[graemeian]

I need to CNC tap 1/4-20 threads through a .75" mic-6 plate. I plan to use a spiral point tap with flood coolant. I usually run at 800 rpm because the numbers are easy to remember. I looked at form tapping but I am afraid it may crown around the hole.
Form tapping is easiest as there are no chips. Any suggestions and please include RPM. Any special coating Thank you.

[metalmayhem]

I'm all for form taps but on mic6 I prefer spiral cutting taps 800-1000rpm is reasonable . osg make decent taps emuge makes exceptional taps

[graemeian]

Thank you.
In through hole using spiral taps, I will sometimes tap in sections. Such as... drill through part. Tap half. Run drill back through very fast or stop M1 and visually check. Tap the remaining half. Am I being too cautious?

[metalmayhem]

correct me if I'm wrong but I'm picturing a fixture plate . Sometimes better safe than sorry so I'd say tap at 2 even 3 depths then be done with it . Thats as long as your spindle holds orientation

[graemeian]

Thank you very much. Just purchased new taps.

[BRAIN-HURTS]

It sounds very much to me that you should look into thread milling and thread the holes in one go.