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Table Of Contents: 1. Grain Types 2. Grit Sizes |
7. Importance of "Set" Numbers 8. General Def./ GWI Marking System 9. Chuck Repair 10. Loading 12. Work Speed |
14. Friability 17. 18. |
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7. Importance of "Set" Numbers (11-03-2005) Fact & Question: Other chuck styles have set numbers similar to the Cortland series. Is the set number important on those styles i.e. Norton or Sterling?
Answer: Yes and no, and that is why it sometimes is confusing. A popular NO segment size is a NO-18. The size of both an NO-18 and NO-22 is the same (5 x 1-1/2 x 6). The only difference between the two is the number of segments in the set. Since customers generally know how many they want we do not ask for any additional information. 8. General Definition of the GWI Marking System (11-17-2005) Fact & Question: All grinding wheels have material specifications that are a part of any size wheel. The GWI (Grinding Wheel Institute) established a standard marking system that has long been recognized by consumer and manufacturers alike. It is a standard of markings only, not a standard of grinding action. What is the purpose of the marking system and can it help me determine the difference between manufacturers?
Answer: The distinction between the markings of a particular segment and it grinding action should always be kept in mind. While much good can be accomplished by an understanding of the marking system, it is only a beginning in the understanding of a wheels specification. About the only thing consistent between manufacturers that use the system is the uniformity of the markings, or more specific the location within the formula of grain type, grit, harness, density and bond. |
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9. Chuck Repair (1-23-2006) Fact & Question: The chucks on vertical spindle grinders are an integral part of successful and accurate grinding. Many times problems of cracking segment stones or chatter marks on ground parts can be traced to sloppy fitted segments in the chuck. Can the chuck on my machine be repaired or replaced.
Answer: There are a few companies that still sell repair parts for common chucks. Cortland chucks are the easiest to repair, and obtain new. Many times it is more economical to replace an obsolete chuck with a new Cortland. Systec may be able to help you with some of these issues. The best way is to call us to discuss your individual needs. |
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Fact & Question: One of the most commonly discussed problems in segmental grinding is loading. Loading if where metal lodges in the wheel pores. What causes loading and what can I do to eliminate it?
Answer: There are several causes for loading and all of these can generally be controlled with a little thought and care. The most obvious occurrence of loading happens with too fine of a grit. The obvious answer is to use a coarser grit which will also increase the aggressiveness of the segment. Sometimes a segment that is too hard will be the cause and by stepping down a half or full grade you will alleviate the problem. Poor coolant flow or dirty coolant which contains too many particles, called swarf, can cause the problem and that is easily solved by increasing the coolant supply at the nozzle or cleaning the coolant and tank. |
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11. Toughness versus Hardness (3-20-06) Fact & Question: One misconception that seems to be prevalent is the miss-understanding between the terms hardness and toughness. Understanding how a wheel grinds (cuts) and how long it last (wears) is a balance that we struggle with constantly in balancing the issues of wear versus cutting action. What is the difference between hardness and toughness as it pertains to a segment? Answer: Very simply stated, toughness is a grain issue; hardness deals with the amount of bond that goes into the wheel at manufacturing to give it strength during the grinding process so that its breakdown is economical. Once that is understood the deciding factors in manufacturing a segment relate to the horsepower of the machine and the hardness of the part being ground. While this is a simplification and somewhat understated the simplicity of this is that more horsepower allows the segment to be made harder so that it doesn’t wear quickly. Tougher grains work on very hard materials. This leads into areas of the newer tough grains like ceramics and when to use them. It is always a challenge to balance the grain to the hardness predicated on what is being ground. |
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Fact and Question: Work speed is always an issue in grinding. There is a different set of “rules” for horizontal spindle grinding (surface grinding) than there is for rotary table (segmental) grinding. What is the rule of thumb for work speed for segmental grinding?
Answer: Generally speaking with surface grinding if the work speed is increased and all other movements are kept constant the wheel with act softer. If the work speed is decreased and all other movements are kept constant the wheel will act harder. With segmental grinding increased rotational speed, everything else being constant, results in less work per revolution and therefore a harder action. Therefore for a wheel of given grit, grade, bond and structure, it is necessary to determine the proper relationship between work speeds and the wheel for the most efficient grinding action. When changes are made in wheel specifications, a new relationship needs to be re-established between those criteria to maintain grinding efficiency. |
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