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Default 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

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Default 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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