8.4 Workholding
Micky R. Jennings
Workholding devices on a drill press are designed to securely hold material for hole making operations. They need to be simple, quick, and easy to use. The most common workholding solutions on a drill press are vises and clamps. These solutions come in many different styles but perform the same function of holding the work.
They come in many shapes and sizes, but they share some basic features. The drill vise will have a base that is machined on the bottom so it sits flat on the drill press table. This is to assure that parts will sit flat in the vise for stability and accuracy, and to help establish the primary datum. The top side will have two jaws; a solid jaw and a movable jaw. The solid jaw doesn’t move and is made square to the top surfaces of the vise, creating the secondary datum. The movable jaw is attached to a mechanism that the operator adjusts to put pressure on the part holding it against the solid jaw. The base of the vise will also have some way to attach the vise to the table for heavier cutting operations.
Screw-actuated vise
The screw-actuated vise utilizes a basic unified screw thread, an acme thread or a square thread, to transmit the clamping force needed for workholding. Entry level vises with lower clamping force will be equipped with a 60-degree unified thread, while vises intended for heavier duty clamping will use increasingly flatter threads because of their strength.
Cam actuated vise
A cam actuated vise uses a rod and a friction lever to apply gripping force to the jaws. When in action, the user manually pushes the movable jaw up into the part by putting pressure on the knob at the end of the rod. Once the movable jaw is snug, the lever is pushed downward, and the friction of the camming mechanism increases the pressure on the part, giving added grip strength.
Parallels
Parallelsare used on a drill press in order to raise parts off the table or off the top surfaces of the vise. They are called parallels because the advertised surfaces are ground flat and parallel to one another. They generally come in pairs, and multiple pairs come in a set. For vise use, ⅛” thick parallels are the modern standard of the industry, with a set containing ½” to 1-⅝” heights in ⅛” increments. With parallels used to raise parts off the table, they are usually thicker, ½” or more, so they stand up on their own, and have less incremental change in height.
Clamps are used to hold a workpiece firmly on a table. Tee slots allow clamping devices to grip the table and better secure parts while working. A simple drill press has a table that accommodates clamping devices.
C-clamp
C-clamps, also discussed in Chapter 5, are familiar to a lot of people because they are used in many industries. The main frame of the clamp is shaped like the letter “C”. On one end of the clamp is a pad for gripping, on the other is a screw for adjusting and tightening the clamp. At the end of the screw is another pad for gripping. On