Family molds — tools that mold different parts in different cavities — have a persistent problem: you cannot always fill every cavity on every run. When a customer drops a part or changes a quantity, you need to stop flow to a cavity without cutting steel. That is exactly what runner shut-offs are for.
Tooling Components carries runner shut-off inserts from DMS Components in three sizes — RSO-13, RSO-16, and RSO-26 — sized by the runner diameter they fit (13, 16, and 26 mm respectively). The inserts block or open the runner path reversibly, so cavity selection becomes a setup decision instead of a rework job.
Machining the pocket
The DMS catalog gives precise pocket dimensions for each size. The RSO-13 fits a 13 mm runner with a 0.5118-inch body diameter; the RSO-16 fits a 16 mm runner at 0.6299 inches; the RSO-26 fits a 26 mm runner at 1.0236 inches. Each pocket requires a minimum plate thickness — 0.875 inches for the RSO-13 and RSO-16, and 1.375 inches minimum for the RSO-26.
Two details in the machining instructions are easy to miss. First, the spring-pin hole must be located away from the area where the runners are to be machined — the spring pin holds the insert in position while you cut the runner, and a 0.035-inch minimum land must remain between the edge of the runner and the edge of the spring-pin hole. Second, sharp carbide cutters are recommended for machining the runners.
Sizing the runner
The catalog also provides recommended runner sizes for each insert — width, depth, radius, and cross-sectional area — so the runner you machine into the insert carries the material volume the cavity needs. The recommended runner sizes are tabulated per insert: the RSO-13 handles runners around 0.099 to 0.126 inches wide, the RSO-16 extends to about 0.206 inches, and the RSO-26 takes runners up to roughly 0.446 inches wide.
Match the runner cross-section to the cavity's fill requirement — an undersized runner starves the cavity and packs it late; an oversized one adds cycle time and regrind.
The flexibility payoff
With runner shut-offs installed, you can run a family mold in different configurations without touching the tool steel: close one cavity for a partial run, open it again next month, and keep the balance predictable every time. That is real flexibility for a shop running mixed-volume production.
Tooling Components stocks RSO-13, RSO-16, and RSO-26 runner shut-offs and can help you spec pocket dimensions and runner sizes for your mold plates.
Contact Tooling Components at (800) 992-4766 for runner shut-off selection and pocket machining guidance.