Tech Talk
What are “Steady-Rests”?
There are four types of steady-rests. 1. Open fixed steady-rests with manual adjustment. The open steady rest has two jaws and is manually adjusted. It does not allow grinding in the position of the steady-rest, as the size diameter will change and require adjustment in process. This type of steady-rest is used on a machined diameter which is not ground. The two-jaw has manual adjustment from a single knob or screw which moves both jaws in unison to a diameter. Another type of open, fixed, and manually adjusted steady-rest has a third support opposite the bottom bearing which secures the workpiece in a manner which prevents climbing of the back bearing. Polyamide materials are generally used for the steady-rest bearings. These materials wear rapidly, however, they leave little evidence of their seating on the workpiece surface. These steady-rests are predominantly used for single and small batch productions.
2. Open steady-rest with auto diameter adjustment. This type of steady-rest has two jaws which automatically adjust to the part diameter. The jaws travel towards the workpiece until contact is made; at that point the jaws are clamped with collets and can no longer be adjusted. Adjustment can only be made after retraction of the jaws. The workpiece may be loaded without restriction, as the jaws are retracted when the workpiece is changed. Grinding is not normally carried out in the support area. The steady-rest is usually seated n a premachined diameter. This type of steady-rest is used for medium batch production machines.
3. Open steady-rest with diameter dependent follow-up. This steady-rest operates automatically. It is diameter dependent and utilizes an in-process gage to feed back the part diameter to adjust for the jaw position. Alternatively, CNC may be utilized to achieve the follow-up. This type is used in conjunction with an automatic taper correction device and is used for high batch production.
4. Closed fixed steady-rest. A closed fixed steady-rest is used on a premachined surface. It gives optimum support and achieves the finest accuracy. The workpiece is captive and allows plunge grinding of long workpieces. The very rigid support provides the rigidity to suppress self-excited vibration. This type of steady-rest does not allow grinding in the position of the steady-rest. Setup time for a closed fixed steady-rest may be lengthy. This type of steady-rest is used for high precision grinding or very long workpieces where more than one steady-rest might be used along the length of the workpiece.
