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This rather dated article recommends using a shortened reciprocating saw blade to punch through drywall. I have an old blade (intended to be used to cut wood, as far as I can tell) that I'm happy to cut short for this purpose, but the page's recommendation of cutting through the blade with cable pliers is a non-starter. Perhaps recip saw blades were thinner in the 80s.

I have a decent selection of tools in the house, but not anything particularly geared toward metalworking. How can I cut through this blade to shorten it? I do have a recip saw blade that appears to be intended for cutting through metal (it has an icon of what appears to be a girder on it, and is red) but I'm not sure if another blade was the target that they had in mind for it.

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    I would just use a short demolition or medium tooth blade and flatten the tool angle to control depth. That's actually more accurate as it reduces the plunge depth of the reciprocating tool's action with respect to the wall.
    – isherwood
    Apr 13 '20 at 0:52
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    A drywall cutout tool is better. Even an oscillating tool is better than a recip for this. If you don't get the length just right, and even if you do, the job will be a dog and you'll get kickout every time you cross a stud. I really wouldn't recommend this approach - it sounds clever, but is likely to just make a mess and give you a headache.
    – J...
    Apr 13 '20 at 13:03
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    @isherwood That's how I do it. It can be a little tough to get a clean start sometimes, but I don't do it often enough to have become proficient at it. I've seen people who can do it cleanly every time. Apr 13 '20 at 14:03
  • It also depends how your tool holds the blade. Those that clamp a screw onto the side of a blade will be fine, but those that use a through-hole won't have that so it could drop the blade during use.
    – Criggie
    Apr 13 '20 at 20:48
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    Please wear eye protection -- especially if you are using parts outside of their design, or broken or cut parts. The chance of the blade bending and snapping is higher. Best regards.
    – Philip
    Apr 14 '20 at 4:01
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I just save my broken blades for this.

Clamp it in a vise, where you want it to break off and hit it with a hammer very sharply. It should snap off (make sure the part you want to KEEP is in the vise).

If you have to work it back and forth a little, you can clean up the edges on a grinder.

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  • I would put the disposed part in the vise, so the vise does not damage the teeth of the part Im keeping. Apr 13 '20 at 2:38
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    @MadsSkjern You can leave the teeth off the end of the vice and still put the 'keep' part in the jaws. Doing it the other way risks bending the kept part.
    – J...
    Apr 13 '20 at 12:59
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    @MadsSkjern - you put it horizontal into the vice, so the teeth just protrude at the top. waste bit comes out the side. Wear goggles at least.
    – Tim
    Apr 13 '20 at 16:08
  • This worked super well! I wouldn't recommend using it for my intended purpose, though—it was much easier and cleaner to just cut the drywall with an exacto knife. Maybe the drywall in the 80s was more sturdy.
    – intuited
    Apr 14 '20 at 20:57
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Use pliers or vise grips to grab the blade on each side of the line you marked for the cut and just wiggle back and forth. Metal fatigue will cause the blade to break. This works better on stiff brittle metal better than soft flexible metal.

This is a hack thou, and if you are doing this often enough, there is a much better way which is a dedicated drywall cutout tool

enter image description here enter image description here

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    +1 SOOO much better and easier to use by the way. If you are not doing a lot of drywall and don't want to pay for that tool and have a Dremmel tool for other reasons, you can also get a drywall bit and attachment to make your Dremmel tool into one of these.
    – JRaef
    Apr 13 '20 at 21:49
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The composition of the metal in a recip blade may be a composite, hardened steel for the teeth, softer stuff for the backbone, or it could be lower grade throughout. The hardened stuff is pretty brittle, and the "softer" metal of the backbone gives it strength.

If you have a dremel tool (rotary hobbyist type) or a side grinder, you can score the blade at the desired location. Even a bench grinder can be used, if one exercises greate care. It's certainly possible to cut through the blade, but once the score is of sufficient depth, you may be able to snap it. For testing, make your first cut farther out than the final location.

It may be possible, depending on the material of your blade, to use a metal file to score the blade, but that will require a bit more elbow grease.

If using a power tool, consider to dip the cut in water periodically to keep it cool and to maintain the temper of the steel.

Lacking the above tools, it's also possible to clamp one end and work the other end with pliers until the steel fatigues and breaks of its own accord.

As I typed this, two additional answers have appeared, but this is different enough to retain.

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If you also own a jigsaw you may find that its blades will fit well enough in the recip saw that you can use them instead. Maybe they are already short enough for the purpose.

I'm thinking of this type of jigsaw blade:

enter image description here

which has a similar shank as a recip blade:

enter image description here

(There are also quick-release style jigsaw blades without a hole - these will almost certainly not work).

A caution is that the fit could be "sloppy" so I'd test it out carefully before committing to an actual cut.

FWIW you can also fit a hacksaw blade in a recip saw, though the extra length would certainly not be any help in this specific case.

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As an alternative, you may be able to temporarily fasten a spacer to the wall, to hold the body of the tool further away and reduce blade penetration that way. If you're lucky you may be able to fix it to the part you're going to remove. 2x2 would be one example of a suitable material

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Caveat- this is potentially dangerous...

I have 'cut' blades using a sharp cold masonry chisel and lump hammer. BUT, you need to put a piece of heavy cloth, piece of old towel etc. on top of the blade or parts of it will dangerously ricochet away, potentially hurting yourself.

You'll also need to do this on a solid metal surface, the flat part of a heavy vise is ideal.

Lay the cloth on the vise, then lay the blade and fold the cloth over it. Position the sharp cold chisel where you want the blade cut and then one sharp hit with a heavy hammer should snap the blade.

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