Wayne,
I do not think that the roughness of the finish was necessarily a desired thing, but merely a byproduct of the blades in the broaching machine wearing and getting chipped. I am not sure how you could achieve an uniform agressive finish in a linear machine like a broach. It is easy to do in the case of a circualr mill, by adjusting the feed rate to leave ridges, but I do not believe that you could do so with a linear cutter.
I would hazzard a guess that the blades were only changed when the machine could no longer produce a deck that was within tolerances. It would only make sense that all blades were all changed at the same time and properly set to their proper incremental cut. A fresh set of blades, set correctly, should leave almost no marks behind until the edges of the blades began to nick and wear as time on the machine progressed. We use proggessive broaches in our shop to cut internal keyways, and they leave almost polished surfaces when done, as long as they are not worn out. It is really only the last blade that passes over the material which leaves the mark for the most part, since each progressive set of blades cuts slightly more metal. As long as the last blade in the cutter is neat and clean, the cut will probably be so as well.
My opinion is that not all pads had anywhere near the same ammount and depth of broach marks, and to judge that as if they did is silly. Hopefully, most judges, realize this and judge the pad finish accordingly. In the case of my car, I had several mechanical judges look judge my pad, and several made comments about the total lack of broach marks, but none ever failed the pad finish. I think that most just recognized the pad for what it really was, an untouched, original pad, and judged it accordingly.
Regards, John Mcgraw
I do not think that the roughness of the finish was necessarily a desired thing, but merely a byproduct of the blades in the broaching machine wearing and getting chipped. I am not sure how you could achieve an uniform agressive finish in a linear machine like a broach. It is easy to do in the case of a circualr mill, by adjusting the feed rate to leave ridges, but I do not believe that you could do so with a linear cutter.
I would hazzard a guess that the blades were only changed when the machine could no longer produce a deck that was within tolerances. It would only make sense that all blades were all changed at the same time and properly set to their proper incremental cut. A fresh set of blades, set correctly, should leave almost no marks behind until the edges of the blades began to nick and wear as time on the machine progressed. We use proggessive broaches in our shop to cut internal keyways, and they leave almost polished surfaces when done, as long as they are not worn out. It is really only the last blade that passes over the material which leaves the mark for the most part, since each progressive set of blades cuts slightly more metal. As long as the last blade in the cutter is neat and clean, the cut will probably be so as well.
My opinion is that not all pads had anywhere near the same ammount and depth of broach marks, and to judge that as if they did is silly. Hopefully, most judges, realize this and judge the pad finish accordingly. In the case of my car, I had several mechanical judges look judge my pad, and several made comments about the total lack of broach marks, but none ever failed the pad finish. I think that most just recognized the pad for what it really was, an untouched, original pad, and judged it accordingly.
Regards, John Mcgraw
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