Instructables

Plunge Cut with Sawzall

Here's how to saw slots in the middle of something without drilling holes first.
It's called a "plunge cut". This particular method works with a sawzall, sabersaw, handheld jigsaw, or whatever you want to call it.

You've all learned the drill-holes-for-sawblade technique already in industrial Arts class.
For this plungecut method, you don't drill any holes.
You just start the saw, rest it on its guard, rock it forward, and BELIEVE!

If your faith is pure and you do it just fast enough the blade doesn't stub its toe and get bent.
In these pix Fungusamungus and myself are cutting slots for a skeg box on a CLC boats "Pax 20" kayak.
 
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Step 1: Rest, Rock, Believe, Cut.

Here it is again.
Rest the blade guard thing on the work. Usually the guard is just big enough that you can do this without the blade touching the work.
Run the saw and rock the oscillating blade down into the work.
If you're not confiden't you'll spend some time watching it waggle around gouging scratches in a fan-shaped pattern.
If your faith is pure it'll just gouge one scratch that gets deeper as you rock it down until it goes through the material.
Then raise the saw vertically and continue the cut in the normal manner.
Once you have the trick working you can do cuts through beams, doors, and other thick material.

Step 2: Widen the Slot

Here Fungusamungus is widening the slot by sawing another slot parallel to the first one, then veering from one cut to the other to make the chunks fall out, then shaving the sides of the slot with the saw. If you don't want plunge cut practice you can just start veering around from the first cut.
ilpug2 years ago
I saw a blade in a store that was rounded upwards in an odd way, supposedly meant for plunge cuts. I wonder if one could easily be made from a normal sawzall blade.
If you want the blade not to stub it's toe just put a very small amount of weight behind it and alot on top of it, I used to spend six hours minimum a week with one of these, I will post what I call reciprocating snooker sometime, fast paced, high power billiard action...
0.775volts7 years ago
I've done this before with both jigsaws and sawzalls (tiger saw if you have a porter cable and for some reason cannot recognize the shape in the picture). one thing i'd recommend is to practice with an old blade and scrap wood, it takes just a little pracitce to get it down pat. also, should you bend a blade doing this or numerous other things, if you have a vice or big heavy peices of metal handy, those will help you to bash the bent blades back straight.
the blades that bosch sells for recip and jigsaws have a single end tooth with a larger gullet just for this sort of thing (and they're a lot tougher than the dewalt blades). still, to resist the bending, i took a few of the the bent blades and cut them short and ground them to a more suitable shape (they work better in shallow blind plunge cuts when they're short and stiff) oh, and btw... the saw is a DW303
Maybe its just me, but I wouldn't recommend bending a sawzall blade back to straight. Bending it, to the best of my knowledge, weakens the metal and bending it back even more so. You'll end up with a straight blade, but its tensile (*sp?) strength will have been reduced at the bend and it very well might break when you go to use it.
as i remember it, bending metal adds discontinuities into the structure and can even make it stronger. i imagine it would be difficult to get it perfectly straight again, though (eve tray bending a coat hanger back into it's original position after straightening it?)
whenever i've bent a blade, it has always been a very gentle bend, with a large bend radius and no crease, if it were to get truly buggered i'd ditch the thing. sometimes, a bent blade is your last option.
lemonie7 years ago
I can see this on CSI... They examine the wound with varios probes, lights, sprays, computers etc. They notice one of the suspects has been building a skeg box...
mrmath7 years ago
Look at all those orbs in your workshop. The place must be haunted! IT'S DUST PEOPLE! Sorry. Too much Ghost Hunters.
I think my $17 HF one would turn my hard work to sawdust if i tried that. Nice job on the boat.
theRIAA7 years ago
i have a sawzall that has a rotary feature for this kind of thing, it "digs"
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