Pros
Cons
¼” Hex bits
Easier to find on the market.
Multiple suppliers provide ¼” Hex bits.
Depending on the supplier, the OD of the bit might differ between brands.
If OD of the bit is bigger that the OD of the screw, the bit has to be machined.
HM 4mm bits
Usually, OD of the bits are more consistent even between different suppliers.
It is less common to require additional bit machining to reduce the OD of the bit in comparison to ¼” Hex bits.
Better engagement between the tool and the bit than the ¼” Hex bit. (Usually the ¼” Hex bits wobble slightly)
Fewer options and suppliers provide this type of bits.
