Introduction: Kama Made From an Old Saw Blade With Basic Tools
Hi Instructables Community,
this week I present you my entry for the 2016 Zombie Weapon Challenge which was initiated by Mike Fulton from the MF Woodshop. He started this challenge to celebrate the start of the new "The Walking Dead" and 24 other makers followed his call and produced a range of improvised Zombie Weapons which you can check out here.
So looking for a new approach to the subject I decided to use a traditional Japanese farming tool called a Kama. The Kama is similar to a sickle and used to harvest crops. Its shape lend itself to be used as an improvised weapon and found its way into various martial arts such as silat, karate and ninjutsu.
So follow me to see how I turned an old saw blade into a "Zombie slaying" Kama.
Step 1: Materials
Since the blade I had in mind was rather larger and since I do not have a forge to shape metal in my current setup the only choice was to create the blade with a technique called stock/material removal.
As a base material I used an old saw blade that was entirely made from HSS (High Speed Steel) with a hardened & tempered periphery.
For the grip I decided to re purpose some old oak I had in my shop so the only "new" material used was some 6mm brass tubing for the pins and paracord for the handle wrap.
Step 2: Preparing the Template
Tracing the outline (or at least part of it) of the saw blade onto some paper enabled me to design a shape that would use the curve and features of the saw blade.
Once I was happy with my design I transferred it to thin cardboard to add stiffness and make it easier to work with around the shop.
The cardboard template was trimmed to size using scissors & scalpels as well as a rotary cutter.
Of course you can use whatever cutting tool you feel comfortable to use for this task.
Step 3: Transferring the Shape
For the following steps I decided to transfer the shape directly to the saw blade. This was as easy as it sounds using the template and a permanent marker.
Step 4: Prepare Cut Lines
Since the final design is relatively complex it would have been rather difficult to attempt to cut it out from the saw blade like that.
With a straight edge I drew a simplified shape using only straight lines approx. 0.5cm outside of the original shape.
As I've mentioned before the saw blade was already heat treated so I didn't wanted to make those cuts too close to what would later be the cutting edge.
Step 5: Rough Cut
Using a sacrificial straight edge I was able to cut out the rough shape with my angle grinder. I used a very thin 1mm blade which went through the material very fast and precisely.
Make sure you wear personal protection equipment such as a faceshield and goggles since those thin abrasive blades can easily shatter and ruin your day.
Step 6: Preparing the Shape
As I said before those thin abrasive wheels can shatter easily when put under the wrong stress which could occur when cutting long segments or even worse segments with a radius.
To avoid this I made several relief cuts moving up to 1-2mm to the outline of the final shape. This enabled me to make several short straight cuts removing a lot of material which got me much closer to the desired shape.
Now if you own a belt grinder you could do this with a course grit belt but even then it would be worth the time to work with the abrasive wheel since those wheels are much cheaper than for example a 2x72" grinding belt.
Step 7: Rough Shaping
For this step I used a 40 grit flap sanding disk on my angle grinder. This removed material quite quickly so I had to be careful to keep the grinder moving as to not overheat the material.
Step 8: Refining the Shape
It was a little tricky to remove material in the corner where the edge would later meet the tang. The space was too small to effectively use the angle grinder without running the risk to remove too much material. I resorted to do this the slower put more precise way with various metal files. It comes in handy to use a file that has a "safe" edge on one side as to avoid cutting/filling into the tang or edge.
I also removed any burrs that were left over from the previous step.
Step 9: Prepare for Drilling
I decided to have a total of four pins to connect the handle to tang/blade. The distances of the four holes are roughly 2cm between each other in the center of the tang.
A center punch was used to make a series of small indentations which would later allow the drill to make a hole at the correct spot without wandering/slipping over the tang.
Step 10: Pilot Holes
Using a 4mm HSS drill and some cutting oil I was able to create four clean pilot holes quite easily. I highly recommend to use a drill press for this step if you have one to ensure straight holes.
Step 11: Enlarging the Holes
I immediately followed the previous step with a 6mm HSS drill to create the final size holes for the brass pins. If you are planning to use large pins I would still recommend to increase the hole diameter in increments if possible. Each would only require the drill to remove small amounts of materials at once which makes things much easier.
Step 12: Material Selection for the Handle
I had this rough processed piece of oak in my shop that was used as an improvised shelf on top of a radiator by its previous owner. Since I didn't wanted to waste too much of this material I created a template for the handle design and used it to measure the length of material I needed to cut.
Step 13: Make the First Cut
For this and most of the following cuts I used my Metabo miter saw. You could use whatever saw you have for this though. It is a simple crosscut so a hand saw would suffice just as well as a table saw.
Step 14: The Second Cut
This was a rip cut and although my miter saw can extend quite a bit I had to flip the piece over once the get the cut done. Looking back I was simply too lazy to change the setup for this scene although using my circular hand saw would have been the better choice. If you have a table saw the choice would be easy for this quick rip cut.
Step 15: Was This the Right Choice?
Well yes and no!
I did make this cut too early and I will explain why in a few moments.
As far as the choice of the tool I would have preferred to do this with a bandsaw but since I do not have one I resorted to my miter saw. This had the benefit that the saw blade had the same thickness as my blade had. The drawback was that due to the circular shape of the miter saw a gap was created that was larger than the tang. I will explain how I tried to correct this in a later step.
Step 16: Preparing the Handle for Shaping
Here is a trick I've learned from Izzy Swan:
If you want to glue a template to a work piece you should first stick some masking tape onto it and then use a glue stick to attach the template. This makes the cleanup much easier since the tape can simply peeled off without much glue residue to clean up.
This works for most materials and surfaces that masking tape can stick to.
Step 17: Rough Shaping the Handle
I wished once more to have a bandsaw for this step but to be honest a jig saw did the job just fine.
Staying outside the outline of the template whilst removing as much material was key in this step and requires a little practice.
Step 18: Drilling the Pin Holes
So here is the step that I should have done earlier!
I should have done this step before I made the slot for the tang but missed to do it in the rush.
A little trick to make this work is to use cut-offs from the blade as spacers to keep both parts space apart at the correct distance. I then clamped the blade into position and drilled the four pin holes without any issues.
Step 19: Shaping the Handle
Now there are many ways how you could achieve this and I really can't say which is preferable. For my part I used my angle grinder with a 40 grit flap sanding disk. There are other grits available but all I wanted for this step is to remove lots of material quickly. Since I can not adjust the speed I had to be extra careful and use the grinder without pressure doing only light passes checking the work piece after each one.
The main objective here was to round over the corners and get it into the general shape.
Step 20: Refining the Shape
Once I reached the level of detail I desired I continued to refine the shape using a belt sander, files & rasps as well as several grits of sandpaper.
Since the theme of this project is set in a post apocalyptic scenario i decided to keep the look a bit rough and not too polished.
Step 21: Polishing the Blade
Although I didn't wanted a highly polished look I decided to at least remove the rust and some tool marks from the surface of the blade & tang before the glue up.
I used the belt sander for this step and chose a relatively course belt (120) to "polish" the surface.
Step 22: Marking the Center
This step is important to prepare for the bevelling of the blade.
First I used my calipers to measure the thickness of the blade. I divided this measurement by two and adjusted the calipers to that value.
Secondly I used a permanent marker to paint all edges black that should later get a bevel.
The tips of the caliper can be used as scribes by guiding it along the edge. Do this from both sides of the blade and you should end up with either two or with a little practice one line that marks the center of your blade.
Step 23: Rough Beveling
For starters I used my large bench grinder and a piece of wood that was cut to an angle of 25°. Do not clamp the angle to your tool rest! This would cause the work piece to be pulled between the tool rest and the spinning grinding stone. This could result in injury, damage to the tools and/or work piece.
You should chose angle that is appropriate for the tool/knife you are making. Although opinions differ the angle I chose is comparable to what you might find on a bushcraft or hunting knife.
The large bench grinder takes off a lot of material quickly so I had to be careful with each pass and check constantly. This also helped with keeping the blade cool to avoid ruining the temper.
Another thing you should be aware of is that the shape of the grinding wheel will create a hollow grind on your blade. This can be a good or bad thing depending on what your intentions for the blade are. A hollow grind can be extremely sharp but will create a relatively weak edge. I will address this issue in one of the following steps.
Step 24: Refining the Bevels
I transitioned to my smaller and less powerful bench grinder to refine the shape once I was happy with the initial bevels.
This step helped me to define the bevels and prepare the blade for the hand beveling in the next step.
Step 25: Finishing the Bevels
I decided to finish the bevels by hand to achieve as much accuracy as possible.
This was done with a set of metal files and a simple wooden angle that helped a lot with maintaining consistent angles. There are a ton of great jigs out there for knife makers to create perfect bevels using no power tools at all. I intend to try some of them out one day.
Opposed to some of the other steps of this project I took my time with this one until I was happy with consistent bevels all around. As I've mentioned before the bench grinders created hollow grinds but with some file work I was able to turn that into a V grind that is stronger than a hollow grind.
Step 26: Polishing the Bevels
To remove the file & tool marks I used a small belt sander with a 180 grit to polish the bevels. This also had the benefit of removing any burrs from the previous file work.
Alternatively this could be done with progressively fine sand paper grits and stones.
Step 27: Sharpening
For this step I used a small wet stone since I felt that the shape was a little too complex for a large stone (At least for my skills). Since this project will mostly be a show piece I didn't aim for razor like sharpness but this could be achieved if that was an objective.
Step 28: Prepping the Pins
My choice for the connecting tips was some 6mm brass tubing.
I roughly estimated the required length and cut them to size with a hacksaw. Since this left some pretty ugly tool marks I polished the ends up with my little belt sander.
A step that isn't shown in the pics or the video is that I chucked the brass rods up in my drill and "test fitted" them in their later positions.
Step 29: Glue Up > F*** Up
Ok I admit it this is where I really messed up. That day was a bit too much and I tried to get the project finished in a hurry. This caused me to skip the important part of properly masking up the blade and handle with masking tape. This tape would have prevented the epoxy to stick everywhere which caused some lengthy clean up.
Anyways I mixed both parts of a 5 minute two component epoxy and covered the tang evenly. The tang was then inserted into the slot in the handle and held in place by two pins...
Step 30: Glue Up Continued (later)
I was lucky that I was able to fit two of the pins thus fixing the blade in place. I had to slightly enlarge the holes for the other two pins and inserted them without any further problems.
What followed was some time to cure and lengthy clean up of the epoxy that had gotten to places where it should have gotten to.
Step 31: Fill Gaps
I mentioned before that the circular saw created a slightly larger slot than what was needed. This time I took the time and masked the handle of with some masking tape and filled the gaps with some more 5 minute epoxy. Working the the epoxy into the slot with a coffee stir stick worked quite good and I was able to remove most of the air bubbles. Maybe a pourable resin would be a better idea (Suggestions anyone?)
Step 32: Trimming the Pins & Flush Sanding
Since I made the pins a little longer than needed for easier handling I had to cut off the excess bits with a hacksaw. Again a bandsaw would maybe be a better choice but I won't complain.
I followed this up by sanding the areas flush on my belt sander although some sandpaper on a sanding block would do just fine.
Step 33: Finishing the Handle
The handle received two coats of a beeswax & linseed oil mix which was polished up later.
Step 34: Deburring the Pins
Late into the project I noticed that the inside of the pins also needed some more work. In this case I used an 8mm HSS drill and slowly removed any burrs that might have been created by the previous sawing & sanding. One of the pins also had some epoxy inside which was removed with an awl and a pass with a 4mm drill.
Step 35: Handle Wrap
For the handle I decided to go with a simple paracord handle wrap. I found a great Instructable that details the how to so I strongly suggest you check it out.
I followed the authors advise to use clamps every now and then to hold the cord to rest and to drill a 8mm lanyard hole into the end of the handle.
Once the wrap was finished I passed both ends through that hole and secured it with a figure 8 knot.
Step 36: Finished at Last
Right this project was finished over the course of three days but I guess this was also due to a lack of experience, parallel filming of the project, learning from mistakes etc.
So with a little more practice and preparation I guess this could be done within a day or two.
Once again the blade wasn't heat treated since it was made from already tempered high speed steel and since I do not have an appropriate setup to heat treat such a large blade.
Make sure you also check out the other projects made for this challenge here on Instructables and on YouTube.