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?

As anyone who's welded aluminum knows, it doesn't glow, it just gets
liquid. You aren't going to get smoking blue chips flying like you do
with steel to clue you in as to the temp of the AL you're milling.
Uncomfortably warm is nothing on a metallurgical level. If it's hot
enough to sizzle water it may still not be truly too hot
metallurgically, but it could also be. I'd say painfully hot to touch is
when you should look for coolant options.