Engineering · Reference
O-ring groove design chart.
Groove dimensions for the five AS568 standard O-ring cross-sections in industrial static glands, per the Parker O-Ring Handbook ORD-5700. Gland depth, groove width, squeeze, clearance, and groove radius for radial (piston/bore) seals, a second table for face (axial) seals, and the design rules that make a static seal work: ~75% gland fill, ≤5% stretch, lead-in chamfers, and clean sealing surfaces.
01 · Gland anatomy
Depth sets the squeeze. Width sets the fill.
A static O-ring seal works by squeeze: the rectangular groove (gland) is shallower than the O-ring cross-section, so closing the assembly compresses the rubber between the groove floor and the mating surface. Gland depth L — groove floor to the mating wall, including the clearance gap — is what actually sets the squeeze, so the machined groove depth is L minus half the diametral clearance. Groove width G is cut wider than the cross-section so the displaced rubber has somewhere to go — the ring should fill about 75% of the groove volume, never 100%.
Radial glands seal across a diameter — a groove in a piston (male) or bore (female), squeezed between piston and cylinder wall. Face glands seal axially between two flat faces, like a cover plate on a housing, and take a heavier squeeze. The two geometries use different dimensions — don't mix the tables. Mating diameters around a radial gland are toleranced like any precision bore and shaft; see standard fits for the fit classes and surface finishes for what the RMS callouts mean on the print.
Radial gland dimensions — piston or bore groove, AS568 cross-sections
Industrial static radial seals — a groove in a piston (male gland) or bore (female gland) with squeeze acting diametrally. Groove width G is the no-back-up-ring width, good to 103.5 bar (1500 psi); above that, add one or two back-up rings and widen the groove per ORD-5700 widths G1/G2. All dimensions in inches.
| AS568 series | Cross-section W (in) | Gland depth L (in) | Squeeze (in) | Squeeze (%) | Groove width G (in) | Diametral clearance E (in) | Groove radius R (in) | Max ecc. TIR (in) |
|---|---|---|---|---|---|---|---|---|
| -0xx -004 … -050 | 0.070 1/16″ nom · ±0.003 | 0.050–0.052 | 0.015–0.023 | 22–32% | 0.093–0.098 | 0.002–0.005 | 0.005–0.015 | 0.002 |
| -1xx -102 … -178 | 0.103 3/32″ nom · ±0.003 | 0.081–0.083 | 0.017–0.025 | 17–24% | 0.140–0.145 | 0.002–0.005 | 0.005–0.015 | 0.002 |
| -2xx -201 … -284 | 0.139 1/8″ nom · ±0.004 | 0.111–0.113 | 0.022–0.032 | 16–23% | 0.187–0.192 | 0.003–0.006 | 0.010–0.025 | 0.003 |
| -3xx -309 … -395 | 0.210 3/16″ nom · ±0.005 | 0.170–0.173 | 0.032–0.045 | 15–21% | 0.281–0.286 | 0.003–0.006 | 0.020–0.035 | 0.004 |
| -4xx -425 … -475 | 0.275 1/4″ nom · ±0.006 | 0.226–0.229 | 0.040–0.055 | 15–20% | 0.375–0.380 | 0.004–0.007 | 0.020–0.035 | 0.005 |
Per the Parker O-Ring Handbook design chart “For Industrial O-Ring Static Seal Glands” (Design Chart 4-1 in ORD 5700A; renumbered 4-2 in the current ORD-5700 e-handbook — same values). Gland depth L is measured groove floor to mating wall and includes the clearance gap, so the machined groove depth is L − E/2. Clearance E is the extrusion gap — hold it to the minimum the design allows, and cut the listed maximum clearance in half for silicone or fluorosilicone compounds. Eccentricity is total indicator reading between the groove and the adjacent bearing surface. Surface finish (RMS): 32 µin on the groove floor and mating sealing wall, 63 µin on the groove sidewalls — free of scratches, pits, and spiral tool lay across the seal path. Groove sidewalls may taper 0–5°; break corners ~0.005″ R.
Face seal gland dimensions — axial squeeze between flat surfaces
Face (axial) seals take a heavier squeeze than radial glands and use a narrower groove for vacuum and gas service, which raises gland fill and contact stress for a tighter seal. Locate the groove from the pressure side: internal pressure → dimension the groove OD = mean O-ring OD; external pressure (or vacuum) → groove ID = mean O-ring ID, so pressure pushes the ring against the supported wall. All dimensions in inches.
| AS568 series | Cross-section W (in) | Gland depth L (in) | Squeeze (in) | Squeeze (%) | Groove width G — liquids (in) | Groove width G — vacuum & gases (in) | Groove radius R (in) |
|---|---|---|---|---|---|---|---|
| -0xx -004 … -050 | 0.070 1/16″ nom · ±0.003 | 0.050–0.054 | 0.013–0.023 | 19–32% | 0.101–0.107 | 0.084–0.089 | 0.005–0.015 |
| -1xx -102 … -178 | 0.103 3/32″ nom · ±0.003 | 0.074–0.080 | 0.020–0.032 | 20–30% | 0.136–0.142 | 0.120–0.125 | 0.005–0.015 |
| -2xx -201 … -284 | 0.139 1/8″ nom · ±0.004 | 0.101–0.107 | 0.028–0.042 | 20–30% | 0.177–0.187 | 0.158–0.164 | 0.010–0.025 |
| -3xx -309 … -395 | 0.210 3/16″ nom · ±0.005 | 0.152–0.162 | 0.043–0.063 | 21–30% | 0.270–0.290 | 0.239–0.244 | 0.020–0.035 |
| -4xx -425 … -475 | 0.275 1/4″ nom · ±0.006 | 0.201–0.211 | 0.058–0.080 | 21–29% | 0.342–0.362 | 0.309–0.314 | 0.020–0.035 |
Per the Parker O-Ring Handbook design chart “For O-Ring Face Seal Glands” (Design Chart 4-2 in ORD 5700A; renumbered 4-3 in the current ORD-5700 e-handbook — same values). Surface finish (RMS) on the sealing faces: 32 µin for liquids, 16 µin for vacuum and gases; groove sidewalls 63 µin. Groove sidewalls may taper 0–5°; break corners ~0.005″ R.
02 · Design rules
The rules that keep a static seal sealing.
The chart gives the numbers; these are the constraints behind them, straight from ORD-5700. Break any one of them and the gland can leak even with a perfect groove.
- Gland fill ~75% — never 100%: the O-ring should occupy 60–85% of the groove volume, optimum 75%, and always at least 10% void. Rubber is incompressible — it deforms, it doesn't compress — so a full groove plus thermal expansion or fluid swell will burst the joint open or extrude the ring.
- Installed stretch ≤ 5%: I.D. stretch in the groove should not exceed 5% — more thins the cross-section, cuts the effective squeeze, and shortens seal life. Momentary stretch during assembly should stay under 50% of the compound's ultimate elongation, with time to recover before closing the gland.
- Lead-in chamfer, 10–20°: every edge the O-ring slides over during assembly gets a smooth, burr-free 10–20° lead-in chamfer. Never push a ring over unprotected sharp corners, threads, keyways, splines, or cross-drilled ports — chamfer or undercut ports the seal must pass.
- No parting line or defect on the sealing surface: keep mold parting lines, flash witness, scratches, pits, porosity, and spiral tool lay off the groove floor and the mating sealing wall. A leak path only needs to be a few ten-thousandths deep. Finish callouts are RMS — see the surface finish reference for conversions.
- Control the extrusion gap: diametral clearance E is where the ring extrudes under pressure. Hold it to the minimum the assembly allows, halve the listed maximum for silicone and fluorosilicone, and add back-up rings (with the wider G1/G2 grooves) above 1500 psi.
- Don't pinch at closure: close the gland with straight axial motion — no rotation — and make sure the groove corners can't trap the ring as the parts come together. Concentricity matters too: hold the eccentricity (TIR) limits in the radial table.
03 · Machining the gland
We cut the groove; you call the compound.
O-ring glands are bread-and-butter machining: single-point turned grooves on pistons, bores, and glands; milled face-seal grooves on covers and manifolds; held to the depth, width, finish, and concentricity limits in these tables. The details that matter at the spindle are the ones the chart calls out — groove-floor finish without spiral lay, square sidewalls within the 0–5° allowance, broken corners, deburred lead-ins, and gland depth measured and certified rather than assumed from the groove cut.
The elastomer itself — compound, durometer, and size — is specified by your design or your seal supplier; we machine the gland to your print and the seal drops in at assembly. If the drawing calls a gland that fights these tables (wrong fill, no lead-in, finish the groove can't live with), we'll flag it at quote rather than after first article.
Keep exploring
Related tools & references
What 16/32/63 RMS mean and how to call them out on the gland print.
Fit classes for the piston and bore diameters around a radial gland.
Through-hole sizing for the fasteners that clamp a face-seal joint.
Printable limits-and-fits reference for toleranced gland diameters.
Technically reviewed by the True Precision Machining engineering team · Last reviewed June 2026
Standards referenced: AS568, Parker ORD-5700
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