel

Ever ruin a perfectly good file on a part you thought was mild steel? A bench or pedestal grinder can help you determine whether a steel part is hardened or not. Gently touch a portion of the part to the wheel and observe the sparks ejected. Continuous ribbon-like streams of spark indicate a softer part, likely mild steel. Bullet-like “shooting star” spikes suggest a hardened part. If it’s necessary to grind a hardened part, don’t use the conventional ferrous grey wheel. Choose a wheel designed for the purpose, and, like any grinding wheel, true the surface with a dresser. And, of course, an approved face shield and gloves should always be worn, right?

Compound for thread clean-up

Stuck with an irreplaceable bolt or stud with galled threads? A little valve-grinding compound on the threads lets you run a nut up and down the fastener, lapping the two together. Remember to thoroughly clean off any compound and use either anti-seize compound or sealant as required for the application. Don’t use this technique if you have the appropriate die, which is always the preferred thread clearing tool. If you’re cutting new threads with a die, use a thread-cutting oil for a better finish. Remember to back off a quarter of a turn after each full turn to break chips, and use an air gun or small paint brush to keep the working area clean. For critical bolts, always replace.


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