Document ev8YMX4nkB8OyXaYdGe26qkyp

SO Metals Industry Tip No. 2 Tip Xo. 2 can be helpful in classifying a pneumatic tool problem. In descaling a roll the operation is done very much in the same fashion as one would descale sled plate or nick concrete. Three years ago this opera tion was quite hazardous because of poten tial accidents associated with the breakage of chisels. Lacerated nr broken fingers were common because of the inevitable exposure of a mans hand when an end of a chisel broke off. To understand the fundamental* undcrlying this failure, tve measured from the origin of the failure to the end of the chisel as recommended by the suggestion for an alyzing failures. Results of measuring 360 such failures produced a fretpiency distribu tion which told us immediately that the fail ures did not occur at :!ie same sjot. They varied over a two-inch length. Tit Xo. 2 suggests that this is a metallurgical proln lem. Therefore, we investigated the factors that we thought were related to this failure. We learned tliat each chisel was subjected to bending stresses due to off-center impact and these bending stresses started failure in the surface layers. The exact location of each failure was dictated by mimite irregu larities in the surface. Each chisel had on its surface an unavoidable layer called a decarburized layer and it is a recognized fact that decarburization does not resist repeated stress as well as material not decarlmrized. We were faced with the problem of either removing the decarlmrized layer or strength ening it. W'c derided tliat strengthening it would be the most practical and we chose to try shot pecning the surface of the chisel* By this method, the surface of the chisel is sprayed with the steel shot which closes up any pits in the surface and induces favor able compressive stresses in the decarlmrized layer. Our first tests were conducted on a lot of 1.000 chisels. One-half of the lot was the so-called standard chisels that served as a control group tliat would give us an accu rate picture of the performance of unpeened chisels. The remaining ltalf of the lot was shot peened to strengthen the surface layers. With 500 standard chisels after 14 days service, there were 360 potential accidents, with 360 broken chisels and 140 dulled ones. With 500 shot peened chisels after 39 days service, there were only 10 potential acci dents with 10 broken chisels. 13 broke: through the stamp mark, and 477 dull or.ts While this was an encouraging improve ment, we did not stop development work. We learned that by revising our peenir.^ technique slightly, we could reduce the 1-ty doll chisels in the standard chisel pile to 2. Our records show that potential acridemhave dropped from about 300 per 1.000 mir. hours to less than 1 per 1.000 man hours Broken Gouges Tire same reduction in potential accidentwas reproduced in another tool known tire gouge. The origin of failure varied con siderably as was indicated by the length <: the broken lips. Tit Xo. 2 provides the clc as it did in the case of the chisels and. i:: this instance, too. hundreds of potential ;..* rident* have !cen eliminated by shoi peenir.. the gouge*. Stripper Tongs As with the preceding cases of failure >: jcicumatic tools, the same techniques arc ap plied to analyzing failures in heavy' equip ment. A device used to remove ingots fr*':-. their molds is known as a stripping tons: Our records slww that many of the*c tong* liave spread or lave broken suddenly in tk< past. Fortunately, we did not have any ac cidents; but no one could guarantee immu nity under the circumstances with whirl they were used. In examining the failure*' in accordance with the suggestion advanced, we learned that the origin of failure varied widely. Some failures were near the lower ends, some were near the pins, and some were midway between the pins and the end* Tit Xo. 2 suggested a material investiga tion. W'c investigated the stresses tliat could lie set up m the tongs under various toad*, jiarticularly when sticker ingots were beinc removed. We learned that the materia: should be considerably stronger to with stand normal operation. We immediate!) clianged the material specifications from an nealed plain carbon steel to heat treated alloy steel and almost overnight improve ment was noted. Instead of spreading at the gripping sur faces. the new tongs resist spread. But. more important, is the elimination of breakage In over two years of service tlrere lias n*: Ireen a ease of potential accident. There Is a Man in the House 37 Axle Failures Axle failures on rolling stock constitute one of the most serious potential accidents we have to deal with. When an axle breaks, r.o one can predict final consequences. Forv.matcly. we have never had a lost time accident due to such futures but we did have a potential as high as 12 in one year. As many as 12 broken journals, off cars ccurrcd in one year. They were all at the qnie location, the radius at the end of the bmrnal. Ttf Xo. I suggested a design problem. W'e studied the design and learned that :he l/i inch radius at the end of the journal was a stress raiser and it actually increased -tresses by nearly 2 times. The responsible :actor was obvious to us as investigators, hut we felt that we needed visual proof to support our theories. It occurred to us that it the theory was correct, then both ends of the axle were exposed to the same stress levels and. although it appeared that only one journal was broken off. the "unbroken end" should be cracked. To prove this point, we examined the "unbroken" journal and saw nothing. Realiz ing that cracks of this nature are too tight :o see with the naked eye. we wrapped an ordinary welding lead around the "unbroken" imirnal and passed current through the lead. This magnetized the axle and after sprin kling magnetic power on the journal we brought oat the clinching evidence. Here was proof that the potential accidents were originating in tire radius. We redesigned the axles and after three and one-half years of service, not a single failure has been reported. Shear Knife Breakages Shear knife breakages are one of the worst kinds of potential accidents because of the possibility of flying pieces of steel. All of the knives were in operation cutting steel 1reams. Some of the knives were spalied and some were broken. When the knives are examined carefully, the origin of failure is found at a different location, thus indicating a metallurgical problem. A careful study of this problem showed that high frictional heat was being devel oped during cutting operations and caused tiny heat check? to open upon the suriace and finally leading to these serious potential accidents. By changing the analysis of the material to provide heat resistance we have completely wiped out these failures provid ing safer operating conditions for the shear men. If we have improper balance of material, design, and load, we can expect unpleasant consequences, including potential accidents. By applying Tit So. 1. or. Tit So. 2, we have shown how it is possible to achieve proper balance of material, design, and lead, and bring about several pleasant consequence*, including reduced potential accident*. There Is a Man in the House By M. BRUCE GORDON Supvr^ Employee Services. Industrial Re ations Dept. Engine and Foundry Div., Ford Motor Co.. Dearborn, Mich. My discussion is the story of supervisory *afetv training in the Engine and Foundry Division of the Ford Motor Company. Before we get into the details of tliat pro gram you might like to know something about our division and its relation to the overall company operation. The engine and foundry division is pri marily responsible for the manufacture of all automotive engines used in the company** jassnger and commercial vehicles. This includes the Lincoln. Mercury and Ford overhead-valve \'S engines and the Ford "6" overhead-valve in-line engine. We also build a complete line of industrial engines as well as a lank engine for the Armed Service*. W'e have eight operating plants, four of which are foundry operations and the re maining four are engine machining and as<*mhlv plants. Our employment approxi mates 33.000 employees at the present time with a very wide range of job cla**itica- tions.