In through-feed grinding, the grinding wheel is set at a fixed distance from the control wheel as in Figure 19.9. Through-feed is employed for longer workpieces and also for a continuous stream of short workpieces. In most cases, the length-to-diameter ratio of the workpieces is greater than one.
The workpiece is fed between guide plates into the space between the grinding wheel and the control wheel. The axis of the control wheel is inclined at a small angle, Ф, to the horizontal so that the axial component of the control wheel speed drives the through-feed motion. The rate of through-feed depends on the angle of inclination of the control wheel.
The surface speed of the workpiece in stable grinding is normally equal to the surface speed of the control wheel. Differences in workpiece and control wheel surface speed are usually negligible. The resultant workspeed, vr, can be resolved into two components. By convention, the slowest component of workspeed is termed the feed speed, vf, and the fastest component is termed the workspeed, vw. The workspeed is, therefore, the circumferential component of the resultant work — speed and the through-feed speed is the axial component.
Vw = vr • cosФ (19.19)
The surface speed of the control wheel has a horizontal axial component that provides the axial feedrate of the workpiece otherwise known as the through-feed speed:
vf = vr • sinФ (19.20)
where Ф is the angle of inclination and vf is the feedrate.