When designing for compactness, tightening bolt holes with partially missing counterbore sections can often be seen, with the following problems.

Problem of missing counterbore sections

• Partially remaining material may cause injuries to fingers, etc.
• May cause malfunctions of sliding mechanisms due to the notched portion falling off.

Countermeasures

(1) At the time of designing, evaluate the external dimensions and the hole locations to avoid the "notches" (See [Fig.2], [Fig.3])

(2) Machine off the sections that become narrow during the manufacturing process (See [Fig.4])