Tapping Aluminum

I sense a disturbance in the force. A spiral TIP tap is for through holes, since it moves the chips forward. In a blind hole, this is a not-good thing. A spiral FLUTE tap, OTOH, is for blind holes, since it pulls the chip backwards.

Look at page 3: https://www.yamawa.com/en/support/catalog/pdf/understanding-the-basics-of-spiral-fluted-taps.pdf
Interesting that the MSC web page for that tap says it's for thru or blind holes. Anyway, I tested it on a thru hole and noted that it was pushing the chips through the bottom of the hole. So, for this particular work-piece, thru holes were fine, so I drilled them through and then tapped. It worked great btw.
 
I don't think I'd be running my taps that fast. Of course I'd just set up my tapping head in my drill press with a depth stop. With aluminum I'd be using a fast spiral tap . Kero or wd40 for cutting fluid. May not be CNC but they work great.
 
Wawoodman is correct. I do a LOT of blind holes so spiral to me is lifting the metal up out of the hole. I'm sorry! After about 50 years of doing this stuff you can get a bit sloppy on correct names to use. I have 2 tapping heads and they don't get used much as I do 8-24 and up under power at 100rpm. Never a problem with thru holes and for blind I pay attention to the DRO so I don't bottom out. It works for me but maybe a bit harry for the younger guys.
 
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