Greenlee radio chassis knockout punches, lot of 13, $14.

Chassis 'knockout' punches are designed to do a job that's more difficult than it sounds at first - create a clean, accurately-located hole in sheet metal, plastic or fiberglass. The guy I got these punches from had retired from a job as a technician with the telephone company, and he told me that he could not have done his job without them. Greenlee makes the most popular and sought-after chassis punches you're going to find, so you're advised to take a few minutes to learn about them!

Greenlee chassis punches are so popular with electricians, as well as guys in the air conditioning business, because they regularly deal with situations where they have to punch holes through metal boxes containing electronics or junctions so that the wiring can be run into and out of the boxes.

To use one of these tools, you first drill a small pilot hole exactly in the center of where you want the large hole to be. You then place the bolt through the hole, and by tightening the bolt, the punch cuts a clean hole right where it is placed. Of course, most do-it-yourself home mechanics will likely never have any use whatsoever for these tools, but for the guys who do use them, they're indispensable for accomplishing the task they're intended for.

These chassis punches are specialty tools that cost between $40 and $80 apiece, so this buy was a really good deal at a bit over a dollar each.

These Greenlee chassis knockout punches sold on eBay for $78.

Photo of Greenlee radio chassis knockout punch lot of 13