[madokie]

bottoming taps dont remove metal till they hit the bottom of hole ???? BULL,, i have been a machinist since 1979 and in all my experience they DO remove metal gettin to the bottom of a hole.,the cutting flutes on a bottoming tap are NOT reduced in size,from the 2 or 3 flutes at the bottom of tap,and will do some cutting on the way down to the bottom of hole,,bottoming taps are rarley used and will be sharper than a used but good cond tap,and so thats why they cut some getting to bottom of hole..and u say ALL head bolt and main holes are bottom tapped..really ,,just how do u know this ??? u worked in a pontiac engine plant back in the day and examined these taps your self ?? ever section a broken block up and verified this "fact" for your self ?? u get a big flashight and look in a hole an think u see threads at the bottom of hole ?? i dont know either way,but i have never heard about it on this board, and have not seen pics to verify it either,,not that it matters,,i doubt Generous Motors would use bottoming taps,would cost more,would require another secondary machining step on the engine block machining line,and is not really required at least on the head bolts,,they just add more material in the casting and use regular taper taps which dont require a lot of torque to get the tap started which a bottoming tap would if the hole was just drilled and then u try to put the bottoming tap in.. thats why bottoming taps require threads already in a hole, is the torque requirments are too high to start hole threads and continue cutting till bottom of hole is reached,but then u cant tell when that has happened because of the exxessive torque and u wind up breaking the bottoming tap..hence this is why bottoming taps are only used in most materials as a secondary operation to put more threads at the bottom of a hole ,and only when needed, manufactures are not going to do anything not needed..