Bearing Dimension Calculator

Bearing Dimension & Section Height Calculator

Calculated Specifications:

Section Height: 0 mm

Mean Diameter: 0 mm

Bore Code (ISO): N/A

Cross-Section Area: 0 mm²

Warning: Outer diameter must be larger than inner diameter.

function calculateBearing() { var d = parseFloat(document.getElementById("innerDiameter").value); var D = parseFloat(document.getElementById("outerDiameter").value); var B = parseFloat(document.getElementById("bearingWidth").value); var resDiv = document.getElementById("bearingResults"); var warning = document.getElementById("sizeWarning"); if (isNaN(d) || isNaN(D) || isNaN(B) || d <= 0 || D <= 0 || B <= 0) { alert("Please enter valid positive numbers for all dimensions."); return; } if (D = 20 && d < 500) { if (d % 5 === 0) { var codeVal = d / 5; boreCode = codeVal < 10 ? "0" + codeVal : codeVal.toString(); } else { boreCode = "/" + d; } } else if (d === 10) { boreCode = "00"; } else if (d === 12) { boreCode = "01"; } else if (d === 15) { boreCode = "02"; } else if (d === 17) { boreCode = "03"; } else if (d < 10) { boreCode = d.toString(); } else { boreCode = "/" + d; } document.getElementById("resSectionHeight").innerText = sectionHeight.toFixed(3); document.getElementById("resMeanDiameter").innerText = meanDiameter.toFixed(3); document.getElementById("resBoreCode").innerText = boreCode; document.getElementById("resCrossArea").innerText = crossArea.toFixed(2); resDiv.style.display = "block"; }

Understanding Bearing Dimensions (d x D x B)

In the world of mechanical engineering, identifying the correct bearing size is critical for machine longevity and performance. Most ball and roller bearings are identified by three primary dimensions: the Inner Diameter (d), the Outer Diameter (D), and the Width or Thickness (B).

The Basic Formula

The core geometry of a bearing can be summarized by these fundamental relationships:

• Section Height (H): The radial thickness of the bearing rings. Calculated as: (D - d) / 2.
• Mean Diameter (dm): The average of the bore and outside diameter, often used to calculate reference speeds. Calculated as: (D + d) / 2.
• Bore Code: For standard metric bearings, the last two digits of the bearing number usually indicate the bore size. For bores between 20mm and 480mm, multiplying the bore code by 5 gives you the inner diameter in millimeters.

How to Measure Your Bearing

If you don't have the part number, you can use a vernier caliper to find the dimensions:

1. Inner Diameter (d): Measure the internal hole of the inner ring.
2. Outer Diameter (D): Measure across the outside of the outer ring.
3. Width (B): Measure the thickness of the bearing from one face to the other.

Common Calculation Example

Suppose you have a bearing with the following measurements:

• Bore (d): 40 mm
• Outer Diameter (D): 80 mm
• Width (B): 18 mm

Using the formulas, the Section Height would be 20mm (80 – 40 / 2). The Bore Code would be "08" (40 / 5). This would typically correspond to a 6208 or 6308 series bearing depending on the specific diameter/width ratio.

Why Dimensions Matter

Choosing the wrong bearing dimensions leads to improper fitment, which causes excessive vibration, heat generation, and eventually catastrophic equipment failure. Always ensure your measurements are precise to within 0.01mm when selecting replacements for high-speed applications.