T-type angle pin seats, made to your drawing. The seat is the machined pocket-and-shoulder component the angle pin's root sits into. This page is about the bending moment at the root — the thing that decides whether a pin has a long life or shears at the head. For pin clamping see the DY angle pin fixing block; for the shouldered load path see the T-type angle pin fixing block.

Why pins break at the root, and what the seat has to do about it

An angle pin is a cantilever. The slide load acts out along the pin, the pin is held at its root, and the bending moment is highest exactly where the pin meets its seat. That is why sheared angle pins almost always fail at the head or just under it, not out in the free length.

Two seat features control that stress:

• Support depth. The deeper the pin is supported at the root, the more the load is spread and the lower the peak stress. A shallow seat concentrates everything into a narrow band.
• The transition at the mouth of the seat. A sharp corner where the pin exits the seat is a stress raiser, and it is where the crack starts. A radius or a small relief at the mouth spreads the transition. If your drawing does not call one out, say so and we will propose one rather than machining a sharp corner by default.

Squareness and seating contact

The pin has to bear over its whole seated surface, not on one edge. A seat that is a degree out of true, or that has a burr or a raised witness at the bottom of the pocket, tips the pin and turns full-face bearing into line contact — and the pin then bends around that line. On a mold showing repeated angle-pin failures, this is worth checking before the pin material is blamed.

Tell us the flatness and squareness you need on the seating faces; if you do not, we work to normal practice and write the assumption on the quotation so you can correct it.

What to send us

• Seat overall length, width and height
• Pocket dimensions, support depth, and the mouth radius or relief you want
• Bore or seat angle, and the pin diameter it receives
• Mounting-hole, thread and counterbore layout, and centre distances
• How the seat locates in the plate — shouldered into a pocket, dowelled, or bolted to a face
• Flatness and squareness requirements on the seating faces
• Material, heat treatment, hardness, tolerance, quantity and destination

Replacing a seat on a mold that has been shearing pins? Send a photo of the fracture face if you still have the broken pin. Where it broke, and whether the fracture is clean or beach-marked, tells us whether you have an overload problem or a fatigue problem — and those need different fixes.

Documentation and confidentiality

Material certificates, hardness results and dimensional inspection reports are available, with scope and cost confirmed in the quotation. Technical files are used to evaluate and fulfill your inquiry or order. They may be shared only with relevant manufacturing, inspection, logistics or service partners as needed. Send only files you are authorized to share. See our Privacy Policy. NDA on request from rfq@privleymold.com.