Manual Machining

Unlike CNC systems, manual machinery requires much more manual intervention to operate. Like anything, there are pros and cons of this approach. For less complex geometries, it is often much quicker and therefore less expensive to manufacture components on a manual mill or lathe. For example if you had a requirement for a couple of pieces of a square plate with a couple of holes bored into it, the time to program this on a CNC would outweigh the benefits of automation. In a manual machine you would set the part up in a vice, indicate a datum for the part per the print and then start machining, thereby dramatically reducing the overall time to complete. If on the other hand you have hundreds or thousands of this same part, it would likely be a much better, and overall less expensive option to manufacture on a CNC, as once the program is created the amortized cost per part is very minimal in large runs, and you gain the advantage of consistency and reduced downtime associated with the CNC. Additionally, requirements that have complex geometries or surface features, are often easier to run on a CNC, where the program can help with some of the math required in calculating tool paths, as well as coordinating multiple axis of motion together to create contoured surfaces, which are very difficult to replicate on a manual mill, where dials or cranks are required to operate each axis individually.

Technology has advanced in the area of manual equipment and there is a multitude of upgrades and accessories available in industry to add advanced capabilities to the machine. Options exist that enable a manual tool to incorporate some base level CNC functionality, like the ability to upload g-code programs into the tool and even run coordinated motion (multiple axes running at the same time along a predetermined tool path). Other options exist and are common place, such as digital readouts, that give a graphical user interface to see the exact position of the table and spindle positions, which makes operation much easier than using markers on a dial to indicate location. These indicators, which are tied to linear encoders (a digital, electronic scale mounted on the side of the moving axis) can also enable higher precision, and often improve the overall tolerance capability off the machine. Other accessories such as a Power Feed, allow the operator to automate motion of a single axis of the machine without the need to manually turn a crank. When engaged, an electric motor drives the screw of the table until a set location is reached and the operator disengages the feed system.?

Manual Lathe

The operation that a Lathe performs is commonly referred to as “turning”, as the part to be machined is housed on the spindle and rotated or turned. The major difference between a mill and a lathe is that the lathe holds the work piece in the spindle and therefore rotates the material to be machined relative to a stationary cutting tool. The speed at which the spindle (the element that holds the work piece) spins is referred to as the Spindle Speed or often just Speed. The rate at which the tool moves relative to the work piece (movement along an X or Y axis) in one given revolution is referred to as the Feed Rate or just feed. Once the spindle is in motion and spinning at a high rate of speed, a static tool (e.g. cutting tool) will come in to make contact with the surface of the work piece and then traverse slowly (feed) along the surface of the part removing material and bring to a desired dimension. This process is used to machine a wide variety of parts, although probably most ideal to produce round or cylindrical geometric shapes.

Generally speaking Lathe Equipment can come in one of two design configurations, Horizontal Lathes or Vertical Lathes. The functional elements of the lathe are fairly uniform between the configurations and the Manual Lathe diagram calls out some of the common components of the machine. In a lathe the Spindle is the rotary element powered by an electric motor. The Headstock assembly houses the spindle along with the bearing set, gearing and other elements required to support and drive the spindle. The Spindle houses a Chuck which functions the same as a vice does on a milling machine and clamps on the work piece to be machined. The spindle sits opposing the Tailstock and tooling. The Bed of the lathe is base where the other main components are mounted and tied together. This is a rigid, structural member that connects the Headstock with the Tailstock and the Carriage, and makes sure that are remain aligned. The Carriage is the moving member that holds the tooling and moves in and out on the x-axis to engage the main spindle chuck and work piece. The Tailstock is used to support the opposite end (or free end) of the work piece to stabilize the part as it rotates. Imagine a long bar that needs to be machined. If one end is held in the chuck on the spindle, and the other end sticks out more than multiple inches, once the spindle starts spinning the unsupported end will whip, and prevent accurate machining as well as creating damage. To prevent this the tailstock is positioned into place near the free end of the part and a tailstock quill, which has a tapered end, is extended to come in contact with the free end of the part. Now when the spindle starts to spin, the quill spins with the part and keeps it supported.

In a horizontal lathe the relative motion of the carriage and tailstock happen side to side or right to left in front of the machine operator and the spindle sits parallel to the floor. Horizontal are more common in industry than Vertical lathes, but both have their place. For example horizontal lathes are able to turn much larger materials, as they are not restricted to ceiling height as in a vertical lathe. Horizontal lathes are generally more flexible and optimal for large volume production runs.

Vertical and Horizontal Lathes are essentially the same equipment with the same components, however the vertical lathe has been essentially flipped up on its end. In this case the spindle sits perpendicular to the floor and the carriage traverses up and down inside the machine. One major advantage is that because the work piece is oriented to take advantage of gravity, vertical lathes can often support much larger and heavier projects. Consider that in a horizontal orientation, a large heavy part, will be fighting gravity as it turns and will naturally want to deflect down and create a whipping effect. A downside of vertical equipment is that because the work table and work holding sit below the tooling, it is more difficult to keep the part clean during machining. As the part is being machined, chips will inevitably rest on top of the part. In a horizontal lathe gravity works to your advantage here and the chips fall off to the chip pan which sits below the working area of the machine.

Manual Mill

A milling machine or mill for short, functions by spinning at very high speeds, a cutting tool (e.g.- a mill or drill) relative to the work piece (or part to be converted from raw material into finished good) which is held stationary. The work piece is moved in very slow relative motions in coordination with the cutting tool. When the high speed cutting tool comes in contact with the raw material it starts to shave away the surface layer of the material in small chunks or chips. A good analogy for this would be the way a chisel works on wood, or even a knife through butter. As the cutting tool takes more and more material off, the automated controller continues to extend the tool into the part until the desired shape or dimension is achieved. The speed at which the spindle (the element that holds the cutting tool) spins is referred to as the Spindle Speed or often just Speed. The rate at which the tool moves relative to the work piece (movement along an X, Y or Z axis) is referred to as the Feed Rate or just feed. The Speed and Feed rates are very critical and need to be highly controlled to conform to the unique characteristics of different materials, cutting tool types, and features being machined.

In a manual mill there are three separate axis of motion; X, Y and Z-axis. Two of these axes (X and Y) rest on top of the Knee of the machine which is a heavy casting attached to the Column of the machine. The Knee is mounted on a dovetail guidance system which it allows it to be raised and lowered relative to the floor using hand crank. The Column is an integral piece with the Base of the machine. The Base, as the name implies is the foundation, and the Column runs vertical up from the base towards the back of the machine, providing a mounting point for the various other elements. A Saddle sits on top of the Knee and has a guide way that allows motion via a crank in and out, or in the Y-axis. The Table sits on top of the Saddle and runs side to side or in the X-axis, also via a crank. The Table is often outfitted with a power feed as discussed above to automate the X-axis motion. A vice or work holding element can then be mounted to the table. The Ram is mounted at the top of the Column and sits out over the Table. The Ram houses the Spindle which is a rotary shaft that spins the cutting tools. The Quill provides vertical or Z-axis motion for the spindle, when a handle is pulled or (when outfitted) a power feed accessory is used to automate the motion.

Metal is perhaps the most common material type to be machined on these machines, but these machines can also process various plastics, woods, composites and ceramics along with myriad other elements and compounds. Metal machining ranges from carbon and stainless steels to aluminum alloys to brass and copper to a variety of specialty and exotic metals like Inconel, Hastelloy, etc.

Generally speaking any machining operation, whether CNC controlled or manually operated, is optimal for industries and applications that a require removal of metal from a raw material to reshape it into a specified dimensional footprint or with specific dimensional features. Some example operations include-

? Drilling of holes for mounting- e.g. screw holes, clearance or access holes, ports, etc.

? Threading of holes

? Boring or opening up holes- e.g. - enlarging a hole in a casting to a specified dimension

? Milling of a planar surface (referred to as face-milling) to achieve a flatness or straightness specification?

? Surface contouring- to achieve unique surface geometries

? Gear cutting

? Machining of grooves in a round part- e.g. bearing seats, seal seats, etc.

? Surface contouring- to achieve unique surface geometries

? Tapering of a round part

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