TABLE OF CONTENTS The objective in heavy-duty grinding is rapid material removal with only secondary concern for surface quality. Removal rates may be so big that the chips are readily visible to the naked eye. Unlike precision grinding, the wheel is usually not periodically dressed.
One important heavy-duty grinding operation is snagging, which is used to condition steel billets and slabs by removing surface defects and scale. Snagging is usually done with resinoid wheels under fixed normal force. The wheel may be either oriented with its plane normal to the workpiece surface or tilted as it is traversed across the billet or slab. Heavy-duty cut-off operations (Figure 3-14) may be either of the fixed-force or of the fixed-feed type. Other heavy-duty grinding processes fall into the fixed-feed category.
Heavy-duty grinding performance depends mainly on the removal rate and wheel-wear rate. A higher removal rate means faster production, and a higher wheel-wear rate indicates increased wheel costs. Wheel consumption with conventional abrasives is usually a minor cost factor in precision grinding, but it is very significant in heavy-duty grinding. There is generally a cost optimum removal rate which balances higher wheel costs at faster removal rates against lower stock removal costs.
The mechanics of heavy-duty fixed-force grinding have been described in somewhat different terms than those of controlled-force grinding (section 5.7), so it is being treated separately here. Material removal in heavy-duty grinding is often expressed in terms of weight instead of volume, but we will use volume for the purpose...
