 A 'tap' isn't a tap | |
Normally I would agree that a tap won't work. The channels are too wide to keep the blank engaged and turning properly. The mysterious 'tap' is cut from scratch, or a bolt that has been modified with cutting channels small enough to handle the blank. If a blank is too thin, either stack them or sandwich it between two layers of metal/plastic. This will give the blank some rigid support and allow the cutting tool to stay engaged. The jig clamps to the tool post. The post is gradually fed into the cutter to allow at least a full turn of the blank until the correct depth is reached.
The stacking and/or sandwiching helps keep the rough edges down. GRANTED this isn't precision gear cutting for the space shuttle fuel feed system, its a hobby cut i.e.- (at least in this case) hobbing. |