From Flat Steel Blank to Rotating Component
Metal spinning takes a flat steel disc and forms it, under controlled roller pressure, over a rotating mandrel until it takes the profile of the finished pulley. JBMK runs this process on CNC-controlled multi-roller spinning and flow-forming machines with automatic playback profiling — the same tooling category used for our crankshaft and damper components — giving repeatable wall thickness and roundness across high production volumes.
Because the material is worked rather than cast or fully machined from bar stock, spun pulleys typically run 30–40% lighter than an equivalent cast-iron part, with no loss of torsional strength at the groove section. That weight reduction is the same "casting-to-sheet-metal conversion" engineering JBMK has supplied to global automotive OEMs for over a decade.
CNC Flow Forming
Cold rolling of grooves directly into the spun shell for up to 40% mass reduction versus cast.
In-House Mandrel Tooling
Spinning mandrels designed and machined in our own toolroom, cutting lead time on new part introduction.
9 Spinning & Flow-Forming Machines
Dedicated CNC playback spinning capacity separate from our stamping and machining lines.
Dynamic Balancing Verified
Every spun pulley family checked to G2.5 (ISO 1940) balance grade before release.