There already are several instructables on making MineCraft Swords. Posting mine as well because I didn't find an instructable describing the method I used.
All you need is a slat of wood, screws and paint (white, black, brown). Depending on the paint you use and your preferences you could use varnish as well.
Tools: saw, drill, screwdriver, sanding paper, paintbrush, painters tape, sharp knife (razor blade) and scissors.
The saw is more like decoration than a toy to play with. I.e. when kids would actually use the sword and try hacking a real tree, it won't probably last long.
Step 1: Getting the Right Slat/lath
You'll need a square slat (Or lath.. I don't really know the difference between a slat and a lath). So width and height have to be equal.
The width/height are going to determine the total length of the sword.
assume width (=height) = 1.5 cm, then the length is going to be 23 * 1.5 cm = 35 cm (approximately)
So the other way around: suppose you would want the sword to be 1 meter in length, the width (and height) should
be 100 cm / 23 = 4.3 cm
(calculations should work with inches as well :)
The sword I made is about 39 cm long. (width/height of slat: 1.7 cm)
The length of the slat should be at least 84 * width. So for above example where width = 1.5 cm, the slat should be 84 * 1.5 cm = 126 cm. .... to be sure you are going to want it to be 150cm.. just in case something goes wrong and you need some extra wood:)
anyway... make sure it's square and you have enough of it :)
Step 2: Cutting the Slat
Cut the slat in pieces. Make sure you do this very precisely or otherwise you will have to do a lot of sandpapering later on. Cut the pieces perpendicular and make sure the length is correct.
The length of the pieces is going to depend on the width/height of the slat. To follow the previous example of 1.5 cm, you are going to need:
1 piece of 7 * 1.5 cm = 10.5 cm (from now on we'll refer to this piece as the 7 piece)
2 pieces of 6 * 1.5 cm = 9 cm (the 6 piece)
6 pieces of 5 * 1.5 cm = 7.5 cm (the 5 piece)
4 pieces of 4 * 1.5 cm = 6 cm (the 4 piece)
5 pieces of 3 * 1.5 cm = 4.5 cm (the 3 piece)
2 pieces of 2 * 1.5 cm = 3 cm (the 2 piece)
I suppose it's clear that when your width/height is different, for instance 1.9cm , you have to substitute 1.5 for 1.9 in above list. .. so you you are going to need 1 piece of 7 * 1.9cm = 13.3 cm etc.
After cutting the pieces, sand them. Especially the top and bottom should be sanded. It's really simple at this stage, but quite annoying when you have to once the sword is assembled.
Step 3: Laying Out the Sword
Use the pieces to lay out the sword.
From top-left to bottom-right:
5 piece (6 times) gap 2 piece
5 piece gap 3 piece
4 piece gap 3 piece
2 piece gap 4 piece
3 piece (2 times)
..or just look at the picture.. it's pretty self explanatory
Step 4: Drilling and Screwing
Right, now we start assembling the sword...
The screws you are going to need should be roughly 1.5 * width.. so when the width = 1.5 cm, they should be 1.5*1.5cm= 2.25cm.
Screw the pieces together as shown in the pictures. You are going to want to drill a hole first, or the pieces will split when you put in the screw. Make sure you use a drill bit with the right diameter.
Before drilling give it some thought as to where you want to drill... The first picture shows the first two pieces with two screws. The second picture shows the third piece attached to it... you don't want the screws of the 3rd piece hitting the screws of the second piece...
I used two screws for each piece... except for the 2-pieces.. i only used 1 screw as i was afraid the wood would split. (even after drilling a hole) ... used some glue as well there
Step 5: Sanding
Sand the sword... the better job you do now, the better the end result will look.
Step 6: Painting
I suppose this step is pretty self explanatory as well...
- I used cheap acrylic paint. It dries incredibly quick so I could finish the whole sword in one go
- use good painters tape. not the rough paper, but the smooth paper.. it will work much better in this case
-you are going to mix paint to get the right colour... do all the squares that have to be the same colour in one go (back and front) .. you are not going to manage to create the same colour again. (It will always be slightly lighter or darker)
-to speed the drying process, you could use a blow dryer... (depending on the paint)
-use a razor blade and metal ruler to get nice straight lines
-carefully pull painters tape off.. don't damage paint under it. (use razor blade or needle to get it off)
-use a good (round) paintbrush and take your time.
I started with the black, then the brown, dark grey, white and finally light grey
Step 7: Finishing It Off
I finished it off by spraying a thin layer of transparent varnish on the sword.
You can skip this if you are happy with the result of the previous step
..you can now go back to your electronic device and play MineCraft