Multiple tapped holes on NC, tapping fluid, or is coolant ok?

[Brian FRF]

Got a few parts being run, several tapped holes, 3/8, fine thread. Currently using a 3 flute cut tap, spiral point. some are 1/2" deep, into a .800 deep hole (finish tap done by hand) and some are through, 1" thick part. 2 parts, 15 holes per part, so 30 per green button push.

Question is, working in mild steel. Currently going to the machine, and putting tapping fluid in each hole, and periodically on the tap. Id prefer to not do this, but I dont know that the coolant we use would be adequate to lubricate on its own. It a water soluable oil. Or maybe the coolant alone would be OK, if we went to using form taps?

What's everyone doing for this kind of thing now?

[sti2011]

Form tapping would be your best bet then you could do the holes complete without having to finish them to depth after. And coolant should be more than sufficient in mild steel. May want to blow the holes out before you tap though, to make sure there are no chips in the holes. I also on occasion use straight unmixed coolant as tap lube. It cleans off the part relatively readily as the part finishes up in the cycle.......

[Geof]

Coolant is fine, just increase the concentration to about 10%.

You should be using a spiral flute tap on the blind holes; with this you can easily tap to 0.5" in a 0.8" deep hole.

Will your machine do rigig tapping and peck tapping? Going through 1" in a single shot may be a bit much, I would probably do it in three pecks.

[sieza]

Like some other bloggers said coolant should be ok, use a spiral flute tap, It also depends on the tap that you are using. Some taps last longer than others, I like to use OSG and EMUGE.

[Brian FRF]

The .800 deep holes get hand tapped with a bottoming, spiral flute by hand, to get .750 + of thread. I have no plans to try and finish tap on the machine, especially since its older, so it doesnt do rigid tapping.

Ill try increasing the coolant concentration, and go for it, sound good to me!