Is your milling machine’s auto quill feed lever locking in but the quill stubbornly refusing to feed? Many milling machine owners, especially those with Bridgeport-type mills, encounter this frustrating issue. If you’re facing a similar problem with your milling machine, particularly models like the MFI Australia “Quantum” or those made by JiH Fong machinery company, you’ve come to the right place. This guide will walk you through the likely culprits and how to approach repairing your milling machine’s auto quill feed.
The most probable cause for a non-functioning auto quill feed in Bridgeport clones points to the gear train responsible for powering the downfeed. This system typically draws power from the spindle itself, located in the head just below the belts. The power transfer initiates with the engagement of a worm feed cradle to a worm gear on the spindle.
From there, a right-angle bevel drive gear at the end of the worm cradle plays a crucial role. It meshes with another gear, directing the power downwards into the three-speed gear changer mechanism. If your quill feed is entirely unresponsive, the issue is likely a sheared key. This key could be on the worm feed bevel gear or its counterpart situated on the vertical shaft. Another potential location for a sheared key is on the forward/reverse shaft, which is controlled by the direction lever at the front of the milling head.
In some instances, the problem might be less severe, such as damaged gear teeth. For example, a bevel gear with missing teeth on the worm cradle might cause intermittent feed operation, working only during certain rotations. In such cases, replacing the damaged gear, and potentially its mating gear, is the necessary fix.
It’s important to understand that these downfeed systems, while convenient for tasks like boring with minimal pressure, are somewhat delicate. Milling machine manuals often specify limitations, such as a maximum drill size (e.g., 3/8″) when using the power downfeed. Overloading the system, particularly by attempting to drill large holes using the auto feed, is a common cause of broken gears and sheared keys within the quill feed mechanism.
Repairing your auto quill feed typically requires a systematic disassembly of the milling machine head to pinpoint the exact problem. While this might sound daunting, it’s manageable if approached methodically. The first step usually involves removing the motor. The subsequent process is similar for both belt-driven and variable-speed models as the area of concern lies below the motor level. Having a detailed repair manual for your specific milling machine model is absolutely essential for this task.
A helpful tip for safely removing the often heavy motor is to use your milling machine table as an elevator. Once the motor is detached, rotating the head by 90 degrees to the right can provide better access to the internal components of the quill feed mechanism.
Repairing your milling machine’s auto quill feed requires patience and a systematic approach. By carefully disassembling the head and inspecting the gear train, you should be able to identify the broken component, whether it’s a sheared key or damaged gear, and restore your milling machine’s auto quill feed to proper working order. Good luck with your repair!
