Mold Stop Posts (Ejector Plate Limit Posts), S45C — Pack of 4

Mold stop posts (limit posts) in S45C, sold in packs of 4 — the quantity a standard ejector plate uses. Sizes are given as outside diameter × height, with the mounting thread in brackets. All dimensions in millimetres.

What they do

Stop posts sit between the ejector plate and the clamping plate. They set where the ejector plate rests when it is fully back, and they take the impact each time it returns. They are counterbored for a socket head cap screw, so they bolt down rather than press in.

Two jobs come out of that. First, height: the post length is what actually determines your ejector home position, so it has to be right before the tool ever runs. Second, cleanliness — the posts hold the plate off the clamping face, so flash, swarf and broken pin fragments collect in the gap instead of under the plate. A plate resting directly on the clamping face will sit on the first chip that lands there and cock itself.

Why we sell them in fours

The four posts set the plane the ejector plate rests on. Replacing one worn post out of four leaves the plate tilted by exactly the amount that post has flattened — which is small, and which is why the resulting bent ejector pins and galled guide bushings usually get blamed on something else. If one has peened over enough to need replacing, the other three have taken the same number of returns.

If you are fitting a new tool, check all four heights against each other with a micrometer before assembly rather than trusting the tolerance.

Choosing a height

Measure with the ejector plate fully returned and the mold closed. The post height sets the gap; the gap has to leave the return pin faces flush with the parting line and the ejector pins flush with the cavity. Get the post too tall and the ejector pins stand proud into the cavity at rest — every shot marks. Too short and the return pins bottom before the plate does, so the posts carry no load and the return pins take the impact instead.

Thread and counterbore

Each size is listed with its mounting thread — M5, M6, M7 or M8 — because the same outside diameter is made with more than one thread. Ø15 comes in M5 and M6; Ø25 in M6, M7 and M8; Ø30 to Ø40 in M6 and M8. Check what is already in your plate before ordering, because the counterbore diameter and depth change with the thread and the screw has to sit below the post face.

If you are drilling new, the smaller thread in a given diameter leaves more material around the counterbore and is the safer choice unless you need the clamp load.

Specifications

A note on price and size

The price ladder here is not a smooth function of diameter and height, because we price from actual supplier cost rather than fitting it to a curve. Some mid-range sizes run cheaper than smaller ones simply because they are made in higher volume. The numbers are the real figures, not a mistake.

Larger and taller posts

Ø45 and Ø50 in taller sections, heights to 80 mm, and KO-post variants in M8 are all stocked — a set of four in those sizes runs to several kilograms and does not belong on a flat parcel rate. Request a quote for those and we will price the freight properly against your destination.

Shipping

International freight is calculated on packed chargeable weight. See Shipping & Delivery for destinations and transit times. Import duties and taxes are the buyer's responsibility — please read the duties section on that page before ordering.