A way to ensure true tapping every time Bore a clearance hole for any suitable sized piece of round silver steel in the top of your tap wrench shaft. Fit a short length of the chosen silver steel in your drilling machine's chuck, then adjust height so that the tap enters the hole to be tapped. When you begin tapping the wrench will rotate around the silver steel and the new thread will always begin at 90 degrees to the horizontal (tapping true). As the tapped hole deepens you can remove the job from the drilling machine and carry on as usual. I'm not claiming this to be a new idea, but it is a nice, cheap and easy solution to an old problem. Tap wrenches with a bored hole and a suitable shaft should be avialable through ARC Eurotrade in the next few months, although there is no reason why you cannot modify all the wrenches you already have.

Start off every tapped hole truly....