Knee mills are more flexible than bed mills in terms of the materials and projects they can handle. However, a bed mill offers greater rigidity and stability which makes it better suited for heavy-duty tasks.
For example, on a knee mill you can swivel the head and tram it into a tall angle plate to machine a part that extends beyond the table's travel. This is not possible on a bed mill.
Knee Mills At first glance, all knee mills look very similar. They feature a tiltable head, a movable ram and turret, and a slotted table that can clamp a variety of workpieces. A skilled machinist can make just about anything on a good quality manual knee mill.
They are usually simpler and more versatile than bed mills. For instance, you can easily clamp a block to a knee mill’s table, drill a few holes, and then mill a keyway in the end. You would have to build special fixtures to accomplish the same task on a bed mill. Knee mills also allow you to swivel the head and stretch the ram to reach inaccessible areas. This is difficult to do on a bed mill without expensive fixtures. They may also be less expensive and easier to maintain than a bed mill. Unlike bed mills, many knee mills can be used on single-phase power found in homes. This allows them to be purchased by hobbyists and those new to machining.
Bed Mills A bed mill is ideal for machining larger, heavier workpieces. It’s more stable than a knee mill, and can handle bigger projects with ease. It’s also known for its accuracy and precision, making it the choice for industrial applications.
To use a bed mill, start by loading the desired tool into the machine’s tool changer and ensuring that it’s secure. Next, run the program and monitor the process to ensure that everything is going according to plan. Once the milling is complete, carefully remove the finished product from the machine. BM-C and BM-BL bed mills feature interchangeable slides, rams and columns to ensure the machine is able to perform heavy duty cutting operations with ease. This modular configuration also endows the machines with enhanced rigidity and precision, preventing workpiece deflection. To prevent this, the oversized ram and slide systems have reinforced ribbing that’s designed to withstand high loads and intense cutting conditions. The sturdily built table can also withstand high-load cutting without causing the machine to “knee rock” or suffer from table sag.
Fixed Bed Type
Like their name suggests, fixed bed type bed and knee milling machines have a bed that is rigidly attached to the machine. These types of milling machines are also referred to as manufacturing type milling machines or plain machines. These types of milling machines can perform cutting operations in horizontal and vertical directions.
The advantage of the fixed bed design is that it provides more stability for machining at high speeds. This is one of the key factors in achieving precision in machining. The structure of the fixed bed is critical for ensuring that the milling process is accurate and efficient. Another key feature of the fixed bed design is that it enables the use of a quill. A quill moves just the spinning part of the spindle, not the motor, up and down in a similar way that a drill press does. This allows the mill to machine at an angle, something that is not possible with a knee mill.
