CNC Milled Bit Box

Based on my newfound love for CNC milling, I decided to make a CNC milled box for my bit collection.

The design went through a few different iterations, some with hinges, some without, some made of metal, and yet others made out of acrylic and wood. The final design I settled on would be made of wood with a pair of protruding lips on the base with accompanying slots on the lid. The fastening mechanism would be four pairs of small magnets that are concealed by small aluminum tabs, mechanically fastened to the lid and base. The bit slots would be milled using a ball end mill in addition to a couple of finger slots to get it open.

This piece of wood gets a second chance to be something!

My first attempt was to use the oak from my failed first dovetail project. Very quickly I learned that this was not a great idea. Oak is a pretty tough wood, and it was also not perfectly flat. This prevented the wood from sticking to the spoil board even with ample tape. As soon as I started cutting, the wood was off the board and the cut ended itself.

Really test whether your material is stuck to the spoil board. If you can easily move it, so can the mill.

Even though the job failed, my bit survived! Phew.

I decided to switch something a bit more reliable: plywood. I had a thick piece of plywood that I thought would do well for this project. The milled piece looked good enough, although the thin top veneer layer looked a bit shabby. I also had to end the cut early as my bit wasn’t tall enough to cut the piece all the way through. Not a problem though; there was enough surface area on the sides to come back with the hand router and finish the edges after roughly cutting it out with the band saw.

Band saw to the rescue!

Upon further inspection, I found that the piece was cut totally wrong. I checked to make sure all of my files were coming in correctly, and confirmed that they were. I realized after just examining the machine that the tool head wasn’t in the same place that the software thought it was! This led to my 2nd major lesson of the day:

Always be re-homing.

The app and the machine couldn’t agree on where the bit was.

I decided to switch gears and materials and begin working on the aluminum tabs. Shortly after I had begun, I saw that the software informed me that it would take 3 hours to make them! This was pretty disappointing, but I really didn’t have time to run this job for three hours. I switched over to acrylic instead. The acrylic was significantly shorter and still worked.

Acrylic is pretty versatile in the mill.

When I finished the acrylic, I went back to milling the body of the box and this time used some Baltic birch I found. It milled much better due to the thicker veneers. I was also extra careful about making sure the machine was re-homed between each part of the job.

Baltic birch is also great in the mill.
I had to shave a whole 1/16″ off the top to have the two lips stick out.

One thing I conceptually understood but really failed to fully grasp was that in subtracting material, any appendages or limbs really are time-consuming to make. It means that all the material around that bit needs to be removed. The top of the box ended up taking twice as long to mill as a result.

When I finished milling the plywood, I put the magnets into the holes I milled out for them. It turns out the tabs were completely unnecessary. The holes were a bit snug and ended up gripping the magnets tight enough to keep them from pulling out. They were also strong enough to only require two of the pairs instead of the four I planned on using.

Base and lid with magnets placed in tab slots.
The plywood parts of the box fully assembled.

The edges of the box were a bit sharp, so I decided to go back to the hand router and use my 1/4″ rounded bit to get a nice round corner, something that would be possible with the other mill but probably very time-consuming.

It took 10 minutes to round the corners perfectly.

I then decided to put a face plate on the top in order to identify the top and bottom. This was pretty unnecessary, but it didn’t take too much time. I milled out an 1/8″ deep rectangle that I could inset another piece of acrylic which identified the kind of bits are inside.

I think I’ll try larger text next time.

I ran into some issues trying to engrave into the acrylic fine text, so I ended up doing the last piece on the laser. Its maybe a bit too faint, but I like black on black. To finish it off, I used stainless steel counter-sunk wood screws to hold all the plastic in place. Final shots below:

I’m pretty satisfied with the end product and might try some of the finishing techniques we went over in class. It would look great with a wax finish to make it less rough. While I feel pretty well acquainted with the othermill, I’m also aware of its limitations. When I was trying to engrave the face plate, I realized that the software prevents the milling of open polylines. I had hoped to engrave single line text like I had done using drawing machines. I suppose this is helpful for making PCBs but really annoying otherwise.

Here are some additional figures from this experience:

  • 3 vacuum batteries
  • 3 different kinds of bits
  • 4 different kinds of material
  • 2 failed pieces of wood

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