O-Ring Groove Size Calculator
Groove width and depth for an FKM (Viton) O-ring in an axial reciprocating seal.
Inputs
Applies to FKM O-rings in axial reciprocating seals only.
Results
Unrounded values
How this calculator works
PDCPD molds and RIM equipment use O-rings on moving parts such as core pulls, ejector systems and hydraulic cylinders. For an axial reciprocating seal the groove must leave enough squeeze to seal but enough room for the ring to move without rolling.
This calculator gives the groove width and depth for a fluoroelastomer (FKM) O-ring from its cross-section diameter.
Formulas
- Groove width
cross-section − 0.15- Groove depth
cross-section − 0.5
Results are shown to 1 decimal place. Open the formulas section for unrounded values.
Worked example
A 4 mm cross-section FKM O-ring:
| O-ring cross-section diameter | 4 mm |
|---|
| Groove width | 3.9 mm |
|---|---|
| Groove depth | 3.5 mm |
When to use it
- Designing seal grooves on hydraulic core pulls and slides
- Replacing O-rings and checking existing groove sizes
Frequently asked questions
What groove size do I need for a 4 mm O-ring?
For a 4 mm FKM O-ring in an axial reciprocating seal, the groove width is 3.85 mm (shown as 3.9) and the groove depth is 3.5 mm.
What is the formula for O-ring groove width and depth?
Groove width = cross-section − 0.15 mm. Groove depth = cross-section − 0.5 mm.
Does this apply to static seals or other rubbers?
No. The rule is for FKM O-rings in axial reciprocating motion. Static seals and other elastomers need different squeeze values.
Related calculators
Results are estimates from empirical rules used in PDCPD mold development. Verify critical dimensions before cutting metal.