Chapter 3 Brake Tools, Shop Equipment, and Service Information 43 Copyright by Goodheart-Willcox Co., Inc. remove any hard spots, which are raised areas that cannot be removed with the regular cutting bits. A drum grinder is illustrated in Figure 3-36. Warning: If you must arc grind a set of brake shoes, be sure the vacuum motor and HEPA filters are operating and wear a respirator. Hydraulic Press It is almost impossible to do brake work without some sort of hydraulic press. Presses are used to replace broken studs, remove hubs from bearings, install brake shoe retaining pins, and many other jobs. Th e hydraulic press is a common piece of equipment found in most shops. Figure 3-37 shows a common make of hydraulic press. To make the best use of a hydraulic press, it must be equipped with various adapters. Pressure Bleeding Equipment Th e pressure bleeder is designed to force clean hydrau- lic fl uid into the system and force out contaminated fl uid and air. Pressure bleeders eliminate the need for a helper to pump the brakes, and the bleeding procedure takes less time. To use the bleeder, fi ll it with new, clean brake fl uid. Warning: Never mix glycol (DOT 3 and 4) and silicone (DOT 5) fluids. Install the proper adapter to the master cylinder. Aft er the tank is fi lled with fl uid, use shop air to pressurize the tank, usually to about 15–20 psi (103–138 kPa). Th en, attach the bleeder using the proper adapters and open the fl uid valves. Th e vehicle can then be bled normally. Some pressure brake bleeders are electrically operated. An electric pump provides the bleeder pressure, eliminating the shop air connection. Vacuum Bleeding Equipment Th is hand operated vacuum bleeder, when pumped, creates a vacuum in the attached jar. It is connected to the brake lines via the bleeder screws and pumped to develop vac- uum. Vacuum causes brake fl uid to fl ow into the jar when the bleeder screw is opened. Figure 3-38 depicts a vacuum bleeder. Care of Tools Just as important as obtaining the proper tools is maintain- ing them properly. Tools that are misused are much more likely to break, or to slip and cause injury. Th e following are a few rules for the proper use and care of your tools: • Always use the proper tool for the job at hand. • Store tools in an orderly manner. • Clean tools before returning them to storage. • Clean and lightly oil tools that are prone to rusting. • Repair or replace any damaged tools. Silencer band Brake drum Grinding wheel dresser Tool post pivot setscrew Cross feed handwheel Grinding wheel Boring bar clamp Ammco Figure 3-36. One type of electrically driven brake drum grinder. For a proper finish, keep the stone dressed. Note the stone dresser. Goodheart-Willcox Publisher Figure 3-37. A manually operated, floor-mounted, hydraulic press.