Tapping 303 Stainless

[Crashmaster]

'Lo guys.

I am tapping a Letter 'F' sized hole in 303 stainless on a CNC lathe with a 5/16-18 tap. I am using an OSG Spiral Flute, steam oxide bottoming tap. The tap seems to be holding up fine but I am always on the look out to do better than fine. These tap's cost 14-16 USD and I don't mind spending more if the tool life increases. Just wondering what success you have all had with tapping 303 stainless. Which taps work for you, which taps make your head hurt. Thanks in advance!

Joe

[djr76]

I tap 1/4-20 and 5/16-18 holes in 303 everyday at my job. I specifically use the OSG Exotap VA3 taps designed for stainless. They pretty much outperformed any previous tap I ever used and have been using them for about 8 years i think. Run it at 20-30 SFM using this formula RPM = SFM X 3.82 / Tap Diameter

[Crashmaster]

OSG taps seem to be pretty consistent. Do you know about how many holes do you get per tap?

[neilw20]

I've had good success with intermediated 'Blue Point' Gun Tap from Goliath.
Due to the grind, the chip comes out curly AHEAD of the tap. None gets in the flutes. These have been 3 and 4mm blind holes about 1/2" deep. One pass.
Goliath recomended using intermediate, and I have not looked back since.
Very good tool life. Can't remember the name of the magic tapping fluid used.

[djr76]

Not of the top of my head Crashmaster, but anything over 1/4 is pretty robust and free cutting and I get alot of holes out of 1 tap.

[laka]

Most every tapping job we need to do in stainless (304 / 316) we use forming taps. they work great, no chips and you can spin them twice as fast as cutting taps.

[djr76]

Originally Posted by laka Most every tapping job we need to do in stainless (304 / 316) we use forming taps. they work great, no chips and you can spin them twice as fast as cutting taps.

Mine too, I work for an OEM food processing equipment, its all mostly 303/304 stainless, some 440C and 17-4 ph.