need more advice on rigid tapping

[jeremyinnys]

i'm rigid tapping a 7/16-20 form tap. (that's what customer wants) we've been drilling parts on vmc, then 2nd op tapping on our small hardinge lathe. well i gotta start tapping them on the vmc. i've done some, but it's way too slow. i've tried 100-140 rpm's at feed of .05(thread lead). i gotta tap 1.5" deep, 20 parts per cycle. any help i would greatly appreciate. i'll check back tommorrow. thanks! or maybe faster not rigid tapping?

[matsuura]

i'm rigid tapping 1/2-13 in alu. 1833rpm 141ipm 1'' depp

[psychomill]

1-1/2" deep on a 7/16-20... wow. You can go faster but you didn't say what material you're cutting. If you're cutting aluminum, you can go way faster. Just make sure you've got gobs of coolant running... and maybe a coated tap (since you have so many holes to do thats pretty deep). Peck tapping can help too if you have problems.

Another option... CNC tapping head like from Tapmatic. Program it like a bore cycle (or long hand... depends on the tapping head and thread). No spindle reversing...

[hoss64]

One thing that will help is a fast spiral tap. The cutting edges on the flutes are staggered, and the chip will eject throught the top of the hole. Reiff & Nestor makes a pretty good one. I was tapping through holes with at 1/2-13 tap at 300 to 400 rpms at over one inch deep. You can find these taps in MSC Industrial Supply Catalog.

[hoss64]

Material was cold roll steel plates.

[lerman]

Originally Posted by hoss64 One thing that will help is a fast spiral tap. The cutting edges on the flutes are staggered, and the chip will eject throught the top of the hole. Reiff & Nestor makes a pretty good one. I was tapping through holes with at 1/2-13 tap at 300 to 400 rpms at over one inch deep. You can find these taps in MSC Industrial Supply Catalog.

jeremyinnys said he's using a form tap. That means there are no chips to eject, and solves one problem.

psychomill -- he doesn't want gobs of coolant. Form taps require lubricant; not coolant.

Ken

[jeremyinnys]

material is 1018 i think, or similar. customer ships us the blanks. thanks again.