In article ,
CW wrote:

"Markem" wrote in message
.. .
On Sat, 30 Jan 2010 11:58:23 -0600, dpb wrote:

Markem wrote:
...

Beware of chromed tools and titanium do not play well together. ...

In what way?

Degraded the titanium is what we peons on the flight line were told.
Maybe aircraft grade problem, do not know, ya do as told generally in
the military.


I'm wondering if anybody really knows (and whether it really makes any
difference). Some years ago, I was working in a shop that was making a laser
for the military, the body of which was titanium. We were not to allow any
steel to come in contact with the titanium. All cutters were carbide, vise
jaws made from aluminum, deburr files were diamond and the parts were not
even set on a steel worktable. They claimed degradation of the titanium. I
have machined lots of titanium for commercial aircraft and no such
precautions were taken (or specified by the buyer). I wonder what the
military knows that Boeing doesn't. Hard to believe it's much.


Titanium exposed to minute concentrations of certain other metals becomes
=very= hard and *BRITTLE*. All well and good if the entire piece is treated
uniformly, but can cause all sorts of problems if it is a 'spot' treatment.

This is a characteristic of 'nearly pure' titanium, that is not shared by
most titanium compounds.

Some of the metals that cause this behavior in microscopic quantities, applied
to the surface, can be used in macroscopic quantities -- making titanium
alloys -- that do not have the same characteristics.

IIRC, skin panels for "Blackbird" were 'unrepairable' for this reason -- complete
replace of an entire panel necessary.