Lag Bolts

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  • To suck in one member against an attachment surface, predrill the member the same size as lag bolt size. The surface is predrilled with a smaller hole. This way, the bolt slides in the hole in the member, sucking it in to the attachment surface.

Predrill Hole Size

From [1]:

  • For 1/2" bolts- 1/4". Softwood assumed.
  • 3/8" bolts - 11/64" predrill


  • Strengh is 450 lb per inch of thread in southern pine - [2]