Wooden Espresso Knock Box

Turn a utensil container into knock box. Way better than banging your portafilter in the sink, and cheaper than a retail one.
This method can be used with any container with a wall thickness of .5" to .75"
I used my wife's "Giadia Bamboo Utensil Holder" This has a wall thickness of .75"
A big section of pvc pipe works too.
I picked up all the supplies at my local Lowes.

Supplies needed:
-container
-length of .5 inch copper pipe
-Two .5" cooper pipe caps
-clear tubing (reinforced)
-rubber grommets (i found an assortment pack that had two .5 inch grommets)
-index card (for transferring cut line)

Equipment needed:
-Drill
-1" bit (I used a spade or "paddle" bit) This is based on the outside diameter of the grommets' inner ring...
-clamp (quick clamp or pipe clamp)
-hacksaw (or Dremel)
-coping saw
-crosscut saw (chop saw if you have it)
-safety stuff, glasses gloves and a mouthgaurd
-rounded file
-fine sand paper

Step 1: Measure and Cut

For my set up, I needed the knock box to fit in my espresso machine. Specifically, it had to fit in between the portafilter and the drip tray. This saves counter space and can also be used to catch drips. If you have a Gaggia Baby Class, then make your container 4" tall.

Step 2: Drill Holes

Practice making the holes on a scrap piece. Clamp the scrap to something to keep it from moving. I ended up having to slow the drill speed considerably at the end to avoid chipping out the back and having the wood ripped out of my hand. (hence mouthgard) A little chipping is okay and even a little burning is okay because the grommets will cover a bit of the hole edge. The hole will need to be slightly expanded to fit the grommet.
Measure 1 3/8 inch down from the top on both sides. If you plan on this fitting between the portafilter and the drip tray like mine, start doing some measuring for appropriate height so the bar will clear the spouts.
If you are feeling reckless, hold onto it with your hand. If not, clamp it down and drill baby drill.

Step 3: Cut Out "mouth"

Draw an arc for the mouth of the knock box on the cardstock.
4.25 inches across, 1.75 inches down.
Cut it out and trace it onto the wood.
I coped it out, but you could use a jigsaw.
It will be rough, but files and sandpaper make it look pro.

Step 4: File and Sand

Use a rounded file to expand the hole a bit. Keep checking the size by shoving the grommet in to check.
Make the "mouth" smooth.

Step 5: Insert Grommets

Pop in the grommets. I ended up using some pliers to pull them in.

Step 6:

Slide the pipe through to make sure it fits
Cut the pipe leaving enough for the end caps.
Debur the cut ends with files.

Step 7:

Cut the clear tubing to fit between the two grommets. Slide the pipe through, ad pop on the endcaps.
Mine pressure fit fine so no glue/soldder needed. You could slightly squeeze the copper pipe ends to make the end caps fit tightly.
After months of banging, no lose caps yet.