Hi Instructables Community,
this week I'm showing a project that I've wanted to tackle ever since I made my "Mini-Survival Knife from an old Saw Blade". Since the rest of the saw blade was still siting around in my shop I decided to give it a go with the things I've learned in that project.
I must say that overall this has been the most satisfying project so far. Both in terms of skills & techniques tried out as well as the final video edit this whole project came out way better than I've hoped for.
You can also use this link to get to the video directly (Using this link also gives my channel more clicks than watching the embedded video).
If you liked this project make sure you subscribe here on Instructables and also to my YouTube channel (Where you can watch my projects usually a few days before the Instructable is published).
Step 1: Drawing and Preparing a Template
First of all you have to decide upon a design to use for this project. You could of course try to improvise on the fly but the results won't be as good (or consistent) as with the help of a template.
I usually have a "Brain dump" (Check this link to Andy Birkey who explains this in under a minute & while you are there you might as well subscribe to him since he deserves far more subscribers) with me to write down ideas and sketches for project ideas. One day I happened to come up with a relatively simple design (see attached file) for a broadhead arrowhead.
I scanned & copied this design six times to a regular A4 sheet of paper which I then cut with my circular cutter and scissors. You recommend not to cut right down to the outlines since you will want some "meat" later on for grinding and shaping.
Step 2: Preparations
I actually cut out all six templates and tried around for a while to see how many arrowheads I could get out from that old saw blade. It turned out that there was enough material left to comfortably make four arrowheads.
Using a straight edge I divided the saw blade into four segments and marked them with a permanent marker.
Step 3: Don't Be Stupid (Like Me!)
I must admit that I was a bit too enthusiastic to get this project going so I took a shortcut that could have caused some serious damage to my fingers/hands. Since my workshop is still in a very improvised state I couldn't (Or was too lazy to) properly clamp down that saw blade. I tried to hold it down with my fingers while paying attention to keep them parallel to the 1 mm abrasive blade in my angle grinder while cutting slowly. While working I was pretty confident that with sufficient care being taken all should be fine. But during the video editing I realized how close the fingers really where and how quickly something could have gone wrong. Don't be lazy like me!
I recommend to make a simple jig with a toggle clamp or use some other clamp to hold it firmly during the cuts.
Step 4: Glue on Templates
Now simply use a glue stick or some spray adhesive to glue the templates to the steel segments.
You could also use some quality masking tape to make the removal of glue residues a little easier in the later steps. Simply put some masking tape on the steel and the glue the template onto the tape.
Step 5: Rough Shaping
For this step I used my angle grinder with a 1 mm cut off disk. Clamp the work piece down and move closer to the outline while removing as much material as possible without actually touching the outline. To avoid long cuts I recommend you do a series of relief cuts which will make the material removal much easier.
Step 6: Shaping
To remove even more material and moving closer to the outlines I used my large bench grinder. I tried to get within 1mm the outline or on the long straight edges even closer.
Since this beast is taking off a lot of material quickly one should be extra careful and keep some water nearby to cool the work pieces regularly.
Step 7: Marking the Relief Holes
Since the paper templates got wet during the previous step I was worried that they might become loose so I did this step a little earlier than I otherwise would have done.
The objective here is to use a center punch or auto punch to make small indentations. In a later work step this will make t easier to drill holes through the steel without wandering off.
Since the steel wasn't annealed at this stage it took a few taps with the hammer to create proper indentations.
Step 8: Refine Shape
This step requires you to take your time and use your tools wisely.
With the arrowheads firmly clamped down I used the angle grinder to remove more material from the inside of the barbs. You have to be very careful here and don't try to get directly to the outline.
Next I used my smaller bench grinder to move onto the outline wherever I could. Since the grinder isn't that powerful it is relatively easy to control the amount of material that is being removed.
For the details and hard to reach places I used various files until I was happy with the overall finished shape.
Step 9: Annealing
To soften the metal for the drilling I attempted to anneal it by heating it up with my propane torch. You will have to be careful here not to overheat the work piece or expose it for too long to keep oxidation (and scale to a minimum).
Step 10: Drilling the Holes
I decided to add two holes in the design to allow for flexible attachment options. Not shown here or in the video is that I've tried to drill a pilot hole before the annealing which however failed resulting in a broken drill bit.
After the annealing I started with a 2 mm drill on high RPM with little pressure. I've also added a few drops of cutting oil. After a few seconds I could see that the drill bit into the indentations and widened them for the pilot hole.
I followed this up with a 5 mm drill which went trough quite easily (So no need for a smaller pilot hole in this case). To remove the burr I used a 7 mm drill but you could also use a hand de-burr tool for this.
Step 11: Preparing a Grinding Jig
Using a miter saw I cut off a piece of wood at an angle of 25° on one (Long) side.
The bottom of this piece was sanded flat before to ensure that it will run smoothly over my tool rest.
Next I used screws to fasten all four arrow heads to the angle.
Note: Make sure that the flat edges for the arrow heads are flush and parallel to the bottom edge of your jig.
Step 12: Grinding the Bevels
With the jig from the previous step it was very easy to create consistent bevels on all four arrowheads. Since they were all mounted at the same time this was a super time saver.
I opted to use my small bench grinder since it is relatively forgiving and yet powerful enough to remove material quickly.
Step 13: Deburring
To remove burrs from the non-sharpened parts of the arrow heads I used various small files. You could also use sand paper for this step but make sure it is attached on a flush surface. Another option would be to use a manual deburring tool
Step 14: Hardening
Since I wasn't sure exactly what kind of steel I was dealing with I did a few tests beforehand with some of the cut offs. These tests (Spark test, filing, hardening & shattering) led me to the conclusion that it should be possible to harden the steel.
First I heated the piece to a red to orange glow and quenched it in water. I tried to use a file in the hardened areas but it skipped over the surface which led me to the conclusion that the hardening should have been successful.
The steel is now very hard but also brittle which is something that we will address in a moment.
Step 15: Removing the Scale
The previous step usually results in surface oxidation in the form of scale (The hard ugly cousin of rust). This scale should be removed for various reasons so grab some sandpaper (preferably a lower grit that can be used for wet sanding) and glue it to a flush surface (such as a pane of glass).
Add some water or soapy water and begin to polish the faces of the arrowheads until both sides look like they have an even surface.
Moving the work piece in a figure 8 should ensure even sanding.
In the last picture you will notice that the surfaces might not look uniform. This was a reminder of the previous live of this saw blade and are tool marks.
Step 16: Tempering
As described in a previous step the arrow heads are now very hard but brittle. To relieve the stress from the material we are now heating it up to 200°C (392F) (This is the max for my shop oven). If you know exactly material you are working with you can look up its exact tempering temperature. I left it in the oven for 1 1/2 hours and let it cool down slowly in the air after that.
Ideally you are exchanging some of the hardness against increased toughness.
Again the more accurate you can do this the better your results will be.
Step 17: Polishing & "Sharpening"
Next move on to polish the arrowheads using wet sandpaper on a flush surface (e.g. glass).
You can go as high as you like but since I have something else in mind I only went up to 400 grit to remove any oxidation caused in the previous step.
I also used the sandpaper to remove the burrs from the cutting edges. Using my finger as a guide/rest I was able to sharpen the edge to a nice uniform sharpness. I didn't want the edge to be razor sharp though since it would be too susceptible to damage when shooting it.
Step 18: Blackening/Blueing
To protect the blade from rust I decided to try a treatment I saw in a YouTube video not long ago. You could also use commercial blackening/blueing products or improvise this with hot vinegar or mustard. The idea is to create a protective patina in a controled way to prevent uncontrolled oxidation (rusting)
I went with the hot vinegar method and highly recommend to do this outside or in an well ventilated area. I heated the vinegar in a metal cup and poured it into a glass container in order to observe the process.
After five to six minutes a dark grey layer had formed and I removed the arrowheads and quenched them in water to neutralize the vinegar.
Step 19: Oiling
For additional protection I applied a very thin coat of Ballistol Multi-Purpose Oil.
Step 20: Preparing an Arrow
I had an old broken arrow in my work that was used for target practice and had a broken field tip.
I used my Japanese pull saw to create a slot for the arrowhead. With a file I created a chamfer on the end and spread some glue onto the shaft and tip and then tightly wrapped it with strong leather sewing yarn. I started this wrap with a constrictor knot and ended it with one securing it with a stopper knot. I then applied some additional glue on the wraps to seal them.
Step 21: Testing
For the testing I used my underpowered sling-bow (Inspired by the Slingshot channel) which features an arrow guide and some paracord to nock the arrow.
The distance this time was well bellow 10 meters and it became clear quickly that I will need more practice but the tip held securely on the shaft and maintained its edge quite well.