3 Guidelines for Grinding 1 2
Guidelines for Grinding THE OPTIMUM METHOD There is rarely one given, recommended way to handle a particular grinding job. There are usually many different ways to approach a job. Typically, grinding is done with coated abrasives. And the general goal is to achieve the best possible results with the least possible outlay of time, money, and effort. Objectives There are three major objectives in searching for the best grinding method: • The right finish must be considered.
ADDITIONAL FACTORS Effect of Grade on Cut Generally, factors which tend to produce a finer finish will reduce the rate of stock removal. There is a differnce in total cut between the finer and coarser grades. The coarser grades remove more stock faster. Effect of Abrasive Belt on Buffability of Steel The chart shows that a used, 150-grade belt produces a 25micro-inch finish on a given steel. (Micro-inch finish, as used here, refers to the average scratch depth in millionths of an inch.
Effect of Abrasive Grade on Finish The surface finish from a given grade changes as the belt is used. In this example, for the sake of convenience, belt life has been divided into two, uneven segments. The light area represents the first 30% of belt life. The dark area represents the last 70% of belt life. Note that the finish varies less during the last 70% of life than during the first 30%. The lower the reading, the finer the finish. Aused belt tends to produce a finer finish than a new one.
Effect of Contact Wheel Diameter on Finish With all other things being equal, the larger wheel produces the finer finish. Effect of Contact Area on Buffability of Steel Awheel with a smaller contact area may be the better choice where the buffability of steel is a consideration. The small wheel produces a shorter scratch and reduces buffing time. The larger wheel produces a longer scratch that, in the example, requires 50% more buffing time.
Effect of Contact Wheel Serration on Abrasive Belt Efficiency This chart shows the effect of three different types of wheels on belt efficiency. The Serr-X or cross-slotted wheel removes the most stock. Both the serrated wheels will remove a great deal more stock than the smooth face wheel. The curves also indicate a longer belt life for the serrated wheels and show that they remove more stock over a greater number of sheets.
Effect of Contact Wheel Serration on Mineral Wear Slotting the contact wheel has a unique effect on mineral wear. Slotting acts as a self-sharpening agent. Notice the several sharp edges on the enlarged grain used on a serrated wheel . . . versus the flat surface of the grain used on the smooth wheel. This is due to the fact that the grain is presented to the work at a different angle each time it passes over the wheel.
Effect of Lubrication on Micro-inch Finish Lubricants affect the finish as well as the rate of cut. Dry grinding produces the coarsest finish. Oils produce a finer finish, and grease provides the finest finish. Effect of Lubricant on Finish When a lubricant is applied to the belt, the areas between the mineral are filled somewhat by the lubricant. This keeps the mineral from penetrating into the workpiece as far as it would when dry grinding.
Abrasive Belt Sequence for Flat Polishing This chart indicates the finish produced by various heads on a flat polishing line. There are 12 heads in the line. Heads 1 through 4 use grade 100 aluminum oxide. Heads 5 through 8 use grade 150 aluminum oxide. Heads 9 through 12 use grade 150 silicon carbide with oil on the 11th head and grease on the 12th head.
Flat Polishing Production Rate Considerations The production rate is the third consideration to keep in mind in polishing. There are many possible combinations of heads, and no hardand-fast rule is applicable here. Generally, as line speed is increased, more heads are necessary to achieve the same finish. However, stock removal and finish results from any given belt are well known and should be helpful in arriving at a solution. Maximum Line Speed is Limited by these Four Factors 1. 2. 3. 4.
3M coated abrasive products can improve quality, consistency and productivity to help you achieve better results more cost-effectively. For More Information and Assistance: Contact your local 3M coated abrasive products distributor or 3M at the numbers listed below. For the contiguous 48 United States Call. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-800-742-9546 Fax. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-800-852-4668 For: Alaska. . . . . . . . . . . . . . . .
