Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
ASME B5.5-1959 — Rotating Air Cylinders and Adapters
⚙️ ASME B5.5-1959 is a historic American National Standard that defines rotating air cylinders and adapters used on machine tool spindles. The standard evolved from B5.5-1932, developed by Technical Committee No. 11 on Chucks and Chuck Jaws of Sectional Committee B5. It was reaffirmed without change in 1949, editorially revised in 1954 to align its footnotes with the Unified and American Screw Thread standards, and finally approved by the American Standards Association (ASA) on November 11, 1959 under the designation “Rotating Air Cylinders and Adapters.” It belongs to the series of standards for Small Tools and Machine Tool Elements and provides a common mounting interface for air-operated and hydraulically actuated chucks on machine spindles.
💡 Core objective of the Standard: cylinders made by different manufacturers must be interchangeable on machine tool spindles without changing the adapter or the draw rod. This interface-standardization philosophy is the same one that drives today’s modular tooling interfaces.
1. Background and Scope 📌
A rotating air cylinder is a power element mounted behind the spindle of a lathe or grinding machine. Through a draw rod, it transmits axial force to a power chuck at the spindle nose to clamp and release the workpiece automatically. Before B5.5 was issued, manufacturers’ cylinders differed in mounting interfaces, piston rod dimensions, and draw rod threads, forcing users to rework components every time a cylinder or chuck was changed.
The scope of the Standard can be summarized as follows:
- Standard cylinders: a series of pneumatic rotating cylinders with bore sizes from 3 inches (about 76 mm) through 18 inches (about 457 mm), plus a 20-inch (about 508 mm) bore option.
- Standard adapters: four sizes, A, B, C, and D, matched to cylinder bore ranges, used to mount the cylinder on different machine spindles.
- Draw rod and piston rod interfaces: stroke length, piston rod position at the end of stroke, piston rod diameter, and the tapped hole in the piston rod are all standardized so that draw rods do not have to be individually fitted.
⚠️ B5.5-1959 is a historical edition. For current engineering use, consult the latest ASME edition or the applicable replacement standard. This article is compiled from a scanned copy for reference to the historical dimensions and interface logic.
2. Standard Adapter Classes and Interchangeability 🔧
The Standard defines four adapter sizes designed to let a cylinder be mounted on various machine spindles:
| Adapter | Cylinder Bores Served | Approx. Outside Diameter | Typical Applications |
|---|---|---|---|
| Adapter A | 3-in and 4½-in cylinders | About 5⅝ in | Small lathes, tool-room spindles |
| Adapter B | 6-in and 8-in cylinders | About 8¾ in | Small and medium lathes, cylindrical grinders |
| Adapter C | 10-in through 18-in cylinders | About 8⅜ in (with extra hole circle) | Medium and large lathes, heavy spindles |
| Adapter D | 20-in cylinder or power devices with 26,000–40,000 lb draw rod pull | About 8⅜ in | Very heavy draw-rod power devices |
Standard adapters have hubs large enough to cover the majority of cases: the user can bore and thread the standard adapter to fit the machine on which the cylinder will be installed. If the dimensions are not satisfactory, special adapters may be ordered or the user may make an adapter to fit the standard cylinder.
✅ Key interchangeability detail: with the piston at one end of its stroke, the piston rod projects 1 inch beyond the hub face; at the other end it projects 1 inch plus the stroke length. This convention makes draw rod length calculations simple and direct.
3. Cylinder Sizes and Pull Data 📏
The Standard standardizes a series of cylinder bores for which the stroke length, piston rod position at stroke end, piston rod diameter, and tapped hole size in the piston rod are all fixed. Piston rod diameters are kept as small as consistent with the required strength so that cylinders can be used on spindles with comparatively small holes. Pull data at 100 psi (about 0.69 MPa) supply pressure are summarized below:
| Bore (in) | Pull at 100 psi (lb) | Adapter | Draw Rod Root Area (sq in) |
|---|---|---|---|
| 3 | About 707 | A | 0.356 |
| 4½ | About 1,590 | A | 0.356 |
| 6 | About 2,827 | B | 0.356 |
| 8 | About 5,026 | B | 0.356 |
| 10 | About 7,854 | C | 0.653 |
| 12 | About 11,310 | C | 0.653 |
| 14 | About 15,394 | C | 0.653 |
| 16 | About 20,106 | C | 1.034 |
| 18 | About 25,447 | C | 1.034 |
| 20 | About 31,415 | D | 1.533 |
💡 Piston rods and adapters in this Standard are designed for stress resulting from air pressures up to 100 psi. They may also be applied to hydraulic cylinders or other power devices, provided working stresses do not exceed those of the corresponding-size air cylinders — always verify the actual driving pressure and pull when sizing.
4. Engineering Practice Essentials 🛠️
- 🔍 Selection workflow: determine the clamping force required by the chuck → back-calculate cylinder bore and supply pressure → select the adapter (A/B/C/D) by bore → verify draw rod thread size and length.
- 🔧 Draw rod length calculation: use the “1 inch + stroke” projection convention to locate the cylinder, measure the distance to the chuck drawbar face, and then determine the total draw rod length — avoiding trial-and-error assembly.
- 📊 Large-bore spindle handling: cylinders 10 inches and larger have larger hubs that provide an additional hole circle on radius N to suit large-diameter spindles; these holes are normally drilled and tapped by the user, not by the cylinder manufacturer, unless ordered.
- 📋 Thread specifications: adapter screw holes are typically UNC-2B and the piston rod end thread is UNF-2B; verify thread series and class before assembly to prevent mismatch.
5. Frequently Asked Questions ❓
❓ Q: What is the relationship between B5.5-1959 and modern standards?
A: B5.5 has been revised several times since the 1932 first edition, and the 1959 edition is one of its most representative historical versions. Modern pneumatic chuck interfaces have moved to newer systems (e.g., ISO interfaces), but the “bore–adapter–draw rod” standardization approach remains fundamental to chuck accessory design.
A: B5.5 has been revised several times since the 1932 first edition, and the 1959 edition is one of its most representative historical versions. Modern pneumatic chuck interfaces have moved to newer systems (e.g., ISO interfaces), but the “bore–adapter–draw rod” standardization approach remains fundamental to chuck accessory design.
❓ Q: Why does pull increase so rapidly with bore size?
A: Thrust equals piston effective area times supply pressure, and area is proportional to the square of the bore. Going from an 8-inch to a 10-inch bore raises the pull from about 5,026 lb to about 7,854 lb. Oversized bores waste pressure and add spindle loading.
A: Thrust equals piston effective area times supply pressure, and area is proportional to the square of the bore. Going from an 8-inch to a 10-inch bore raises the pull from about 5,026 lb to about 7,854 lb. Oversized bores waste pressure and add spindle loading.
🔍 Q: Why does the Standard require piston rod diameters to be as small as possible?
A: To fit spindles with comparatively small holes. A thinner piston rod can pass through a smaller spindle bore, provided it still has sufficient strength and stiffness for the draw rod pull; the Standard balances these two requirements.
A: To fit spindles with comparatively small holes. A thinner piston rod can pass through a smaller spindle bore, provided it still has sufficient strength and stiffness for the draw rod pull; the Standard balances these two requirements.
❓ Q: Do adapters require user machining?
A: Standard adapters have hubs with allowance for the user to bore and thread them to the specific machine spindle. If the standard dimensions are unsuitable, special or user-made adapters are permitted as long as the cylinder interface remains standard and interchangeable.
A: Standard adapters have hubs with allowance for the user to bore and thread them to the specific machine spindle. If the standard dimensions are unsuitable, special or user-made adapters are permitted as long as the cylinder interface remains standard and interchangeable.
