Doug Miller wrote:
In article i6Zzi.2449$Pd4.2008@edtnps82, Trevor Jones wrote:


Whatever you do, try to keep the stock from heating up. Hot aluminum
becomes soft aluminum. Sorta like machining warm chewing gum. Ewww!


How hot is too hot? Not looking for a specific temperature here, but general
guidelines -- obviously a dull red glow would fit in the "too hot" category,
but where does "too hot" begin on a scale like warm to the touch,
uncomfortably warm, painfully hot to the touch, sizzles when water dripped on
it, etc?

Chips go dead soft, part builds up heat. Uncomfortable warm. That kind
of range.

You know you are too hot when the chips start to bung up the flutes, eh!
Watching the behavior of the material while it is being cut is a
pretty good indicator. If it starts to smear, it's definately too hot,
the tool is too dull, or both.

For the most part, too hot to touch the part, right after a cut, is
way too hot, IMO. It's a good place to start, for me, anyways.

I think you would have a puddle, if you got a dull red.:-)

I like coolant, if I can use it. The mess is often worth it, for the
easier machining, and finish.

For annealing aluminum, I have used a sharpie marker, and heated until
the line dissapeared. That leaves the area dead soft. It will naturally
age harden to about a -T3 temper in a few weeks. In a general sense, anyway.

The specific heat treat schedules for specific alloys have to be
followed if you want exact type results.


Cheers
Trevor Jones