I have used tapping units like the photo in Bobs post they work great. But are a bit pricy IIRC over $1500 US to get set up new. And like I mentioned on the other post IMHO Tapmatic is also an excelent product.
On another thought an often overlooked "tapping Head" that many of us have about the shop is the cordless drill driver. They have adjustable torque settings and reverse. If you have trouble holding the tap square to the surface you can use a tapping block. When I worked at the yacht builder the Tech rep from the window vendor taught me this. I have used my dewalt sucessfully tapping aluminum. Have not broken a tap with it. Use common sence and the right tap for the job and you should have no problem.
Ad maiorem dei gloriam - Ad vitam paramus