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Although it’s primarily popular among electricians, Greenlee’s Slug-Buster punch works beautifully for cutting a perfect hole in sheet metal while exerting minimal effort — something almost anyone will end up needing to do at one time or another.  And at around $30 for a basic set, there’s really no excuse not to own one.

The basic Slug-Buster set includes a draw stud, die, and a matching punch — with which you can produce a clean hole in five easy steps:

  1. Drill a pilot hole
  2. Push the draw stud through the pilot hole
  3. Thread the punch onto the opposite end of the draw stud
  4. Tighten the draw stud

As you tighten the draw stud, it pulls the punch through the material, splitting the waste material completely in half and making it easy for you to remove the waste from the die.  That’s also where the Slug-Buster earns its name.  (For those who want to keep the slug intact, Greenlee offers “standard” knockout punches which operate in the same manner but without splitting the slug.)

To see the Slug-Buster in action, take a look at this Greenlee demonstration video. Although the video focuses on their new self-centering punches, the operation is identical.


The smallest (1/2″) set of Slug-Busters (1/2″) start at around $30.  And if you cut or drill holes into sheet metal, you can explore Greenlee’s wide variety of multiple-size kits and tool options.  They also offer readily-available replacement parts, so if you dull out a punch you won’t need to reorder the whole set.

Slug-Buster Knockout Kits [Greenlee]
Street Price [Google Products]
Big 1/2″ to 1-1/4″ Kit Via Amazon [What’s this?]


8 Responses to Greenlee’s Slug-Buster Knockout Punch

  1. Nick Carter says:

    They also make shapes for various electronic components, squares (Ebay is your friend), etc. Very handy tools for many purposes.

    I lucked into buying the hydraulic puller tool (like a tiny portapower) they sell for these ($7.50! They had no idea what it was at the garage sale) and it speeds up the process of pulling the halves together, consider getting one if you do constant work with them, much easier than cranking a wrench around.

  2. john says:

    My dad worked at Kodak for years fabricating electric and pneumatic panels… After he retired I “inherited” a complete set of these. They are the best tools for making perfectly round holes… and don’t distort the surrounding material. The one drawback it that they are not cable of making blind holes as you need to be able to get to the backside to put the cutting edge on. All in all, a great tool that beats a hole saw in many aspects.

  3. Fred says:

    While they do require a pilot hole to be drilled, they produce the exact sized hole for conduit/emt.

  4. MT says:

    Is the idea that this is more accurate than a center punch, drill, & block of scrap wood? Or for pre-installed pieces?

  5. MT,

    This is intended for large diameter holes, especially in environments where a drillpress cannot be used. When dealing with metal, your only powertool options are to use a holesaw, jigsaw, Dremel, or similar cutout tool. Using a holesaw with a cordless drill is somewhat inaccurate, requires some finishing work, and is incredibly frustrating at times.

    For a 1/2″ hole, it might be a better idea to use a holesaw instead of a Slug-Buster. But when you need a larger hole, say 1″ or greater, a knockout punch is going to be much easier and quicker to use. Don’t forget that a large holesaw cut requires the use of cutting fluid and careful cleanup of metal dust and fragments.

  6. I ran across a fairly affordable set the other day: http://www.oselectronics.com/ose_p64.htm

    Being made by Philmore and stocked by an electronics supplier, I assume it’s designed for mounting vacuum tube sockets in aluminum radio chassis. Maybe it’ll work on steel electrical boxes, too?

  7. Coach James says:

    Checking Amazon now, I don’t see any prices even close to $30. Anyone know where a basic cheap set can still be found?

  8. Paul says:

    Pro tip:

    If you have a cordless impact driver, put a 1″ socket on it and it will punch a hole in a stud or panel in about 7 seconds.

    If you have a powerful drill (more powerful than an XRP Dewalt cordless drill) than it can work also, but impact drivers work much better.

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