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Unregistered
Join Date: Aug 2000
Location: a wretched hive of scum and villainy
Posts: 55,652
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I have a spreadsheet at work that calculates the % of yield on different fasteners based on toque and friction factor.
The difference between dry and lightly oiled with machine oil is huge.
It takes almost twice as much torque to reach the same % of yield with dry threads.
But ..... if there was oil on the threads and it had a little time to soak in, consider them oiled.
Even if the majority of the oil was wiped away or pressed away or whatever, it's still there and working. It gets into the pores and that's where it does the work.
Here's an interesting study we did one time:
We took two identical centrifugal pumps driven by 40 hp motors. we assembled one pump with new SKF ball bearings with no lubrication whatsoever except the preservation film they were shipped with.
IIRC the radial bearings were 6310 C3 and the thrust were 7310 BECBM.
We assembled the other pump but soaked the new bearings in shell turbo 32 mineral oil for about 10 minutes prior to assembly.
We started both pumps under load with no lubrication.
The pump with the bearings we soaked in oil ran for over 24 hours but was obviously eating itself up by that time.
The other pump lasted less than an hour before vibration levels exceeded safe limits (approx .8 ips).
Most of the pumps at that plant ran on nothing but a very fine mist of oil that was barely visible.
And that's all they needed.
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