Which hole type is recommended for through-bolting clearance to ease assembly?

• A. Tapped clearance holes
• B. Through-bolted clearance holes
• C. Blind clearance holes
• D. Through holes

Answer: (B)

When assembling parts with a through-bolt, the bolt must pass cleanly from one side to the other without being threaded into the hole. That means you need a clearance hole that goes completely through the material and is sized to allow the bolt shank to move freely. Using holes described as through-bolted clearance holes gives you exactly that: a hole through which the bolt can pass easily and be secured with a nut or a threaded insert on the opposite side. This setup reduces misalignment, speeds assembly, and avoids cross-threading because the threads are engaged elsewhere (in a nut or threaded boss), not in the hole itself.

Tapped clearance holes would imply threading the hole, which defeats the purpose of a pure clearance path for a through-bolt. Blind clearance holes don’t go all the way through, so they can’t accommodate a bolt passing completely through. Through holes by themselves don’t specify the clearance needed for the bolt, which is essential for easy assembly. Hence, the best fit is through-bolted clearance holes.