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WORK HOLDING ON THE VERTICAL MILL

The two most common work-holding methods on the vertical mill are securing parts directly to the table by means of clamps or by holding them in a mill vise.
Mounting Directly to the Table Mounting a workpiece directly to the machine table is an excellent work-holding method. The same clamping techniques that you learned in drilling are applied in milling.
Be careful not to distort the workpiece when applying clamping pressure.
In many cases, the workpiece must be aligned with the table or saddle axis to ensure parallel or perpendicular cuts.
A workpiece can be quite accurately aligned by placing it against stops that just fit the table T-slots (Figure J-34).

WORK HOLDING ON THE VERTICAL MILL J-34
Another method is to measure from the edge of the table to the workpiece (Figure J-35). Probably the most accurate method of workpiece alignment is to use a dial indicator fastened in the machine spindle or to the toolhead (Figure J-36). The workpiece is brought into contact with the indicator and the table or saddle is run back and forth while the workpiece position is adjusted so that the indicator reads zero.

WORK HOLDING ON THE VERTICAL MILL J-35 WORK HOLDING ON THE VERTICAL MILL J-36
A precision mill vise may also be used to hold the part being machined. The vise must also be aligned with the table or saddle axis (see Section K, Unit 5). Once again, use a dial indicator for this purpose and always indicate a vise on its solid jaw.
Mill vises are precision tools.
Always treat them gently when setting them down on the machine table. Be sure that the table is clean and that there are no burrs on the bottom of the vise.

WORK HOLDING ON THE VERTICAL MILL J-37
Soft-Jaw Vises Sometimes a mill vise may be equipped with soft steel or aluminum jaws instead of the regular hardened steel types. After the vise has been bolted to the mill table and roughly aligned, a light cut can be taken on the soft jaws. The result of this procedure is a vise jaw that has been machined true to the axis of the saddle or table. Soft jaws are often used in production machining operations or where it
might be desirable to shape the vise jaw in a certain way to hold a particular part to be machined. Another excellent method of work holding is to use a magnetic chuck (Figure J-37). In machining operations, magnetic chucks used to be employed primarily in surface grinding applications. The illustration in Figure J-37 shows a roughing cut made in mild steel (1020 HRs plate). The chuck design also prevents chip buildup on the workpiece. One drawback with a magnetic chuck is that only ferrous materials can be securely held.

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