1. Structural Differences & Standards (DIN 7979 vs DIN 6325)
Plain dowel pins (DIN 6325 / ISO 8734) are solid, precision-ground cylinders with chamfered ends. Tapped dowel pins (DIN 7979 / ISO 8735) incorporate a concentric female metric thread at one end and an axial air release flat along the shank body.
2. Extraction Mechanics in Blind Holes
In blind mold plate holes, plain dowels become permanently trapped unless knock-out pin holes are drilled from the reverse side. Tapped dowels solve this: maintenance technicians thread a extractor screw into the pin tip and effortlessly extract it with a puller tool during mold teardown.
3. Air Release & Pneumatic Pressure Prevention
Press-fitting a plain dowel into a blind hole compresses air at the bottom, creating back-pressure that prevents complete pin seating. Tapped dowels feature an integrated vent flat (air relief ground flat) that lets air escape freely during installation.
4. Shear Load Capacity & Fit Precision
Both types are manufactured from hardened alloy steel (SUJ2 / 100Cr6 or H13) hardened to 58–62 HRC with m6 or h6 diameter tolerances. For extreme heavy-die shear alignment where maximum solid cross-section is required, plain dowels are preferred.
5. Selection Guide for Tooling Engineers
Use Tapped Dowel Pins for blind cavities, core insert retainers, and plates requiring frequent maintenance. Use Plain Dowel Pins for through-bolted guide plate alignment where reverse ejection is accessible.