For mounting bracket using M6x1.0 fasteners in aluminum with loose tolerances, what clearance hole size would you specify?

• A. 6.60 mm (G)
• B. 6.30 mm (E)
• C. 6.00 mm (F)
• D. 6.90 mm (H)

Answer: (A)

Clearance holes are sized to be larger than the bolt’s major diameter so the bolt can pass through without threading into the hole, even when parts vary due to tolerances. For an M6 bolt, the nominal diameter is about 6.0 mm, but tolerance stacks in aluminum with loose tolerances can push the actual size up to a few tenths of a millimeter. Giving the hole extra clearance helps ensure smooth assembly despite burrs, misalignment, or part variation.

Choosing a hole around 6.60 mm provides about 0.60 mm of clearance, which is enough to accommodate typical variation while maintaining reasonable clamping and alignment. The other options either risk interference (6.00 or 6.30) or introduce too much play (6.90). So, 6.60 mm is the best fit for this scenario.