9.4 Work Holding
Micky R. Jennings
Work holding devices on a milling machine are designed to securely hold material for various operations. They need to be simple, quick, and easy to use. The most common workholding solutions on milling machines are vises. These solutions come in many different styles but perform the same function of holding the work.
Mill Vise
A 6″ mill vise is a common work holding device on a milling machine. The vise of a milling machine is generally of higher quality than that of a drill press vise, with added rigidity, precision, size, and mass. The milling vise is most often clamped to the table of the milling machine with the solid jaw parallel to the table’s movement. The vise has a body with precision ground top and bottom to give a reliable platform for the work or parallels to sit on. At one end, a solid jaw is mounted. The solid jaw gives a precise vertical surface that is perpendicular to the base and often aligned with the side-to-side motion of the table. At the other end of the vise is a movable jaw and a screw that gives it movement. The movable jaw moves in and out with the twisting of the screw, and clamps work against the solid jaw. The movable jaw is also capable of slight rotational movement in order to clamp work surfaces that aren’t perfectly parallel.
Fixture Clamps
Fixture clampsgenerally come as a clamping kit. The kit will contain T-nuts, studs, regular nuts, risers, extensions, and the clamps themselves. When in use, the operator will select the components needed to clamp the part to the milling machine table. The end setup will have a clamp spanning a short gap between the part and the riser. In the middle of the gap will be the stud, the T-nut in the table, and the regular nut tightened on top of the clamp. The clamp must be level or slightly lower on the part side. This makes sure the tip can grip correctly on the part. The bolt must also be as close to the part as possible. With the bolt close to the part, a greater percentage of force is put into the part rather than the riser. If the bolt is closer to the riser, the majority of the holding force is put into the riser, and there is potential for the part to come loose inadvertently.
Attributions
- Figure 9.33: Mill vise by Micky R. Jennings, courtesy of Wenatchee Valley College, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 9.34: Fixture clamp use with the stud closest to the material by Micky R. Jennings, courtesy of Wenatchee Valley College, for WA Open ProfTech, © SBCTC, CC BY 4.0
A primary precision work holding device used on a milling machine.
Clamps that utilize the tee slots of machine tables as anchors for securing work.