Need some tapping advice

[mdred68]

I have a tormach pcnc 1100 and i want to start tapping with it. I have a job that needs 7 4-40 blind holes tapped in 6061 Al. I dont know if i should use a spiral flute or a roll form tap and how fast should i run it i know that the feed will depend on my speed. Also, i have to tap some 2-56 blind holes in delrin and i have the same questions as tapping the bigger holes( type of tap and speed). If anyone out there has any advice i would be grateful. I would like to save some tooling and scrap cost. Thanks

[kevinro]

I guess a key question is do you have a tapping head? I have the Tension/Compression Tapping Head Kit (31807) and it seems to work quite nicely. There is some math to be considered based on the speed of your spindle (which should be fairly slow!). You should definitely check out the videos on how to tap holes.

I have been using spiral taps. You are likely to get several opinions on roll vs forming. I have done both. For me, spiral taps work just fine.

Go back a few weeks in this forum, you will find this is a common question and we have hashed through it at least twice since June.