Early in the piece I acquired a few impact screw drivers from the flea, most contained in their original tin boxes with two slotted screw driver blades (large and small) two Phillips blades (large and small), their original instructions and bearing little signs of use.

They appeared to tell the tale of something which seemed to be a good idea at the time. Back then I sometimes had the unsettling experience, when, rarely, an impact driver's blade correctly fitted a slotted screw, of neatly twisting the top from the shank of the screw.

Sometimes they worked correctly but the stubby blade attachments made them difficult to grind to correct size and I believe that if a screw is frozen in place only to the extent that an impact driver will release it if the correctly sized blade is available then it can be much more carefully removed by jarring it and then using a brace with a four-jawed chuck and a correctly fitting blade chosen from the almost infinite variety of sizes designed for use with electrically powered drivers.

On the other hand, I never pass up a $0.50 or $1.00 Turner or Stanley slotted-screw driver at the flea as there always seems to be yet another screw requiring a blade to be ground to fit it whilst it does not require the application of force engendered by the use of a brace.

Some machine screws are beyond redemption because they have been jump-threaded or wedged somehow or other, perhaps by over-enthusiastic jarring, maybe with an impact driver.  Sometimes they have bottomed out and been upset within the hole by jarring attempts, providing another impossible extraction problem. In these cases, where Easy-Outs create more problems than they solve and work, when they work at all, only on correctly set screws, they simply have to be bored out and the hole has to be re-reamed and re-threaded and fitted with a screw of the appropriately larger size or filled and re-bored etc.

It is only when jarring followed by a careful and controlled attempt with a brace to remove a screw fails that the freezing and heating technique, followed by jarring, is applied.  And it seems to work - with the reported exceptional cases, of course, experienced by those persons who abide in latitudes where the laws of physics have been repealed.

I might add that it has never occurred to me to use an impact driver on a plane, or any other tool for that matter.  Perhaps it is because I have yet to acquire a tool with the intention of destroying it.

Regards from Brisbane,
John Manners