Long story short, I can't get a single tapped hole without the tap breaking in 303. It doesn't even make it .125 deep before snapping. This is my first experience with stainless, so I'm sure there's a myriad of things I'm screwing up that I'm not aware of, despite my best efforts at utilizing Google.
Just to verify I wasn't getting slippage or encoder problems, I tapped a bunch of 1/4-20 in aluminum with no issues, so the machine seems fine (Haas 2005 Mini Mill w/ rigid tapping). I was also able to use a straight flute plug tap from a cheap tapping set from amazon to tap about .2 deep (simply a 'screw it, let's try this moment'). It snaps if I go the full required depth to get full threads, unsurprisingly. It got further than the form taps have though.
Anyways, details....
Material: 303
Tap: Form Balax 4-40 2B TiN
Tap Drill: #39
I'm using 20 SFM. Flood coolant (Kool Mist)
When drilling, I'm taking a .002 chip load at 50 SFM and .045 pecks.
I'm using an ER16 collet for holding. I don't appear to be getting slippage when marking with a sharpie.
I raised the feed height to ensure the spindle is up to speed and synced with the Z axis.... just trying to cover my bases.
I'm considering going to a #38, or even a #37 (#39 is recommended by Balax), but figured I'd see if anyone had some input here before continuing my campaign of death to 4-40 taps and my bank account.
Just to verify I wasn't getting slippage or encoder problems, I tapped a bunch of 1/4-20 in aluminum with no issues, so the machine seems fine (Haas 2005 Mini Mill w/ rigid tapping). I was also able to use a straight flute plug tap from a cheap tapping set from amazon to tap about .2 deep (simply a 'screw it, let's try this moment'). It snaps if I go the full required depth to get full threads, unsurprisingly. It got further than the form taps have though.
Anyways, details....
Material: 303
Tap: Form Balax 4-40 2B TiN
Tap Drill: #39
I'm using 20 SFM. Flood coolant (Kool Mist)
When drilling, I'm taking a .002 chip load at 50 SFM and .045 pecks.
I'm using an ER16 collet for holding. I don't appear to be getting slippage when marking with a sharpie.
I raised the feed height to ensure the spindle is up to speed and synced with the Z axis.... just trying to cover my bases.
I'm considering going to a #38, or even a #37 (#39 is recommended by Balax), but figured I'd see if anyone had some input here before continuing my campaign of death to 4-40 taps and my bank account.