One design consideration that comes up or is missing time and time again is the removal of the radius to internal corners left by our cutting tools so that a tight fit is achieved and the parts end up in the location required.
This radius is dependent on the size of the tool doing the cutting. This will either be determined by the type of material, the detail required or what is affordable.
The answer is the 'dog bone'. In our social media discussions with clients and other makers we've also heard these referred to as 'panda ears', 'bubbles' and other weird and wonderful lingo. There are a few options and each has their own pros and cons.
The type shown on the left is our most commonly used because if the part sliding in has a slot itself, these areas of extra removed material is hidden. If the material is 3/4" thick however a tool as small as 1/4" in diameter will need to be used for there to be material left in the middle for the part to collide with and lock into it's intended position. This size tool will increase cutting time and cost.
The type shown in the middle creates the smallest area of removed material left visible after a part slotted into this position. Again, for a 3/4" material a 3/8" diameter tool is the largest we could use and there would be an increase in machining time.
The type shown on the right is the most time/cost efficient method as it uses the same size tool as we'd typically use anyway. We use this type when seeing this detail is not important or it's in a location that isn't seen anyway.