[Asheen]

I need to tap 2000 m8 and m6 holes in stainless steel on my cnc lathe. I am using G32 tapping cycle. It is the code that mastercam generated. I have tried FEW blue band spiral flute taps. the tap broke after 20 holes. I tried Guhring blue band spiral point. It broke after 2 holes. I have a Emuge tap and a OSG tap. but now im scared that there might be something wrong with my program or setup. I dont want to break anymore taps. I have checked the runout of the drill and tap. they have less than 0.02mm runout. i am using a floating tapping head. i dont have a refractometer to check the soluble oil level. but when i filled the coolant i mixed 10% oil. I am tapping at 300RPM. I am drilling 30mm deep and tapping 20mm deep. is G32 the right cycle for Fanuc OT? What other things can i change to prevent the taps from breaking?

[HairyWBush]

What size is your tap drill bit?

[Jim Dawson]

I do a lot of 304 SS parts, tapped at 5/16-18 (~8mm), about the same depth as you are doing.

I use these Guhring taps, https://www.westtool.com/default.asp...73079380#tab-1

I get hundreds of parts per tap. Try increasing the drill bit size.

Here are my conditions:
Drilled for 50% thread depth, which is common in SS. Use this if the spec allows it, it does meet our spec.
200 RPM
7 to 10% coolant mix
I use a G84 rigid tapping cycle. Not sure if your Fanuc software supports this.

Critical that the tap is on the centerline. Dial in the tool holder to make sure. I use my Blake Coaxial indicator to dial in.

[Asheen]

im using a 6.9mm drill bit

[HairyWBush]

im using a 6.9mm drill bit

for your 8 mm?
I'm showing a 7.1 mm drill size for an m8

[Asheen]

I do a lot of 304 SS parts, tapped at 5/16-18 (~8mm), about the same depth as you are doing.

I use these Guhring taps, https://www.westtool.com/default.asp...73079380#tab-1

I get hundreds of parts per tap. Try increasing the drill bit size.

Here are my conditions:
Drilled for 50% thread depth, which is common in SS. Use this if the spec allows it, it does meet our spec.
200 RPM
7 to 10% coolant mix
I use a G84 rigid tapping cycle. Not sure if your Fanuc software supports this.

Critical that the tap is on the centerline. Dial in the tool holder to make sure. I use my Blake Coaxial indicator to dial in.

I see the difference between the tap i used and the tap that you use is the color band. i thought that blue band is for stainless steel. What types of material is the gold band suited for? Also your tap is a power tap. i must ask my supplier if he can get the power taps.

My cnc lathe does not support rigid tapping. The chuck takes too long to stop and change direction.

[Asheen]

[QUOTE=HairyWBush;2322707]for your 8 mm?
I'm showing a 7.1 mm drill size for an m8[/QUOTE

the pitch of the m8 tap is 1.25mm. the size that the supplier specifies is 6.8mm

[HairyWBush]

[QUOTE=Asheen;2322712]

for your 8 mm?
I'm showing a 7.1 mm drill size for an m8[/QUOTE

the pitch of the m8 tap is 1.25mm. the size that the supplier specifies is 6.8mm

with either 1 or 1.25 pitch in stainless, my chart shows a bigger drill bit than 6.8mm. I've only tapped a couple metric stainless holes so far, and one was in stainless, so I don't know how great of a difference that will make, but that may be part of the problem.
it also sounds like you're tapping a bottoming hole. if you already aren't, try using a plug tap, THEN a bottoming tap.

[Jim Dawson]

According to the Guhring catalog the blue ring is for SS, but I have had no problem using the yellow ring taps. I was having some problems until I increased the drill bit size.

The Fanuc OT software does suck, it's 30 years old. That's the reason I ripped everything out of my lathe that said Fanuc on it and did a complete retrofit.

[FastFarmer]

The Fanuc OT software does suck, it's 30 years old. That's the reason I ripped everything out of my lathe that said Fanuc on it and did a complete retrofit.

Good move. Given Fanuc and Siemens think USB 3 is a modern "new world" interface... it beggars belief how backwards their controllers are.

[WayneHill]

Have you ever tried cold form taps on a lathe?

Drill as deep as the print allows. Stop the machine before tapping to slap some tap honey on the tap and continue without coolant on the tap cycle. This keeps the coolant out of the hole to prevent any hydraulic pressure on the tap.

https://www.jarviscuttingtools.com/f...p-drill-sizes/