3D Printed Sheath for 8-in Chef Knife

I was recently gifted a new Shun knife without a sheath.  Obviously, I did what any normal person would do – I designed my own custom 3D printed sheath.

The perfect cover, a 3D printed sheath for my chef's knife.

The Design

The original design is based on the Shun DM0706 Classic 8-Inch Chef’s Knife. The curvature of the blade is similar between knives, and the hollow portion for the blade was given ample room to accommodate other variations. The opening of the sheath is directional, there is a simple clasping architecture to hold the sharp bits in place. For my print and my knife, this is very tight, which is what I wanted. It takes some muscle to unsheath the blade, making it a bit more child/idiot-safe.

The blade fits tight the custom opening.

An external comparison.

This wireframe image lets you see how the interior of the sheath is shaped.

The Pizzazz

I wanted to add a little something extra to the design of my 3D printed sheath, so I decided to add some lettering.  As I have more than one Shun knife with very similar handles, I added some lettering to denote that this was a 3D printed sheath for a chef’s knife.  So, I created some raised letters on the edge of the sheath which read CHEF in a narrow Impact typeface.


I’m quite happy with the design.  The curvature has a nice exotic feel to it, and the lettering adds that extra “something”.  I am very happy with how tight the fit is for the blade, as I like to feel secure that the knife won’t be slipping free any time soon.  My other Shun knife is responsible for a non-trivial flesh wound, so I am especially concerned for safety with these amazing extra-sharp kitchen razors.

The Part

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

Just want to try the parts out for yourself?  The  .stl file you will want to download is below.


DIY Bone Conduction Headphones

EDIT 07/18/17: This post has been getting a lot of hits lately. Since I don’t have comments enabled for my site, if you have questions or would like to comment on anything, please feel free to email me directly. My email can be found on my CV (I won’t post it here so the spam bots don’t eat me!)

I discovered something fascinating while browsing around the other day: headphones that transmit sound directly to your skull.  This method of sound transfer has been dubbed bone conduction.  All you do is press the little transducers up to your temple, jaw, or skull, and the vibrations in the little electrical device transfer to the waves through the solid bone medium to your inner ear.  This way you can listen to things without blocking your ears with big cans or buds.  Rather than go out and purchase one of the little premade units, I decided to make my own DIY bone conduction headphones.

I have my own issues with headphones.  I am the type who strongly prefers earbuds.  Sure, you can get better sound out of headphones, but I find that the large strap and bulky padding smashes my ears and glasses together in an uncomfortable way.  Furthermore, the shape of my skull with causes the applied pressure of the headphones to pull my glasses out of alignment.  That puts pressure on one side of my nose or the other, and it makes my vision all out of alignment.  To make things just that much worse, my very fine hair is easily molded, a quality that makes it easy to get ready in the morning but causes instant hat hair.  Headphone bands give me this weird wave in my perfect, voluminous follicle coif.  If you look at the bone conductivity headphones available on the market, they all use a strap to keep them in place like a normal pair of headphones.  With the extra pressure required to push the transducers up to my jaw, I can only imagine that they would have even more issues.

So I thought to myself: how can I make a set of DIY bone conduction headphones with properties closer to earbuds?

Answer: use the straps that you wear every day, your glasses.

The Build

For this build, I purchased equipment from Adafruit which was very similar to the stuff recommended in the Ruiz Brothers build.  I used

I followed the build similar to the Ruiz Brothers instructions linked above with substitutions made for the parts I sourced elsewhere, such as the battery pack.

I glued the completed breadboard to the battery pack and called it a success.  My first tests (using the transducers on my apartment’s door to introduce my partying neighbors to Norwegian black metal) proved the build to be a success.

For future modifications to this, I plan on soldering a jumper on the gain pins instead of using the removable jumper.  I also would wire the headphones directly to the board rather than using the European headers included with the breakout board.

The amp circuitry and transducers for the DIY bone conduction headphones.

The Buds

As you can see in the picture of the build, there are these strange brown boxes wired to the device.  These are the containers for the bone conduction transducers.  These were designed in Fusion360 to fit the transducers quite snugly.  The Adafruit page offers a technical drawing of the transducer, but I found that my units were slightly off of this specification.  I wanted the transducers to fit in the housings without much room to rattle and lose volume and quality, so I went with my measurements.

These are the housings for the bone conductor transducers.

The hooks on the end of each housing are designed to fit onto the earpieces of my glasses.  The plastic glasses I wear have a slightly tapered profile.  This means with a little push of the parts onto the earpieces, they stay in place without sliding off.  The inside of each of the hooks on the housing are slanted, e.g. one end is more open than the other.  This means that the housings are not interchangeable, and fit on either the left or the right side of the glasses.  The cover of the housing fits into the remaining room around the transducer and these can be glued into place.  The slit at the bottom provides enough room for my cheap wires to go through or a bit bigger gauge if you are concerned about sound quality.

The parts fit onto the earpieces of my glasses.

The housings were printed on a Makerbot 5th Gen in dark brown PLA filament.  The print was scaled at 102.4% from the actual design size.  This scaling was based on a previous calibration curve of the printer PLA shrinkage and print accuracy.  Like I said, I wanted the tightest tolerance the little 3D printed parts could manage.

The little widget below is clickable, and it will let you move the 3D object around to see for yourself how it is designed.

This is the “left” container.

This is the cover which fits over both the “left” and “right” versions of the above model.

Just want to try the parts out for yourself?  The three .stl files you will want to download are below.






The Fit

With my little DIY bone conduction headphones complete, it is time to try them out.



A handsome man with his DIY bone conduction headphones

Look at that handsome fellow in the picture.  The transducer housings fit as expected on my glasses.  The sound transferred well to my skull.  If you have ever used bone conducting transducers before, think of it like a medium press sound transfer rather than a super hard press.  The brown color is still stands out a bit from the color of my glasses and my hair.  Finishing paint would be necessary to make it look nicer.

The sound quality was pretty good as far as these little transducers can go.  They won’t be replacing my in-ear monitors any time soon, but they are sufficient to listen to spoken word audio.

Bonus trial: my mother is partially deaf due to Meniere’s disease.  She tried my DIY bone conduction headphones and was able to hear things on better on her deaf side.  Further development of this technology may prove to be useful for sufferers of mild hearing loss who do not desire the full hearing aid.

The Purchase and Return of a Makerbot Replicator+

Minor note: I got my PhD the other day.  No big deal.  The important part of the story is that I got a sweet graduation present from my mom.  She bought me the 3D printer of my choice.  Talk about awesome!  I decided to go with a machine I have had some experience working on/with in the past, a Makerbot.  There were a lot of options out there, and some of those alternatives had pretty great reviews.  I decided to go with the latest Makerbot model.  It wasn’t until I had gotten up and running that I became aware of some of the major Makerbot Replicator+ issues.

The Good

Before I really hand a chance to grasp the Makerbot Replicator+ issues, I had a lot of fun with the unit.  The setup was a breeze and I was printing as soon as the extruder warmed up.  In addition to some of my own designs, which I will give individual attention later, I printed off designs that are easy to find on the Thingiverse site.  My favorite print was a fully articulated pangolin.
Save the Pangolins
Save the Pangolins from the side

This cuddly little creature was produced as part of a project to raise awareness about pangolin exploitation, the most trafficked animal in the world.  There are some poorly educated people out there that believe that the pangolin scales have magical healing powers.  Additionally, they are a very popular bush meat item.  Despite being illegal to buy and sell in many parts of the world, the ever wonderful homo sapiens manages to make a buck from these little mammals.  The Save Pangolins campaign aims to eliminate this illegal trade.

The print itself turned out quite well.  This was the first big print on the Replicator+.  The details came out fine and it feels quite nice.  I did have some issues getting everything perfect.  The final tail joint and the forelegs did not articulate.  This print was made before I had started fine tuning settings like extruder pull, so some stringing between these tight joints may be the cause.

The Bad

I discovered that when printing flat surfaces, I would see some bizarre defects.  The layer deposited on the surface would form melted waves.
Waves from the side

I printed off some test swatches and observed them.  The extruder head was dragging along the edge of the recently printed strand of the current layer.  This was causing the last few printed lines to begin to curl with the direct heat transfer from the extruder.  The weirdest part was that it only happened in one direction.  As layers were stacked, the Makerbot Replicator+ issue would only propagate along the X coordinate.  If a layer was printed in another direction, no issues:
A flat surface

Here is a side by side comparison of what the issue was:
Side by side

Something was clearly not right with the setup of the printer.  In the true spirit of Maker culture, I decided to find a solution to the problem.  I told the printer to recalibrate the z axis.  If the printer head was dragging along the side of a print, it would make sense that the printer bed height or z axis motion was out of whack, right?  That is when the real problems started.

The Ugly

On the first print after issuing the factory supplied z axis calibration command, all hell broke loose.  During the setup for the print, the extruder dragged along the edge of the print surface.  I rushed downstairs to stop it as soon as it had started.  The scraping made some gruesome noise.  Meanwhile, the extruder continued gouging into the print bed.  The hot extruder nozzle actually melted the plastic as it scraped itself across the surface.  I did not make it downstairs in time though.  When I got downstairs, the printer had ripped the extruder out of its mount and began making panic noises.  The scene wasn’t pretty.

These are the real Makerbot Replicator+ issues, self mutilation

I sent a complaint to the manufacturer about my Makerbot Replicator+ issues.  One of my favorite snippets from that little conversation was that the end users are not supposed to level the build plate despite the fact that the option was included in the software.  The factory levels those “with lasers”.  To their credit, the customer service rep did offer to replace the unit.  This was not enough for me.  I was already soured on the unit when I couldn’t get it to interface with any of my computers, since they apparently dropped Linux support.

Now I’m awaiting the RMA results.  Besides wasting my time and getting screwed out of 10% of the unit cost for a restocking fee, I’m just plain disappointed in how far the genericized flagship of 3D printing has fallen.  I can only hope that I’ll be happier with the Ultimaker I buy when the refund goes through.


A 3D Modeled Keyboard Cap

After I got hooked by the allure of 3D CAD, I decided to practice my skills by making a 3D modeled keyboard cap.  I started working on something using OpenSCAD, but it proved difficult to get the sort of organic curves I wanted.  I wanted to get some experience using a GUI based-program, rather than just scripting.  Instead, I decided to try a program called Fusion360.  This program is a free variant of Autodesk for personal and low-impact use.  It sadly does not have a Linux build, but I have had luck with it on my Windows box (it has the more powerful gaming GPU’s on it anyway).

The Design

I based my design on the classic caps you would get on retro units, like the Commodore.  A modern variant is available from Signature Plastics (PMK) known as the SA profile.  At the time I originally made this model (April 2015), there weren’t any of these models freely available.  This should be similar to the SA keycap dimensions but not quite the same.

The 3D modeled keyboard cap from the side.

The 3D modeled keyboard cap from the bottom.

The Real World Versions of my 3D Modeled Keyboard Cap

I decided to have these 3D printed from a commercial vendor, rather than trying to print it on a home printer.  I wanted to get some better detail.

The first print.

The height is somewhere between Signature Plastic’s DSA and SA row 3 profiles.  You can compare the shape and size in the picture below of my 3D modeled keyboard cap  to a DSA (left, in black) and an SA (right, red) profile cap:

A comparison of the print to commercial versions.

I’m glad I did this test run.  The stem shrank in a way I didn’t expect, and the cruciform is a bit too big.  It slips on and off the stems too easily.  This is an easily fixable problem.

The bottom side.


I made a new version with a tighter cruciform.  I added some text on this one.  Nothing like a little American Psycho quote to brighten up a keyboard.  I ended up giving this to a colleague as a gift.

Feed me a stray cat.


If you would like to use this file, feel free to do so.  Check it out:

This is a 3D render, play around with it!

And here is a download link.