Margo Rubber Products
Rubber plunger seals and plunger cups
SHORE A
±5 pts — quoted with the diameter tolerance, not separately
TENSILE
Per compound datasheet, tested to ASTM D412

Reciprocating Seals

Plunger Seals & Plunger Cups — Moulded for the Fluid You Pump

Moulded plunger seals and plunger cups for reciprocating pumps and sprayers, bonded to your stem where the design calls for it. The plunger sits inside the fluid on every stroke — so we choose the compound from what you are pumping, not from a default, and quote the diameter tolerance against the bore it runs in.

HARDNESS
70 Shore A typical, 60–90 available
TEMPERATURE
Set by the compound and the fluid pumped
PLUNGER DIAMETER
To your drawing
BORE DIAMETER
The bore the plunger runs in
STROKE
Length and strokes per minute
FLUID PUMPED
The specification that comes before every other one
CONSTRUCTION
All-rubber, or bonded to a metal stem
QTY (pieces)
−10,000+
Minimum run: 10,000 pieces per part number
Request QuoteRequest documentation
  • MADE TO ORDER
  • ISO 9001:2015
  • 09111526A

Product gallery

Visual Reference

360° PREVIEW

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Cross section viewSection through the plunger and its bore — on request under NDA

Plunger diameter
With tolerance
Bore diameter and finish
Diameter, material and surface finish
Sealing length
The band that contacts the bore
Stem interface
Bonded, threaded or clamped
Working pressure
And whether the stroke is pressure or suction

Section drawing available on request. Send the bore diameter, the plunger diameter, the stroke and the fluid — or a sample and the pump make — and we will return a dimensioned drawing with the compound recommended for that fluid.

Technical specifications

Engineering Data

Product Family
Reciprocating Seals
Material
Selected from the fluid pumped
Hardness (Shore A)
70 Shore A typical, 60–90 available
Tensile Strength
Per compound datasheet, ASTM D412
Elongation at Break
Per compound datasheet, ASTM D412
Operating Temperature
Set by the compound and the fluid
Compression Set
ASTM D395 Method B
Density
Per compound datasheet
Colour Options
Black standard, custom RAL on request
Lead Time
Confirmed with the quotation, from approved drawing and approved sample
Fluid compatibility
Confirmed against the fluid before the compound is fixed
Abrasion resistance
DIN 53516 / ISO 4649 — on request, tested externally
Plunger diameter tolerance
Quoted against your bore, not in isolation
Construction
All-rubber, or bonded to a metal stem
Rubber-to-metal bond
In-house, chemical bond to a prepared metal surface
Working pressure
To your specification
Certifications
ISO 9001:2015 — certificate 09111526A, valid to 21 February 2027
Minimum Order
10,000 pieces per part number, per compound, or quoted against the part where geometry or tooling makes that unrealistic. Prototype and first-article lots sit outside the minimum.

Dimensional reference

To customer drawing
Plunger diameter
With tolerance
Bore diameter and finish
Diameter, material and surface finish
Sealing length
The band that contacts the bore
Stem interface
Bonded, threaded or clamped
Working pressure
And whether the stroke is pressure or suction

Available materials

Rubber Compound Options

Select the compound best suited to your operating environment and application requirements.

Tell us what the pump moves — pick the compound for that fluid.

Not sure? Send the medium, temperature and load

Rubber plunger seals and plunger cups

COMPOUND FROM THE FLUID

Not pre-selected

the plunger sits in it

Key advantages

Why Specifiers Choose Margo

  • The plunger lives inside the fluid

    Not near it — in it, on every stroke, for the life of the pump. Get the elastomer wrong and it swells until it jams in the bore. We fix the compound from what you pump, before anything else is decided.

  • The bore is half the specification

    A plunger seals by interference against something. Send the bore diameter, its material and its surface finish — a correct plunger in a scored bore fails in weeks, and the plunger gets the blame.

  • Bonded to your stem, in-house

    Most plungers are a rubber element on a metal rod. We prepare the metal and chemically bond the rubber to it in our own plant, so the joint is not a second supplier’s problem.

  • It moves, so it wears

    Compression set describes a static seal. On a reciprocating plunger, abrasion resistance and friction decide service life — we specify for the stroke rate you give us, and arrange abrasion testing where the duty warrants it.

Industries served

Global Applications

  • Agricultural sprayers

    knapsack and power sprayer pumps, where the plunger runs in a chemical solution all season

  • Dosing and water treatment

    metering pumps handling dilute acids and alkalis, the duty EPDM is genuinely right for

  • Automotive and workshop equipment

    hand and hydraulic pumps, greasing equipment, oil dispensers

  • General industrial pumps

    reciprocating and diaphragm pumps across process plant, on oils, fuels and hydraulic fluid

Manufacturing process

From Compound to Certification

  1. Material compounding

    Polymer blending, additive integration and batch QC in our in-house lab. The compound is chosen from the fluid the pump moves, since the plunger is submerged in it on every stroke.

  2. Mould Design & CNC

    Mould design and manufacture in-house, held as a controlled record. Plunger cavities are cut to the diameter tolerance quoted against your bore.

  3. Metal preparation and bonding agent application, where the plunger is bonded to a stem. Degrease, abrade, prime

    The bond is made during cure, not afterwards.

  4. Post-Cure & Trimming

    Compression moulding, cure and deflash. The sealing band is the critical surface and is finished accordingly.

  5. Quality inspection

    Plunger diameter and sealing length against the drawing, hardness to the specified tolerance, and bond integrity checked on bonded parts.

  6. Export packaging

    Industrial packing with documentation. Plungers are packed so the sealing band is not deformed in transit, since a flat spot on that band is a leak on arrival. ISPM-15 treated pallets where timber packaging is used.

Quality assurance

Certified to International Standards

Every product leaves our facility with a documentation package — material test reports, dimensional inspection sheets and a certificate of conformance — giving traceability from raw material to finished part.

  • ISO 9001:2015 · Certificate 09111526A

    Integral Certification Ltd · Valid to 21 February 2027

    Scope: rubber moulded components — quality management, not a product approval

  • IATF 16949 — upgrade in progress, certification targeted by end 2026

  • ISO 14001 and ISO 45001 — targeted 2027

No potable-water, food-contact or pharmaceutical approval is held.

Certification detail

Production metrics

Since 2005
In operation
60+
Active clients
3–4 weeks from approved sample
Avg. lead time

Downloads

Technical Documentation

Compound compatibility data and sealing profiles are issued on request, under NDA where required. Tell us what the pump moves, the bore diameter and the stroke, and we will recommend a compound and return a dimensioned drawing.

Request compatibility data

FAQ

Technical & Commercial Questions

Answers to the most common questions from engineering teams and procurement managers worldwide.

  • What is the minimum order quantity for this part?

    We supply in bulk. The minimum run is 10,000 pieces per part number, per compound. A plunger in two compounds is two part numbers — and on this part that is common, since the same pump body is sold for water and for oil. Prototype and first-article lots sit outside the minimum.

  • Can you match a competitor specification or reverse-engineer an existing part?

    Yes — send the plunger and tell us what the pump moves. A swollen plunger measures larger than it was made, and a worn one measures smaller, so a used sample copied dimensionally reproduces the failure rather than the part. The fluid tells us what happened to it.

  • What file formats do you accept for drawings?

    PDF, DWG, DXF and STEP. A plunger drawing needs the bore it runs in — diameter, material and surface finish — along with the stroke, the strokes per minute and the fluid. Without the bore, the diameter tolerance cannot be set.

  • Do you provide material test reports with each shipment?

    Yes. Material test reports, dimensional inspection sheets and a certificate of conformance ship with every consignment. Hardness and tensile to ASTM D412 and compression set to ASTM D395 Method B, tested in-house. Abrasion testing to DIN 53516 is arranged externally where the duty warrants it.

  • What are your payment and delivery terms for international orders?

    TT and LC accepted, discussed per order. Ex-works Nashik or FOB Nhava Sheva. Commercial invoice, packing list and certificate of origin are issued with every consignment. Plungers ship so the sealing band is not deformed in transit.

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Need this part quoted?

Tell us what the pump moves, the bore diameter, the plunger diameter and the stroke — a drawing if you have one, the pump make and a sample if you do not. We confirm the compound against the fluid before quoting anything, then price against your annual quantity. We respond within 48 hours.

Request a quoteBack to Reciprocating Seals