(quoted from post at 06:44:13 06/03/15) The answer is in your original post, the broach is designed for cast iron, not stainless steel, stainless doesn't present any particular problems when using the proper tooling and lubricants, it will pull harder than cast iron, and you need to monitor tonnage closely and make sure the broach is completely free of chips between pulls, and the one rule you must never break is about maximum length of cut for the particular broach being used, the length of cut you can get away with in cast iron will be significantly more than a broach with the same pitch in stainless. My guess would be that the problems you have came from exceeding the maximum length of cut, compounded by an improper grind on the teeth for the material being cut, and possibly use of the wrong coolant, oil should never be used on cast iron, and for maximum tool life, should always be used on stainless and most other tough alloys. Most of our broaching work is on tough, pre-hardened alloys, exotics, and stainless, we turn away cast iron work because we just are not set up for it. What is the spline you are trying to cut and where are you located? We may be able to help. Good luck, I've been where you are, and it's no fun.