Want to make a gift that has double the charm by being homemade-with-love combined with being punny?
I introduce the Cherry Pi knives. A knife cut out of cherry wood, used to divide pies, and decorated with the Pi symbol to remind everyone of its purpose.
Wooden knives my not seem like the most useful thing in the world but they are actually really nice for soft foods such as: pies, cakes, soft cheeses, and many other baked goods. They guarantee that you won't scratch up bakeware or cut through foil pie trays. See! They are handy even though it may not be the most used utensil in the kitchen.
I would like to share my techniques and little things I discovered making these knives so you can make sets of your own! This is a fairly quick project that can be done in about 30-45 min per knife so I hope you'll try your hand at it.
Materials and tools:
Belt sander - mine is a cheap one from harbor freight, if I can make these on that anything should do!
Cherry wood (1/4" x 2" x 24")
Laser cutter or scroll saw/bandsaw
220 grit sandpaper
Food safe mineral oil (cutting board oil)
Step 1: Design and Cut Out Your Knives
I bought a slab of cherry wood (1/4" x 2" x 24") to cut my knives from. I was assured cherry wood is a food-safe wood and it helped add as many levels of pun to this project as possible. All good things!
I designed my knives in Illustrator, making sure I maximized the number of knives I could cut per board so everyone in the family could get one! (I have a small family). I prepared my file so I could have my knives cut with a laser but you could easily print out the design and use it as a template with a scroll saw or a bandsaw.
I have provided my file free for use. Let's fill the world with Cherry Pi Knives!
I wish I had pictures of the laser cutting process, maybe next time I get a set cut I'll get my laser cutter tech to take some pictures for me that I can add.
Step 2: Grind Down Your Edge
This knife has some very interesting differences in grinding down an edge from wood that you wouldn't run into grinding an edge from steel.
- Wood grinds down much faster than steel so you can get it shaped in about 15-20min. That's about 1/4th the time it would take to grind down a similar knife edge on a similarly sized knife.
- Mistakes happen quickly and are harder to fix. I quickly learned to have a lighter hand to eliminate the chance for accidental gouges. Steel is much more forgiving with mistakes.
- Knots create a problem. Since the knots are a denser wood they take longer to grind down. You may find you need to focus more pressure on those spots keep your knife blade from getting misshapen! Preferably you'd want to avoid knots on the blade but I honestly didn't even consider it at the time.
- You'll want to keep the blade thick.Wood has a little bit less stability than steel so you'll have to keep the blade a little thicker throughout. I ground a sharp edge, but kept the top edge of the blade at 1/4". That'll give the blade enough strength to not splinter apart with use.
Beyond the tips I shared above, I used standard knife grinding techniques. There are countless ways to grind a knife accurately and I personally work by watching it closely and adjusting as I go. Those will be the techniques I will share for this project, feel free to browse other instructables for more knife making tips.
Remember, these are going to be made with love, not factory precise!
Pull the knife blade across the sanding belt using consistent pressure and speed. For a food knife you'll want a pretty shallow angle in order to have the grind to make it all the way to the spine of the blade while forming a sharp edge. I start at a pretty medium angle and watch it form an edge inward so I can set a good angle to follow. I will gradually make the angle more shallow as I begin to sharpen the edge.
Alternate grinding sides. I'll do 5 passes on one side, then switch and do 5 passes on the other. This ensures you grind the edge down to the middle evenly as well as makes you stop and check for any mistakes or any adjustments you need to make before they get too big.
Check the grinding distance as it travels down the width of the blade. This is a good indicator that you are grinding evenly along the edge and that both sides are getting ground down at the same rate.
Check the knife edge for uneven thickness or leaning. If you find a bulge or a thin spot starting to form you may need to adjust your speed or pressure at that point in the blade. If you encounter bulging, slow down or add pressure. For thinning, try a lighter hand or faster passes at that point. You'll notice your blade leaning if your edge is starting to form off center. This happens if your angles aren't matching or you are grinding one side more than the other.
Fix any errors you catch. As you find errors, simply adjust your technique until you have things even again. You can try carefully grinding a bulge down, taking a few extra passes if one side is leaning, or doing some light passes to correct a gouge.Patience and diligence are your best friends in edge grinding-keep at it and don't let errors discourage you!
Grind until you have a sharp edge and has been evenly ground back to the spine of the knife.
Step 3: Sanding!
Sanding will turn your knife into piece of art!
I used 220 grit sandpaper. It was admittedly a little slow to get out some of the deeper marks left over from the belt sander. If you have stubborn scratches or cuts I recommend starting with 180 or 200 grit sandpaper instead. For finishing, I don't think anything higher than 220 grit is necessary.
I worked the sand paper along all the edges to remove the charring from the laser cutter. I also took the opportunity to round the edges over with the sandpaper so that the knife feels comfortable in your hand. Finally I sanded down the faces and blade of the knife until all scratches were removed and it felt heavenly smooth.
Step 4: Let's Protect Our Wood!
This is by far the most satisfying part as the oil just makes the wood come to life and really showcases all of your hard work. Oiling your knife will protect it, keep it food safe, and make it look entirely professional.
Before you start oiling you'll want to make sure you have removed all the sawdust we created with our sanding. An air hose would be the best option, a microfiber cloth would be second best. If you don't have either of those on hand you can use any clean cloth or a paper towel and the power of your own breath to try and dislodge dust from the cracks.
Finally, we've made it to the end. Oil the entire knife with food safe mineral oil (cutting board oil). I simply followed the instructions on the bottle: apply oil liberally using a paper towel or cloth, let oil soak in for 45min, then wipe off excess.
I made a huge mess and got oil everywhere, so perhaps you'll do well to put down some plastic or newspaper before beginning this step. Perhaps others are more clean than I am but I swear that oil magically ends up everywhere.
Step 5: Taking Care of Your Knife
Your newly hand-crafted knife is made out of wood and that tends to make it a bit fragile compared to other kitchen utensils. Here are some tips to consider for the lifetime of its use.
- Hand wash only! A dishwasher will, simply put, obliterate your knife. Dry immediately after washing
- Re-oil periodically. If it seems to be getting dull or water logged, try giving it a fresh coat of oil. In extreme cases you can sand it a bit first, then re-oil.
- Avoid cutting things that are less than soft. It is a thin wooden blade, it will break if you try to cut a steak.
- Most importantly! Enjoy and have fun :)