Rolling of Internal Threads

Rolling of Internal Threads

Rolling of Internal Threads - Unfortunately, the rolling process is not practicable for making most internal threads; the required forces are too high, and there is insufficient space within the area involved to permit the required rolls to be arranged and supported. However, internal threads, up to about 1/2 inch in diameter can be formed in holes in ductile metals by means of a flute less tap.

Such a tap and its special cross section are shown in. The forming action illustrated in, is essentially the same as in the rolling of external threads. Such taps, which come in both plug and bottoming types, are especially suitable for forming threads in dead end holes because no chips are produced. Rolling taps also produce somewhat better accuracy than cutting taps.

Left Fluteless Tap For Forming Internal Threads

However, the required torque is about twice that for cutting taps, and the hole diameter must be carefully controlled in order to obtain full thread depth without excessive torque. Very high friction is involved, and a lubricating fluid should be used; water soluble oils seem to be most effective.