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How to Measure Pneumatic Cylinder Bore and Stroke
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Part number, brand, bore, stroke, series and cylinder type.
Bore and stroke are two of the most important pneumatic cylinder specifications, but they describe different parts of the cylinder.
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Bore: the internal diameter of the cylinder barrel.
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Stroke: the distance travelled by the piston and piston rod.
Check the label before measuring
Always begin with the manufacturer label or part number. Bore and stroke are frequently encoded within the model reference, and this is normally more reliable than estimating dimensions from the outside of the cylinder.
How to establish the stroke
Where the machine can be operated safely, the stroke can usually be established by measuring the piston rod movement between the fully retracted and fully extended positions.
Measure from the same fixed reference point in both positions. The difference between the two measurements is the stroke.
Do not use the cylinder’s overall extended length as the stroke measurement.
Can bore be measured externally?
Not accurately. The outside diameter or width of the cylinder body is not the same as the internal bore.
A 32mm bore profile cylinder, compact cylinder and roundline cylinder can all have very different external body dimensions.
How to identify the bore without dismantling the cylinder
Use the following information:
- Manufacturer part number
- Series designation
- Labelled bore size
- Manufacturer dimensional drawing
- Body dimensions compared with the correct series catalogue
Dismantling an unknown cylinder purely to measure the bore should normally be avoided unless the work is carried out safely by a competent person and the cylinder is already being removed from service.
Other dimensions required for replacement
Bore and stroke alone do not establish compatibility. Record:
- Retracted length
- Extended length where practical
- Mounting hole centres
- Front and rear mounting dimensions
- Piston rod diameter
- Piston rod thread
- Air port size and position
- Cylinder body width or diameter
- Sensor type and sensor groove arrangement
Before taking measurements
Isolate the compressed air supply, release stored pressure and secure any load or machine component that could move when the cylinder is disconnected.
Browse by bore size or stroke length.
