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.
-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)
-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)
-crosscut saw (chop saw if you have it)
-safety stuff, glasses gloves and a mouthgaurd
-fine sand paper
Step 1: Measure and Cut
Step 2: Drill Holes
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"
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
Make the "mouth" smooth.
Step 5: Insert Grommets
Cut the pipe leaving enough for the end caps.
Debur the cut ends with files.
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.