trouble tapping s/s

You might want to look into a forming tap rather than a cutting tap.

s/s is a true bastard to work in, tending to tear more than cut, and 'gummy' for a better way to phrase it.

I remember the Walther PPK/S when it was made in s/s and regular steel. The s/s models were horrid as to finish and damn near crunched when the action cycled.

Allen

I doubt you will find using a forming tap as opposed to a cutting tap to be easier in stainless settl. Typically a form tap is used for ductile material - primarily aluminum and copper based alloys.

Stainless work hardens so as soon as you start to deform the material and form the threads you will experience work hardening. You might get away with a small thread size (small diameter) or a fine pitch but I think the larger you go or the coarser the pitch would get progressively more difficult.

I am assuming you are using a standard tap that has a tapered start and the last half of the tap or so cuts a full thread form. Assuming you are using a standard tap I assume you are NOT using a bottom tap. The bottom tap has a very small lead and starts to cut full thread forms in the space of 1 1/2 turns or so. You only use a bottom tap when you have a blind hole and use it only after you have tapped as much as possible with a standard tapered tap (tapered lead, not tapered thread as in an NPT pipe tap).

With regard to a multi stage tap. The general idea here would be that you would in effect be taking smaller bites as you go thus needing less torque to turn the tap. That shouldn't be necessary because nothing you've spelled out is that exotic or out of the ordinary.

Are you using a tapping fluid? The best I've seen is Tapmatic hands down.

Travis

A simplified reply to your inquiry is that the 300 series stainless steels tend to work harden. This means increased tapping effort, even if there are no blue chips. If the quantities of holes are small, I suggest tapping by hand, and switching to a new tap when you experience increasing tapping effort. If tapping by machine, use a torque limiting clutch.

Deep Cryogenic treating can significantly increase the strength and useful life of your taps if the material they are made of has .4% carbon or above.

Taps get dull fast in SS. They last longer with plenty of cutting oil. The best taps I've found are simple two fluke spiral point taps from a quality supplier.

How many holes and are you doing them by hand or what?