User manual 3M GUIDELINES FOR GRINDING

[. . . ] Changing any of these variables will affect the surface finish. It will also affect the rate of cut and the life of the abrasive belt. If, however, these variables can be isolated, they will cause effects in a scientifically predictable way. Results Knowledge of the effects of these variables will help to obtain optimum results. This knowledge will allow you to vary and manipulate them to maximum advantage. [. . . ] 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 Finish Serrated wheels do not produce as fine a finish. The more aggressively the wheel is slotted or serrated, the rougher thefinish. Effect of Contact Wheel Area on Pressure The amount of pressure per square inch exerted against a piece of work will affect the rate of cut and belt life. This chart shows how various slotted and serrated contact wheels affect pressure. Given a total pressure of 100 pounds and a tangential contact area of two square inches, the plain face wheel applies a pressure of 50 psi. Acontact wheel with a standard 1-to-1 ratio yields 100 psi. The scoop serration at a ratio of 3 to 1 provides 200 psi. With a SerrX wheel and a 4-to-1 ratio, the pressure rises to 250 psi. In other words, with total pressure remaining constant, the pressure per square inch rises in proportion to a decrease in land area. Impact Effect of Contact Wheel Slot Angle The angle of the contact wheel slot also affects rate of cut and belt life. The 90° or straight across slot is the most aggressive grinding angle, and creates the highest impact on the work. The reason is that inertia causes the workpiece to slip into the voids and the impact of the following lands drives the mineral deeper into the work with a very high unit pressure. Because the 45° and 7° angles give more support to the work, this impact is minimized and the rate of cut is lessened, and so is belt wear. One reason the 90° slotted wheel emphasizes belt wear is that the belt gets more flexing with the 90° serration. This results in the shedding of larger grains and faster shedding of working grains. Noise and chatter are other reasons why the 90° slot is seldom used. 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. The Serr-X Contact Wheel and Features The Serr-X is a special contact wheel developed by 3M for maximum conformability. The Serr-X rubber contact wheel has a wide range of benefits. Unlike a diamond pattern, the Serr-X does not transfer its pattern to the work. It conforms better, cuts faster, and also lengthens the life of the abrasive belt. Contact Wheel Performance This graph shows the results of a test using four different wheels . [. . . ] Atypical grade 100 aluminum oxide paper belt will produce a finish reading of about 90 when new . If it is moved at half-life, we have the effect of two different belts. 809-750-3000 Contact us on the Internet: http://www. mmm. c om / a b r asive s Distributed By: Important Notice: This brochure is intended to be an introductory summary of 3M products. [. . . ]