Fastener Torque Capacity
Fastener Torque Capacity
(OP)
Does anyone know where I can find a chart that shows fastener toqueing capacity based on the type of head (i.e. SHCS, Flat, button, Hex, etc.)?
Any help would be appreciated.
Pat
Any help would be appreciated.
Pat





RE: Fastener Torque Capacity
RE: Fastener Torque Capacity
What does the type of head have to do with fastener torque?
JHG
RE: Fastener Torque Capacity
I'm guessing not all head types are made in all grades. For example maybe you cannot find a Grade 8 button head capscrew, so in that sense you can find a difference.
RE: Fastener Torque Capacity
RE: Fastener Torque Capacity
RE: Fastener Torque Capacity
RE: Fastener Torque Capacity
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Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Fastener Torque Capacity
The socket head cap screw design is an exception and it is structural, even under a wedge loading. The common pan head design is semi marginal. In almost all cases it will carry a full thread UTS in both straight and wedge tensile, but there are drive types and fastener sizes where it will not be sound under a wedge loading.
We had a long time engineer in our office who used to say that you can have a low head or a strong head, but not both.
One place to see this effect is in ISO 898-1, where they state in the scope of the spec that "Certain fasteners may not fulfill the tensile or torsional requirements of this part of ISO 898 because of the geometry of the head which reduces the shear area in the head as compared to the stress area in the thread such as countersunk, reased countersunk and cheese heads (see clause 6)."
RE: Fastener Torque Capacity
I have had problems in the past torquing 4-40UNC stainless steel hex socket flat head screws. I did not solve the problem by specifying the correct torque. I solved it by specifying phillips flat head machine screws (and changing the countersinks).
I do not think you should let the socket or other fastener engagement dictate the clamping force of your screw.
JHG