The part itself is the best drawing you have
If you can post us the old component, do that first and read the rest of this afterwards. A physical sample removes almost all the ambiguity: we can measure it properly, assess the compound and check the bond construction. Send the worn one even if it is damaged — a broken part still carries most of its dimensions.
If it cannot leave the site because the machine is running on it, the next section is what we need instead.
What to measure
- 1Overall dimensions. Outside diameter, inside diameter, thickness or height. Use vernier callipers, not a steel rule — 0.5 mm matters on a seal.
- 2Section shape. Photograph the cross-section against a scale. If the part is symmetrical, cut a spare in half; the section tells us more than any single dimension.
- 3Metal inserts. Where the part is bonded to metal, record the insert dimensions, thread size and material separately. These usually matter more than the rubber.
- 4Hardness, if you can. A Shore A durometer costs little and removes the biggest guess. If you do not have one, say how it feels — like a tyre tread (around 65), a pencil eraser (around 50), or a hard nylon washer (85 plus).
- 5Free versus fitted state. Rubber relaxes once removed. If the part was compressed in service, tell us — the moulded dimension is not the fitted dimension.
Measure a new one if there is any chance
A worn part has lost material and may have taken a compression set. If there is an unused spare anywhere on site, measure that instead and tell us which one you measured.
What to tell us about the duty
Dimensions get the shape right. The duty gets the compound right, and the compound is what determines whether the new part lasts longer than the old one.
- What fluid or media does it touch? Oil, water, steam, a named chemical, food product, or nothing but air.
- What temperature does it see? Both the normal running temperature and any peak — a CIP wash cycle or a nearby heat source often sets the real limit.
- Is it static or moving? A gasket that is clamped and never moves is a completely different design problem from a seal on a reciprocating rod.
- What pressure, if any?
- How did the old one fail? Hardened and cracked, swollen and soft, torn, worn thin, or debonded from its metal. Each failure mode points at a different fix.
That last question is the most valuable one on the list and the one most often left unanswered. A part that hardened and cracked was too hot or wrongly compounded for ozone. A part that swelled soft was chemically wrong. A part that wore thin was too soft or the wrong polymer for abrasion. The failure tells us what to change.
What happens next
- 1We come back with questions if anything is ambiguous, and with a proposed compound and hardness.
- 2You get a written quotation covering the part price, any tooling cost, and the minimum quantity.
- 3A die is cut in our own tool room — days rather than the three or four weeks an outsourced tool room needs.
- 4A first sample comes to you for physical approval before any production quantity is released.
- 5Once approved, the tooling stays with us, so repeat orders skip all of the above.
On tooling cost
Compression moulding tooling is far cheaper than injection tooling, which is precisely why it suits low volumes. For many simple parts the die cost is recovered on the first order. Ask us to quote tooling separately so you can see it.
A short checklist
Photograph the part next to a ruler from three angles. Record OD, ID, thickness and any insert dimensions. Note the fluid, the temperature and how the old part failed. Send it all in one message. That is genuinely enough to start.
Have a part that fits this description?
Send the dimensions and the operating conditions. We will tell you what compound it should be in and quote it — including saying so if it is not a job for us.