I'll assume the holes are tapped through, not blind. There are distinct differences either way.
If you can find a name brand 2-flute spiral point machine tap or three, you shouldn't have to fight with it. Run fairly slow, like 50 to 100 RPM. This is slower than the SFM works out to but will give you better control. Drill slightly oversize if you can, giving you 50 to 60 percent thread. Studies show the loss in strength is negligible. Use a rigid clamped setup with positive alignment of the previously drilled hole to avoid flexing the tap. RapidTap cutting oil works well for me in this locale but any decent cutting oil should give similar results. Run the tap all the way through as far as you dare before reversing to push the chips out the bottom of the hole. Reversing before fully cutting off the chip can bind and break a machine tap, unlike a hand tap that's me and to reverse often.
Definitely avoid spiral flute taps unless machine tapping blind. They are the weakest of the lot.