I'm trying to remove 8mm BMS axles from some aluminium parts and so far the only method which has yielded results is heating the aluminium parts with a butane torch for ten to fifteen seconds before attempting to remove the axle.
Is there any risk to the future strength of the aluminium parts by putting them through these heat cycles ? Is it likely to make them brittle in future or is the short term nature of the heating unlikely to have any lasting effect ?
Adrian.
It all depends on what temperature you take them to. Since aluminium has a greater expansion coefficient than steel, you don't have to heat just the aluminium. Can you put the whole thing in boiling water? Or an oven at say
200 C? You can get "crayons" which change colour at different temperatures if you know the temperature limit of the parts, which implies knowing what alloy and/or heat treatment they have. A hot air gun can be a bit more gentle than a gas torch. If you have one, you can use a non-contact (infra red) type thermometer to check what temperature your parts are reaching.
Boiling water is worth a try and you will get even heating through out the part. I've also used our domestic combination microwave, the convector oven goes up in 10C steps from 40 - 250, really useful workshop equipment when my wife's out...
Boiling them for several minutes has enabled me to free another three, so that's quite an improvement on my previous suscess rate.
I did break the remainder of my 12.9 bolts though, so the next step is to re tap them the M6 and try a bigger bolt. The strange thing is that the axles which have been removed are not that corroded, so the fit must have been tight to begin with, which is odd as they are supposed to rotate freely on these axles.
Adrian.
The boiling water seems to have helped, and at least I know to what temperature I'm heating it.
Not sure I've the guts to try our combi oven though - I get frowned at just cleaning Nitromors off stuff in the sink !!
Adrian.
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