Shaft Straightening Press: Applications, Design and Controls

Heat treating, machining and forming all do the same thing to a long shaft. They warp it. And a warped shaft won't machine right, won't run true, and won't pass inspection.

That's why shops in aerospace, oil and gas, marine and automotive rely on a shaft straightening press. A hydraulic straightening press gives you tight control over the process, so you get accurate, working parts at a reasonable cost. Other methods exist. But when you need to prep the material so the part can be machined properly, straightening is often the only real option.

What a straightening press can handle

A hydraulic straightening press isn't just for shafts. It also works on:

• Shafts of all sizes, including large diameter shafts several inches across and up
• Plates
• Large weldments

Weldments are a good example. The heat from welding can warp or distort them. It's smart to straighten them before moving on to secondary operations.

Shafts are trickier. They come in so many sizes that automating the straightening process is hard. That's why press design and operator control matter so much.

Choosing the right press design

Most fabricators pick between two designs: a fixed head press or a moving gantry press.

For plates and weldments, a moving gantry press is the way to go. The head can travel over the work, left to right or front to back, wherever the part sits on the bed.

For shafts, a straightening press usually works on a single axis, centered on the shaft so it can move easily.

For large drive pipes and shafts that are hard to handle, like the ones used in oil field work, you want a press that can locate to the high spot. That lets you work the bend while applying tonnage to straighten it. Depending on the size of the shaft or pipe, you can also reposition the part to make the job easier.

How a traveling gantry press straightens large shafts

Large diameter shafts are usually straightened on a traveling gantry press. Here's how it works:

• The gantry moves along the X axis, while the main cylinder provides the Z axis down stroke to engage the shaft.
• All the straightening happens centered under the main ram, as the gantry travels over the area that needs work.
• The gantry can move to the end of the press, so the operator can load shafts from an overhead crane without fighting the machine.
• Once the shaft is loaded, the operator drives the gantry nose tool over the high spot and straightens it.

When a shaft is too big to load by hand, an overhead crane lifts it into place. Hydraulic traveling carriages then raise and lower the shaft on and off the V blocks. The operator lifts and rotates the shaft through the process until it's within acceptable tolerances.

Why control matters

The right shaft straightening press gives the operator full control of ram movement while applying tonnage. Less control means more hits to get the part straight. A good press lets the operator dial in ram depth in 0.001 inch increments.

Straightening press controls, explained

Here's what the main controls on a gantry straightening press do:

• Auxiliary power unit: Powers the carriage and lift assemblies. It's only needed for shaft work, so you can shut it off when straightening plates or weldments.
• Carriage up/down switch: Raises and lowers the carriage assemblies so the part can be rotated to find its high spot.
• Lift assembly up/down switch: Moves the live centers that hold the shaft.
• Head and gantry lock: Pulls the gantry up against the bottom of the press bed while straightening. This holds it in place so it can't tip or shift off center.
• Down pushbutton: Part of the anti-tie-down, anti-repeat two-hand control. Under OSHA requirements, both of the operator's hands must be engaged at the start of each cycle: one on the cycle start button, the other on the ram joystick.
• Motor on/off: Turns the motor on and off.
• Gantry movement joystick: Moves the cylinder assembly front to back and the gantry left to right.
• Main ram joystick: Controls ram extension and retraction. The ram can also be controlled proportionally for speed and pressure.

Built by people who know straightening

Press Master has served machine shops for 45 years. We design presses that get the job done efficiently, safely and reliably.

Want to see what we build? Check out our hydraulic straightening press, or contact us to talk about your shaft straightening press.