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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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1977 Ford F250 sector shaft spray welding
oldjag wrote:
My 1977 Ford F250 power steering box is a bit loose on the bottom sector shaft journal. This was a $350.00 "rebuilt box" but it looks like the only thing rebuilt about it was a resealing job. I opened it up and the main issue seems to be the lower end of the sector shaft, (nominal 1.375 dia), is worn about 0.003" and the housing bore is ovaled out about 0.015". The sector shaft on this box has no bottom bushing or needle bearing. I'm thinking about boring the housing for a Torrington needle bearing. The sector shafts are no longer available, so it will need to be repaired. I've got a similar issue with my power hacksaw. On the cutting stroke it makes a "bonk" noise (only when actually cutting; the machine is almost silent when running without cutting). I took everything apart. The only cause I can find is 0.027" clearance between the bronze bush in the final pulley (which also acts as a flywheel and crankshaft) and the supporting shaft (the figure is the total, i.e., the sum of the wear on the bush and shaft diameters). The shaft has a nominal diameter of 1.250". The wear is almost all in the direction of the belt pull, which is perpendicular to the motion of the hacksaw bow. I was surprised to find that 0.027 was enough wear to make a loud noise when the pulley only turns at 100 or 150 rpm (the machine has two speeds). Unless there's another cause for the noise, but I can't find it. Most of the wear (0.024") is on the shaft. The bush has much less (0.003"). I imagine the bush has been replaced many times. So there's little point replacing the bush. The shaft is no longer available as a spare part, and would be hard to make as it has oil channels through the centre. So one option would be to build up the shaft somehow (not something I'm thinking of doing myself). There's a little scoring on the shaft. I considered trying to polish out the scoring, but I'm not sure how. As the machine works fine, I'm inclined to ignore the bonking noise. I don't want to do more harm than good. By strange coincidence I found a Eutectic Rototec spray welder kit new in the box on Craigs list today. It came with with a supply of unopened spray powders. It's more or less a oxygen/acetylene torch with a feed hopper and a tool post mount setup for for spray welding. According to the manual, the Rototec process is a "cold" process that does not heat the shaft over 500 F, I'm thinking about using it to build up the worn journal area on the shaft. One of the powder formulations is recommended for build up of bearing races, so it sounds possible. The other alternative is bushing the housing with a bronze bushing. This would have lower unit loading than a needle bearing on the shaft overlay. Do you mean that the centre of the shaft doesn't get hotter than 500 F? Surely the surface has to get hot enough to melt the steel? Best wishes, Chris |
#2
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1977 Ford F250 sector shaft spray welding
Do you mean that the centre of the shaft doesn't get hotter than 500 F? Surely the surface has to get hot enough to melt the steel? Best wishes, Chris Actually not, as Grumpy mentions Eutectic provides a 200F and a 500F surface marking crayon for the shaft to be repaired. The procedure calls for maintaining the surface temp between 200 and 500 F. A bond coat is used first, then one of several top coating alloys. They refer to it as a cold process. Some of the powders are exothermic according to the literature, but the base metal does not get very hot. |
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