On Thu, 11 May 2017 15:55:40 +0200, Emanuel Berg
wrote:

Often the situation is like this. There is
a very rusty bolt with a Phillips head.
However when you rotate the nut the bolt
rotates as well. And to hold it with
a screwdriver just destroys the star pattern.
To hold it with a pair of pliers isn't possible
either as the whole thing just rotates in the
grip working off the rusty layer.
Spraying WD-50/5-56 to no avail. I would like
to replace those with M5x16s. So far I have
drilled right thru the bolt and nut to dispose
that way. Is this what you usually do?

No. What I do depends on the situation. On the shopping list of bolt
extraction methods a
- Drill it out.
- Drill and screw extractor.
- Nut splitter.
- Grind off the head with a die grinder or Dremel tool.
- Cut a slot with a Dremel cutoff disc.
- Chemical attack.
- PB Blaster.
- Reverse current electrolysis in 15% sulfuric acid. This eats
steel but leaves aluminum intact.
- Boil in alum (hydrated potassium aluminium sulfate) and water.
- Propane torch to expand the steel and loosen the rust line.
- Penetrating solvent (50/50 acetone and ATF).
- Ultrasonic scaler to break loose the rust.
- Cutting torch to remove nut or head.
- Long cheater bar and impact socket until it breaks.
- Beat on it with a hammer until it breaks.

I've used all of these at one time or other with the usual variations
in results. Much depends on the condition of the bolt, access to the
bolt, what needs to be preserved, time, where the work is being done,
value, etc. In the past, I favored the various brute force methods
resulting in breaking the bolt. Acetone and ATF seems to work as well
or better and has is currently my favorite method.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558