A surface grinding machine is used to produce a smooth accurate finish on either metallic or nonmetallic materials. It uses a round rotating abrasive grinding wheel that remains stationary (but rotating) while the feed table (with work attached) is run in a reciprocating motion (left and right) under the grinding wheel. The specific amount of material to remove is determined by lightly touching off the work with the grinding wheel rotating and feeding the grinding head down a certain distance.
WARNING: If a grinding wheel is permitted to exceed the maximum safe speed, it may disintegrate and cause injury to the operator and damage to the grinding machine!
On a Manual Surface Grinder, you will then need to run the table left and right with one hand wheel while cross-feeding with the other hand wheel.
On an Automatic Surface Grinder, you will then be able to run the table left and right automatically while cross-feeding automatically. All you need to do is set the down feed and stroke.
Typically surface grinders can grind within .0001 – .0002 but not all surface grinders are created equal. The less expensive models may not hold up to tool room accuracies but could be used effectively to sharpen punches, and dies or do repair shop work. The more expensive models will use higher-quality spindle bearings and other components and will be better able to attain tool room accuracies.
To use the surface grinding machines, you must select the correct grinding wheel for the work to be ground. There are different wheels that are best suited for grinding:
- High-Speed Steel RC 50-68
- 400 Series Stainless
- Soft Steels RC 30-45
- 300 Series Stainless
- Cast Iron: Ductile & Gray
- Nonferrous Alloys
In each of the categories above you will need to determine wheel type by deciding if you need heavy (> .004), moderate (.002-.004), or light stock (.001) removal characteristics. Also, you will need to select a Grit size. 46 grit for general purpose, 60 grit for commercial finish, 80 grit for fine finish, and 120 grit for very fine finishes.
After selecting the correct wheel for your job, visually inspect the wheel for any damage or cracks. If no damage is found install the wheel on your surface grinder, tightening the left-hand spindle nut carefully with a spanner wrench. Make sure you replace the guard covering the wheel, put safety glasses on then turn the spindle on. Step away and let the spindle run for 1 minute to make sure the grinding wheel is running smoothly.
Once the grinding wheel has been dressed it is not recommended to turn the spindle off because turning off the spindle will require the wheel to be dressed again for some concentricity will be lost.
You are now ready to dress the wheel using a single-point diamond dressing tool that is placed and held down by the magnetic chuck. A small amount of grinding wheel should be dressed off of the diameter in order to make the wheel run concentric. Place the diamond dresser under the rotating wheel and bring down the grinding head carefully so it just touches the dresser. Sweep the diamond dresser across the rotating wheel using the cross feed (y-axis). Feed the grinding head down .002 then sweep the diamond dresser across the rotating wheel. Repeat until the grinding wheel face is clean and running concentric.
After the wheel is dressed and running concentric you will then be ready to gently touch off on the work (using the spark or layout fluid method). Next, set your “zero” on the down feed handle, raise the head slightly to clear work then the cross feed handle to distance the work from the grinding wheel. Next, feed the grinding head down a distance not more than .005. The amount of material being removed will determine how far you can feed the cross-feed per pass.
The benefits of surface grinding are:
- You can grind very hard or abrasive materials
- The high degree of dimensional accuracy
- Produces surface textures of very high finish
- Tooling is less expensive
- Work holding is easier because of the magnetic chuck
- Can be done automatically
In short, you will most likely need a surface grinder if you need to provide precision ground surfaces, either for a high surface finish or to attain critical dimensions.
Article Source: http://www.americanmachinetools.com/how_to_use_a_surface_grinder.htm