February 2026 Volume 8

HOW TO PERFORM A COMPLETE MECHANICAL PRESS INSPECTION FOR A FORGING OR STAMPING PRESS By Jeff Fredline MAINTENANCE

U nderstanding the condition of your press equipment is increasingly important. If you don’t take the time to schedule inspections, your equipment will schedule them for you. This article provides a complete step-by-step procedure for inspecting a mechanical forging or stamping press. Keep in mind that a press is designed to provide: • Repeatable tonnage (force) • A perfectly square environment in which the tooling can operate Approaching the inspection process with these two factors in mind helps explain the “why” and “how” behind each check. Performing a complete inspection requires the following equipment: 1. Hydraulic or mechanical jacks large enough to lift the weight of the ram assembly, crankshaft, and gearing 2. Measuring tools such as dial indicators with magnetic bases and feeler gauges 3. Flashlights or other appropriate lighting for the inspection process 4. An inspection form for recording critical data discovered during the inspection Accurate recording of inspection results is critical to the process. Step 1 — Prepare Your Press for Inspection Clean up the area around the machine to allow access to all areas. Place the ram at bottom dead center and perform lockout/tagout procedures. Turn off the air pressure to the machine and exhaust the air from the air counterbalance system. Turn off any hydraulic systems. Special Note: If you are inspecting a mechanical stamping press equipped with hydraulic overloads in the ram assembly, leave air pressure to the overloads on so the hydraulic overload cylinders are engaged. This will allow you to obtain more accurate lift clearance readings when measuring bushing wear. Step 2 — Check Vertical Lift Clearances Place a hydraulic jack on the centerlines of the die space (left to right and front to rear). If you must use shimming blocks to build up the height of the jack, use steel or aluminum blocks. Do not use wood; it can flex under jack pressure and affect readings. Place one dial indicator and base on top of the bolster plate next to the jack. This indicator will be used to measure total lift clearance and to show when all clearances have been removed during jacking. It is best to use an indicator with 1 in. of travel. Adjust the indicator so you have at least 0.500 in. of travel as the ram assembly is lifted.

Apply pressure with the jack until the needle on the indicator stops, then record the total movement in thousandths of an inch. This value is the total lift clearance for the machine. Record it on your inspection documents. Next, measure clearance at the next connection point (for most machines, the wrist-pin bore). Place a second indicator and magnetic base to measure from the upper connection to the ram, leaving the original indicator next to the jack. Once the indicator between the upper connection and the ram is in place, zero it and repeat the jack test. Watch the indicator between the upper connection and the ram and record the reading. Next, measure the clearance between the upper connection and the crankshaft bushing. Move the indicator from the upper connection to ram position to the upper connection-to crankshaft position, then repeat the jack procedure and record the measurement. The final vertical-lift-clearance measurement is clearance in the main bushings. Check both the left-hand (LH) and right-hand (RH) main bushings. Use an additional indicator and base—one between the crankshaft and the frame on the LH side and one on the RH side. Using the jack, repeat the lifting procedure and record the readings for both sides. Example: 1,000-ton press • Total lift clearance: 0.210 in. • Upper connection to ram: 0.065 in. • Upper connection to crankshaft: 0.086 in. Figure 1 shows the layout of a mechanical stamping press. Forging presses are similar, but they do not use the nut housing assemblies. They still use a wrist-pin-and-bushing arrangement to attach the ram to the upper connection. Because the ram and connection assembly can shift slightly, the individual connection point readings may not add up exactly to the total lift clearance. It is also common for the main bushing on the bull-gear side of the press to show slightly more wear due to the weight of the gear and clutch assembly. The next step is to determine whether the clearances detected are within acceptable running tolerance. For rotational clearance in a press, the standard running clearance is 0.001 in. per inch of shaft or pin diameter up to 12 in. diameter, and then 0.0005 in. per additional inch over 12 in. Example: 24 in.-diameter shaft • 24 in. - 12 in. = 0.012 in. clearance • Plus 12 additional inches at 0.0005 in. per inch = 0.006 in. • Standard tolerance for 24 in. rotational clearance: 0.018 in. • Main bushings (RH): 0.045 in. • Main bushings (LH): 0.038 in.

FIA MAGAZINE | FEBRUARY 2026 17