Through-bore slip rings
Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)
Through-bore slip rings rated 5 to 10 A at 500 to 600 V AC, with bores of 0.503 to 1.50 in (12.8 to 38.1 mm) and 250 to 600 rpm; SR017 and SR018 are sealed to IP65.
Key specifications
| Current per circuit (max) | 10 A |
|---|---|
| Voltage (max) | 600 V |
| Speed (max) | 600 rpm |
| Bore | 12.8–38.1 mm |
| Ingress protection | IP65 (sealed SR017/SR018) |
Summarised in our own words from Rotary Systems Inc.'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Bores converted from inches.
Specify Motion is not affiliated with Rotary Systems Inc.. Rotary Systems and Through-bore capsules and sealed rings (SR013–SR018) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Rotary Systems part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These series from our supply network is the closest match on published figures.
Through-bore slip rings with a hollow centre so shafts, pipes or cables can pass through, carrying power, signal and fieldbus data. Standard bores run from 12.7 mm to 100 mm and custom bores are offered.
| Published maximum | Through-bore capsules and sealed rings (SR013–SR018) | ER Series Through Bore Slip Ring |
|---|---|---|
| Circuits | — | 24 |
| Current per circuit | 10 A | 15 A meets or exceeds |
| Speed | 600 rpm | 300 rpm |
| Voltage | 600 V | 380 V |
| Bore | 38.1 mm | 100 mm meets or exceeds |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a through-bore slip ring is
A through-bore slip ring is a rotary electrical joint built around a hollow centre, so a drive shaft, pneumatic or hydraulic line, fibre or cable bundle can pass straight through it. The rings are mounted on an insulated sleeve that fits over or around the machine shaft, and the brush blocks sit outside them in a stationary housing. Power, signal and data circuits are combined in one unit, while the bore keeps the rotation axis available for mechanics or services. Bore sizes range from a few millimetres to hundreds of millimetres.
When engineers choose a through-bore slip ring
Engineers choose a through-bore design when the axis of rotation is already occupied, typically by a shaft, a rotary union or a cable that must stay continuous. It is the standard choice for indexing tables, wrapping machines and turntables built around a central column. The trade-off is that larger rings mean higher surface speed, more brush wear and more drag torque at the same rpm, and the unit is bigger than a capsule. Where axial length is the constraint rather than diameter, a pancake design may suit better.
How to specify the Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)
Send these with your enquiry and an engineer can confirm the right Through-bore capsules and sealed rings (SR013–SR018) variant or an equivalent:
- Bore diameter and shaft tolerance (mm)
- Outer diameter and length limits (mm)
- Circuit count and current per circuit (A)
- Working voltage and any high-voltage isolation (V)
- Speed, continuous and peak (rpm)
- Data or bus protocols to pass, such as Ethernet, CAN or PROFINET
- Sealing (IP code), temperature (°C) and mounting method
Common mistakes to avoid
- Sizing the bore to the shaft only, with no allowance for a rotary union or cables that must also pass
- Mounting the rotor hard on a shaft with radial runout and a separate stator fixing, so the unit is forced to align two axes
- Forgetting that surface speed rises with diameter, so the rated rpm is lower for larger bores
- Not stating which circuits need screening or twisted pairs for encoder and fieldbus signals
Rotary Systems Through-bore capsules and sealed rings (SR013–SR018): frequently asked questions
What is the Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)?
Through-bore slip rings rated 5 to 10 A at 500 to 600 V AC, with bores of 0.503 to 1.50 in (12.8 to 38.1 mm) and 250 to 600 rpm; SR017 and SR018 are sealed to IP65. Published series figures include current per circuit 10 A, voltage 600 V, speed 600 rpm, bore 12.8 mm. It is made by Rotary Systems Inc.; Specify Motion can help source it or propose an equivalent.
Who makes the Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)?
The Rotary Systems Through-bore capsules and sealed rings (SR013–SR018) is made by Rotary Systems (Rotary Systems Inc.) and is listed here for engineers comparing options. Specify Motion is not affiliated with Rotary Systems Inc.; brand names are used only to identify the product.
What is the current per circuit of the Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)?
The published series maximum current per circuit is 10 A. Individual models and sizes in the Through-bore capsules and sealed rings (SR013–SR018) range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Rotary Systems Through-bore capsules and sealed rings (SR013–SR018)?
Yes. On published figures, ER Series Through Bore Slip Ring is the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
How do I choose the bore size for a through-bore slip ring?
Start with the shaft diameter and its tolerance, then add anything else that must pass through the centre, such as hoses, a rotary union stem or a fibre. Allow clearance for assembly and for the insulating sleeve. Larger bores raise surface speed, cost and drag torque, so pick the smallest bore that genuinely clears what has to pass through.
Can a through-bore slip ring carry Ethernet as well as power?
Yes. Many through-bore units combine power rings with signal rings designed for industrial Ethernet, using controlled impedance, twisted-pair routing and screening between groups. State the protocol and speed, typically 100 Mbit/s or gigabit, so the supplier can allocate suitable rings and keep them away from motor power. For very high data rates, a contactless or fibre channel may be added.
Further reading: How to select a slip ring · Ethernet through slip rings · Slip rings
Other through-bore slip rings series
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