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I keep my speeds down on my mill to avoid overshoot on spindle reversal. On smallish taps 300-400 rpm max (for my biggish 7.5hp servo spindle) on both my lathe and mill. I assume you can go much faster. The big key is to use quality taps of the right shape.

Through Hole = Spiral Point Tap
Blind Hole = Spiral Flute Tap

I love the elektraLUBE coating on the OSG taps I get from MSC. For smaller holes like 4-40 thread forming taps shine with no chips to fill the hole or to clean out. I rarely rigid tap below 1/4-20 on my machines but if I did I would go with thread forming taps for smallish holes.

On my lathe I have a ngcgui subroutine for rigid tapping and just fill in the blanks and hit go...

John

waynegramlich wrote:

Does anybody know if there is a recommended speed for tapping aluminum for various common diameters and thread pitches -- 4-40, 6-32, 10-32, etc? I suspect that aluminum tapping speeds are faster than most.



-Wayne[/quote]
I answered this before but pushed the wrong button and lost the message.
I do 2-56 up to 6-32 holes in aluminum alloy at 1000 RPM, and 10-32 at
600 RPM. I use spiral flute taps for thin material, and spiral point for
deeper holes. Note that the manufacturer specifies something like
3X hole diameter for the safe depth for the spiral FLUTE taps. I think
you can go a bit deeper, but the flutes eventually clog if you go too
deep. I use combo drill-taps a lot, so I effectively spot, drill through and
tap with one tool. I have a program that takes in a file of XY coordinates
and generates the G-code for that operation.

I use alum-tap as the tapping fluid of choice, it works amazingly well for
tapping aluminum. I often get thousands of holes in sheet aluminum
out of one tap.

Jon

jmelson wrote:I answered this before but pushed the wrong button and lost the message.
I do 2-56 up to 6-32 holes in aluminum alloy at 1000 RPM, and 10-32 at
600 RPM. I use spiral flute taps for thin material, and spiral point for
deeper holes. Note that the manufacturer specifies something like
3X hole diameter for the safe depth for the spiral FLUTE taps. I think
you can go a bit deeper, but the flutes eventually clog if you go too
deep. I use combo drill-taps a lot, so I effectively spot, drill through and
tap with one tool. I have a program that takes in a file of XY coordinates
and generates the G-code for that operation.

I use alum-tap as the tapping fluid of choice, it works amazingly well for
tapping aluminum. I often get thousands of holes in sheet aluminum
out of one tap.

Jon[/quote]

Jon:

Thanks for the great info. That is exactly the kind of information I needed.

Again, thanks,
-Wayne