Bolt hole tolerances

Date 01-24-2019 16:46

My company has a machine that punches holes in thick angles such as 5/8'' - 1''. Upon mag particle inspection we are finding cracks that have got to be caused by the punching process. My question is, where can I find tolerances on bolt holes? I ve have been through AISC and RCSC and it is eluding me. Please help

By jwright650 (*****)

Date 01-24-2019 17:49

What size holes are you trying to punch? There are diameter vs thickness rules of thumb to follow as you can shatter the punch dies and it can be pretty dangerous when those hardened pieces go flying at a high rate of speed.

By SWN1158 (***)

Date 01-25-2019 15:22

Another thing is the hole diameter in the die. The hole diameter in the die is typically 1/32 larger than the punch for thinner material, and typically 1/16 larger for thicker material. Also, the die must be properly centered with the punch so that proper clearance is achieved.

By Steelslinger (**)

Date 01-24-2019 21:20

Try looking at the "RCSC Specifications for Structural Joints using High Strength Bolts" (also AISC Steel Construction Manual, 16.2) again, its in there. Try in Section 3.

Rule of thumb, you want the hole being punched to be at least 1/16" bigger than the thickness of the metal up to a point, then you want to be 1/8" bigger after that, unfortunately I don't remember what the thickness is.

Are the cracks radiating outward from the punched hole, or are they following the radius of the holes?

By thirdeye (***)

Date 01-28-2019 01:19

Sorry, I can't provide any help on tolerances, but I can share a little bolt humor.