Page History: Tips, tricks and a little PM (Pure magic)
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Page Revision: 2009/01/25 14:32
Here are some tips and tricks that have been collected through years of machine maintenance and repairs.
Stuck inner cup.
Every now and then I come across a tapered roller bearing cup that is stuck in the bore. Heating the casting is not advisable as it can warp, or it is just too big to heat. Anyway, to get the cup out, have your welder run a bead around the inside of the cup equidistant to each end. This will cause the cup to shrink....a lot. When it cools, the cup will fall out.
Never assume anything with regards to the amount of shrinkage or expansion an item has. Calculate it. You might be surprised at how much expansion or contraction you have available. Don't forget that different materials has different expansion rates and that can make a difference between making two objects bound tighter or looser when heated.
Electric issues
The handiest tool to have is a clamp on ammeter. You cannot troubleshoot some things with it it. An electric water heater is one example. You can measure voltages and even resistance but both of those can be foolers as a element that has gone open more than likely will also be exposed to the water which will shows reasonable close resistance values. The only way to determine if an element is working is if it draws that proper amount of current at the proper time.
Two handy formulas:
Watts
--
Amps X Volts
E (volts)
------
I (current) * R (resistance)
Cover up what you don't know and you have the formula.
For example, we have a 100 watt light bulb and want to know how much resistance it has.
We know that it operates at 120 volts so....
We take the first formula and determine that we have divide 100 by 120 to find out how much current it draws. That leaves us with .83 amps.
Next we take the next formula and determine that we take 120 and divide that by .83 amps. That leaves us with 144 ohms. That is what you should measure using an ohmmeter.
Rusted or "frozen" bolts
Sometimes penetrating oil works and other times it is pointless. It depends on what is rusted and where it is rusted. There is no magic "bolt remover in a can". It does not exist contrary to what anyone tells you.
Sometimes the best way to remove something stuck is to tighten it first.
If a bolt or nut is stuck and the impact wrench wont break it loose in a few seconds, STOP. Go get a ratchet, socket and a piece of pipe if needed. All you will accomplish by letting the impact hammer on it is to wear out the bolt head, socket, and impact.
Propane torches are OK for heating larger items, but if you want to head something like a nut, get a small acetylene torch. You will have a pinpoint flame that is about 3 times hotter than propane. The goal here is to get in there, get the nut hot and get out without heating up the bolt or surrounding area too much.