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Build a very strong keychain tool from a Sawzall Blade .

Motivation:
It is often a desperate move scratch at something with your keys.  At best you will tear up whatever you are trying to cut or pry, at worst you will break your key and be stranded.  I've tried to make a keychain tool that could replace a small pocket knife or utility knife  -- so I would think 'where are my keys?' instead of 'where are the scissors?'

Overview:
The first half shows how to make a simple saw keychain.  In the second half I do some more detailed grinding to make a knife-like tool that fits well in my finger tips.

Some key points:
  1. Sawzall blades are very tough metal
  2. Drilled hole with dremel grinder
  3. Shaped and cut with bench grinder

Here is a video of the final tool:


Step 1: Materials

Stuff:
  1. Sawzall Blade
  2. Center punch
  3. Grinder Dremel bit
  4. Drill
  5. Bench grinder

Step 2: Mark Hole and Length

I wanted this to be about the size of a key - so I used my keys to determine the length.

I used an old screwdriver to make scratches to mark the length and hole.

Step 3: Start Hole With Center Punch

Use a center punch to start the hole.  This will keep the bit from drifting around as you try to start the hole.

Step 4: Make a Hole

It took a long time to make a hole in the blade.

I tried a regular drill bit with poor results.

A blue grinder from a dremel kit worked well, the bit was nearly destroyed.

I made a jig by putting nails into a board very close the blade.

Step 5: Is the Hole Big Enough?

Test the hole. 

The hole here is a little too small to fit over both rings of the keychain.  Measuring the keychain, the hole needs to be almost 0.2"

Step 6: Grind to a Shape

I used a bench grinder to shape the saw.

Removing several teeth makes the saw easier to hold.

Step 7: Polish on Grinder

To clean up the sides of the blade, use a fine grit wheel and a light touch.

Step 8: Cut to Length

Cut the blade to length on the square corner of the coarse wheel.

Step 9: Put on Key Chain

Step 10: Test It Out

The sawzall blade cuts on the pull, so the key chain and keys can be used as the handle.

Step 11: Make Another With the Other End of the Blade

The fat end of the blade can be made into a second tool.  This part already has a good size hole.

Step 12: Grind Shape and Polish

Shape on the coarse wheel and polish on fine.

I tried to give the back of the blade a curve.  Also ground off several teeth to make a little handle.

Step 13: Now We Have 2

Here are the final pieces.

Step 14: Put Them Both on a Key Chain

Step 15: Test It Out

This one is pretty beefy.

Step 16: Make Better

I've changed the shape to make this a more practical hand tool.  As a saw it just ripps stuff, this is more like a small knife or x-acto blade.

It is now pretty kick-ass.

I will(might) post details when(if) I get a chance. 

Step 17: Testing Some More

Here are some more images of the saw in action.  It is tough enought to screw in a screw, cut a tire, mangle rusty car metal.

Step 18: Problems

The saw is good, but it does more ripping than cutting.  There is also a spot that digs into my finger.

Step 19: Shaping Tools

Here are some dremel tools that are able to grind the tough metal.

Step 20: Start of the Grinding Wheel

A bunch of the teeth have to go, in order to form a blade.  The rough cutting is done on the grinding wheel.

Step 21: Detailed Work With Dremel Tools

The inner curve was hard to get right.  I put the dremel grinder in a drill press and held the knife in my fingers.

Step 22: Sharpen

The blade is only angled on one side (like a chisel).  The back is flat.  This allows you to sharpen the knife be pressing the flat side against a flat sharpening stone.

Step 23: Sharpen the Curved Side

I have some fine stones with curved edges.  I have these for sharpening curved wood lathe chisels (gouges).  They need honing oil and can produce a very sharp edge -- probably sharper than is really needed.

I sharpened these by going back and forth between the curved side and the flat side.  You sort of get a little sharp edge that bends back and forth, when it is gone the blade should be very sharp.  I test the sharpness by dragging the blade gently across my fingernail  -- it should immediately catch the nail.  In some of the pictures you can see little chunks of my finger nails missing from this.  A dull blade will just slide across the surface.

Step 24: Polish

I got a decent polish by rubbing the knife on a piece of wood covered in a fine rubbing compound (for a car).  At this point the tool is tiny and sharp, so it was pretty hard to handle.

There are dremel tools that are grit and rubber  -- but I didn't have any on hand.

Step 25: So That's How Its Done!

Be sure to keep your keys and touch screen phone in different pockets!
I hope you don't trip with this in your pocket!
<p>Cloudy with a chance of &quot;Who puts a razor sharp blade within 3&quot; of their _____&quot;</p>
<p>Ha! Somebody with 4 little kids.</p>
<p>Be sure to keep that out of your pocket and well away from your nuts.</p>
great idea! i read an entry last week where a chainsaw blade was cut to length and, garden hose handles glued to it to make a &quot;pocket chainsaw&quot; bravo (hose clamps would work well too). i saw your gutter cleaning post, i recently used a leaf blower to clean gutters, got the bulk of the leaves out by hand temporarily unclipping the gutter as i went then took to it with the blower, worked great even in the wet.
Thanks -- I had just read the 'pocket chainsaw' when I did this

About This Instructable

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Bio: Married to Domestic_Engineer (but I call her Meghan).
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