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Applying stellite to the cutting edge Dredge Bit Is Protected With Stellite OR certain types of digging, the modern suction dredge is unsur- passed. It is continuous in opera- tion and will handle tremendous vol- umes of sand, gravel, mud and clay. Many, of these materials are highly abrasive, and all parts of the han- dling machinery therefore, are rapidly worn away. The action is particular- ly severe on the blades of the rotary cutter which usually is a steel cast- ing having five or six spiral blades, extending from an annular base and terminating in a heavy central sec- tion attached to the driveshaft. The driveshaft with cutter in place is sup- ported on a heavy ladder. Mounted on the underside of °* the ladder is a suction pipe, extending beyond the end of the frame into the driveshaft and the cutter. As the cutter loosens the dirt, it is drawn into the suction pipe by a powerful centrifugal pump, and then forced out through the discharge pipe to the point of disposal. Recently a dredge was sent to a South American harbor where it was known that the digging was.such that . the life of the rotary cutter would be From an article appearing in the March issue of Oxy-Acetylene Tips. 30 only about six weeks. This cutter was a steel casting about 4 feet in diameter and 4 feet long, weighing about 3500 pounds and worth $800 f.o.b. the American foundry, the ques- tion of a duplicate arose. Each of the six cutter blades were about 12 inches wide, the cutting edge being %-inch thick, increasing to about 1 inch at the rear end. Use wears the blades down until 4 or 5 inches wide, when replacement is necessary. In view of the expense of the cut- ter, and the possible delays in de- livery, it was proposed to protect the cutting edges with stellite, an alloy having exceptional wear-resisting properties and suited to such _ use. MARINE REVIEW—July, 1927 _ panying For this purpose a band of stellite about 4 inches wide and 25 inches long was to be applied along the in- side and outside faces of the cutting edge of each blade. The stelliting process is based on the fact that the alloy melts at a lower temperature than steel and adheres’ tenaciously when properly applied. It is used in the form of welding rod and an oxyacetylene blowpipe furnishes the heat necessary to apply the alloy. As will be evident from the accom- illustrations, welding was The cutter is protected inside as well as out from abrasive action of sand and gravel complicated to a certain extent by the curvature of the blades, which made it necessary to change the posi- tion of the cutter at brief intervals. The stellite coating was x to %- inch thick, 150 pounds of the alloy being required for the six blades. The casting was rough and _ had_ been painted, all of which tended to im- pede the operation. It therefore took about 105 hours to complete the job. This protecting layer brought the total cost of the cutter up to $1700, a little more than twice the cost of the unprotected casting, but judging from similar applications, the life of the cutter should be increased many times, so the extra investment is more than justified. :