Hi all,

I used to tap steel 9310 using 8-32NC tap, depth of blind hole 0.3inch, thread .23inch. Since we have changed water based coolant to oil based coolant (prisma 517 Total) I cannot make even one part. Original speed 1832RPM (feed 57.25inch/rev). Today I have tried 1000RPM - tap is dull, 200RPM - tap is destroyed, original speed tap is dull. Of course I adjusted feed to certain speed, even with two pecks - nothing. I have compression holder and still cannot tap those damn holes - what am I doing wrong?? Thank You for any answer..