Technical Guide4 min read

How to Retrofit Free-Flange Stepped Pins in Existing Molds

Key Takeaway: Retrofit requires enlarging the ejector plate counterbore by 2–3mm to accept the free-flange collar. The cavity-side shaft and tip dimensions are identical — no cavity modifications needed.

Retrofit Procedure

Measure existing counterbore: Record the current counterbore diameter and depth.
Select free-flange pin: Match the shaft (D2) and tip (D3) diameters to the existing pin. The free-flange collar OD will be 2–3mm larger than the standard head.
Enlarge counterbore: Re-bore the ejector plate counterbore to accept the larger collar. Depth = collar thickness + 0.5mm clearance.
Install and set position: Follow the standard position setting procedure.

Cost-Benefit Analysis

Per-pin cost premium: 40–60% vs standard fixed-head. Counterbore enlargement: $10–15 per bore. The investment is justified when: (1) multiple pin lengths are tested during mold tryout, (2) the production run requires frequent stroke adjustment, or (3) you want to standardize spare pin inventory (one free-flange pin replaces multiple fixed-length pins).

Frequently Asked Questions

Will the retrofit affect part quality?+

No — the cavity-side geometry (shaft and tip) is identical to the original pin. The free-flange change only affects the plate side of the mold.

Can I retrofit one pin at a time?+

Yes — free-flange and standard fixed-head pins can coexist in the same ejector plate. Convert one at a time during maintenance as needed.