I have used mostly 2 fluted taps over the years. The problem with 4-fluted taps is that the flute have to be smaller, and therefore move a smaller volume of chips, before they begin to add pressure to the turning of the tap.
If you use your fingertips on a tap handle, you can FEEL the resistance when a tap is starting to bind. STOP! Back that tap out to break out the chips. Back the tap all the way back out and brush the flutes clear, and the teeth clean. Then oil both the tap threads, and the existing hole in which you are running the tap before trying again.
I found, in shop class, that too many guys were INSISTING on taking a full 1/2 turn with the tap each time, whether they felt resistance or not. Invariably these were the guys breaking taps. They would watch me, and question me why I stopped turning the tap at 1/4 or 1/3 or some other turn less than 180 degrees, and seemed surprised that I stopped because I began feeling resistance. :shocked2:
Like Zonie, I am not in production mode, so I take my time to do it right, and protect the tools I am using. If you think taking a few extra minutes to tap a hole in a lock plate is frustrating, think how much MORE time it takes to get that broken tap OUT, and then find a replacement! :shocked2: :idunno: :idunno: :nono: :surrender: :hmm:
I am also painfully aware of how long it takes to put a good edge back on sharp tools, like knives and chisels. While I have never been set up to resharpen taps, ( and don't want to be), I can't imagine the PITA it must take to sharpen or make these taps, if you had to do it by hand.(18th Century Gunmakers made their own taps using files, and then a "Drill Plate", which they often considered to be the most needed tool, right behind their anvil, hammers and swage block.)
Along these lines, I once made 144 Square-shaped nuts for a friend's 6 lb. cannon, cutting the square stock on a bandsaw, then center punching them, drilling them, and then tapping all 144 "nuts". It took a whole evening , and Ray was thrilled that I got them all done so quickly, and managed to NOT break a tap, doing it. In fact, he watched me tap several of the nuts to see how I managed Not to break a tap, as he had broken a tap for about every hole he had threaded on his own.
Once you have that experience, running by a hardware store, and buying nuts for a few cents a piece seems VERY CHEAP!
I bought a couple of taps that have 4 flutes, but these are in large diameters,(1/2" & 5/8") so that the flutes remain large enough to move the chips freely. I bought them to use for tapping wood base plugs for screw in stoppers, and, possibly, to thread the inside of the mouth of horn tips to fit on a threaded powder horn mouth. I have never gotten to this last item, but its on my list to try to do. I have the matching dies for doing the male threads. These, of course, are much softer materials than steel. :hmm:
