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blown air cylinder on small utillity hammer

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I recently had a couple tie rods break on my air cylinder, and of course the o rings went. Anyhow when taking it apart it became aparent that the tie rods were pretty good steel. I am guessing that I need to use 4140, 5160 or something
like that. Do I need to heat treat these as well? Has anyone replaced these with A36 and had that hold together? Thank you. Mark

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They broke where the nut screws on the rod, they were used for quite awhile, the hammer is about 12 yrs old. I am buying a new cylinder so the repair is only a temparary measure I have some 4140 on hand so I will be using it. I think I will try it without heat treating it and see if that works. I should have it together again tonight, so if it breaks instantly I will post otherwise who I will hope for the best.  

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Cylinder tie rods are normally a proprietary steel called "Stressproof" having a yeild strenght of about 140,000psi. They are usually roll threaded up from roll thread pitch diameter and are sized to not let the head or cap lift off the cylinder with normal pressures.

The idea is that an O-ring can extrude thru any given gap if the pressure is high enough, and on a low pressure air cylinder these pressures will ley an O-ring seal even a 0.005" gap


Ptree who in a previous century worked at a manufacturer of air cylinders

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