Beskrivning
EP6-20 Set Screw Oldham Coupling — 20 mm Three-Piece Slider for Mid-Range Servo and Stepper Drives
De EP6-20 Oldham coupling bridges the gap between sub-newton-meter precision instruments and the mid-range servo drives found in benchtop automation. With a 20 mm outside diameter, a 30 mm overall length, and bore options that span the metric 6 mm / 8 mm shaft sizes and the imperial 6.35 mm (1/4″) standard, this set-screw model is the most ordered SKU in the EP6 family — the workhorse that quietly connects countless desktop CNC routers, pick-and-place heads, peristaltic pumps, and motorised valve actuators to their drive motors.
The mechanical design preserves the defining traits of the Oldham architecture: a three-piece sandwich of two aluminum-alloy hubs surrounding a polyacetal centre disc, two orthogonal sliding interfaces that decompose parallel misalignment into pure translational motion, and a constant-velocity 1:1 torque transmission with zero rotational backlash. What changes versus the smaller EP6-16 is the absolute torque envelope (1.6 N·m rated, 3.2 N·m peak) and the inertia footprint (9.0 × 10⁻⁷ kg·m²) — both still favourable for closed-loop servo systems, but now sized for NEMA 14 / NEMA 17 / Φ28 mm BLDC motor outputs.
Specifikationer
| Parameter | Värde |
|---|---|
| Modell | EP6-20 |
| Ytterdiameter (ΦD) | 20 mm |
| Total längd (L) | 23 mm |
| Borrningsområde (d1 / d2) | 6, 6.35, 8 mm |
| Nominellt vridmoment | 1.6 N·m |
| Maximalt vridmoment | 3.2 N·m |
| Maximal rotationshastighet | 7 400 rpm |
| Tröghetsmoment | 9.0 × 10⁻⁷ kg·m² |
| Statisk vridstyvhet | 58 N·m/rad |
| Parallell feljustering | 1.4 mm |
| Vinkelfeljustering | 3,0° |
| Gänga för ställskruv | M4 |
| Åtdragningsmoment för skiftnyckel | 1.7 N·m |
| Massa (max borrning) | 14 g |
| Glapp | Noll |
Material
A2017 Aluminum-Alloy Hubs
Both outer hubs are machined from A2017 aluminum and clear-anodised for corrosion resistance. The alloy strikes the right balance between machinability and yield strength for set-screw seating — fastener torque can be applied to specification without deforming the bore. Heat dissipation, while rarely a limit for the EP6-20, is excellent: the entire coupling reaches thermal equilibrium with ambient within minutes, even after duty bursts.
Engineering POM Slider
The centre disc is engineered polyacetal (POM-C copolymer), the workhorse polymer for sliding plain-bearing duties. It is self-lubricating against aluminum, electrically insulating across a 12 kV/mm dielectric, and stable from −40 °C to +100 °C. For applications that demand higher torsional rigidity or impact tolerance, a 30 % glass-fibre filled grade can be substituted — please mention “GF-POM slider” at the time of enquiry.
M4 Stainless Set Screws
Hex-socket SUS304 M4 set screws — two per hub at 90° — secure each shaft. The 1.7 N·m wrench torque specification gives a generous safety margin against slip at rated load, while still being achievable with a pocket-sized 2.0 mm hex key.
How the EP6-20 Compensates Misalignment
Picture two parallel motor shafts 100 mm apart, both pointing in the same direction, but offset radially by 1.0 mm — the kind of stack-up that emerges naturally when a stepper motor is bolted onto a bent sheet-metal bracket. A rigid coupling would transmit this offset into the load bearing as a continuous radial force, accelerating bearing fatigue and producing a measurable side-load on the motor’s own ball races. A bellows coupling would absorb the offset elastically — but with a restoring force that is bidirectional, oscillating, and that injects a torsional ripple into the loop at the shaft frequency.
The EP6-20 handles the same 1.0 mm offset differently. The polyacetal slider’s two orthogonal tongues simply translate inside the two hub slots — one tongue slides “north-south”, the other “east-west” — and the slider’s centre point traces a small circular orbit at the shaft speed. Crucially, the angular velocity that exits Hub B is identical to the angular velocity that enters Hub A: there is no second-harmonic ripple, no torsional spring, and (with set-screws properly tightened) no backlash. The work of misalignment compensation is dissipated as a very small amount of sliding friction inside the slider — typically <1 % of transmitted torque under normal operation.
This makes the EP6-20 particularly useful in closed-loop encoder-feedback systems, where any elastic compliance between motor and encoder shows up as a phase lag in the velocity controller. With an Oldham coupling the encoder sees the load shaft’s true motion, not a filtered version of it.
Industritillämpningar
️ Desktop CNC & Hobby Mills
Linking NEMA 17 steppers to 8 mm ball-screws on benchtop 3- and 4-axis mills. The 1.4 mm parallel tolerance gives slack to absorb cabinet flex during heavy cuts.
Pharmaceutical Dispensing Pumps
Driving the rotor of peristaltic and gear-meter dispensing heads. POM’s electrical insulation eliminates galvanic coupling between fluid path and chassis ground.
Light-duty Robotics
Joints in collaborative-robot teaching units and educational arms. Constant-velocity transmission preserves the trajectory accuracy that learning algorithms depend on.
Motorised Valves & Actuators
Linking the actuator drive shaft to butterfly and ball-valve stems in process automation skids. Tolerates the cumulative misalignment of multi-housing valve trains.
️ Food-machinery Conveyor Drives
Light conveyor segments and metering augers in confectionery and bakery lines, where wash-down water can reach the coupling. POM is FDA-listed and copes with intermittent immersion.
️ Industrial Inkjet & Marking Heads
Connecting traverse motors to belt pulleys in date-coding and product-marking units. Constant-velocity is critical to maintain even pixel pitch in the printed text.
Why Choose Ever-power for Your EP6-20 Couplings
Certified Quality System
Ever-power operates under an ISO 9001:2015 quality management system. All EP6-20 production batches carry full material traceability — aluminum melt-cast lot numbers, POM resin batch IDs, and stainless-fastener heats — backed by RoHS-riktlinjer and NÅ conformity statements. CE documentation can be supplied where the coupling is incorporated into machinery for the European market.
Customisation Beyond Catalogue
The catalogue bore set (6 / 6.35 / 8 mm) covers most NEMA 17 and Φ8 mm shafts, but mixed bores (e.g., 6 mm × 8 mm), keyway-broached bores, D-cut shaft mating, and oversized OD variants are produced regularly. Anodised colours can be matched for product-line branding.
Logistics & Support
English-speaking application engineers reply within 24 timmar on selection, drawing, and de-rating queries. For repeat MRP buyers, Ever-power maintains a Kanban buffer of standard EP6-20 bore combinations to keep replenishment under two weeks even during the Asian holiday calendar.
Kundrecensioner och fallstudier
★★★★★
Italy — Pharmaceutical Filling Line OEM
Används i: Pump drive on a vial-filling skid running 24/6 production shifts.
Feed-back: “Sliding-disc design has been working flawlessly for 14 months across 18 dispensing channels. The previous flexible-jaw coupling needed elastomer replacement every six months; EP6-20 has eliminated that maintenance task entirely. Documentation pack was complete on first delivery, which saved us a back-and-forth with QA.”
★★★★★
Mexico — Industrial Inkjet Manufacturer
Används i: Traverse drive of a continuous-jet date-coder.
Feed-back: “We moved to the EP6-20 from a competitor’s bellows after the bellows fatigue-cracked at 16 months. Two years in on the EP6-20, no failure, and our printed-character vertical alignment is visibly more consistent. Worth the slightly higher unit price.”
★★★★☆
Canada — Educational Robotics
Används i: Joints of an open-source 5-axis teaching arm distributed to vocational colleges.
Feed-back: “Students assemble and disassemble these arms hundreds of times per semester. The EP6-20 survives much better than the cheaper clamp couplings we used to source locally. One star removed only because we wish the keyway option were available off the shelf — but Ever-power did produce it as a custom request within their stated lead time.”
Vanliga frågor
Will the EP6-20 work with imperial 1/4-inch shafts?
Yes. 6.35 mm is the cataloged equivalent of a 1/4-inch shaft and is one of the three standard bore options. Mixed-bore versions (e.g., 6.35 mm × 8 mm) are also produced on request without affecting catalogue lead time.
How much radial load does it transmit to the motor bearings?
For a 1.0 mm offset at rated torque, the radial reaction on the motor bearing is typically below 5 N — an order of magnitude below the static load capacity of a NEMA 17 motor’s front ball bearing. The Oldham architecture is the only common flexible coupling that achieves this so consistently.
Can I use thread-locker on the M4 set screws?
Yes — a low-strength formulation such as Loctite 222 is recommended for vibration-prone installations. Avoid medium-strength threadlocker (Loctite 243) unless servicing access is not a concern, since 243 can require localised heating to release the M4 screws.
What happens if the rated torque is briefly exceeded?
The EP6-20 tolerates peaks up to 3.2 N·m without permanent damage. Repeated peaks above that level will accelerate slider wear; sustained operation above 1.6 N·m is not recommended. For peak demands above 3.2 N·m we suggest stepping up to the EP6-25.
Do you offer FDA-compliant variants for food contact?
Standard POM resin used in the slider is FDA-listed (21 CFR 177.2470) for incidental food contact. For direct prolonged contact we recommend specifying a food-grade PEEK slider — please mention “FDA-direct-contact” at enquiry stage so engineering can supply the appropriate declaration.
Get a Quote & Engineering Drawing
Procurement engineers across the Americas, EMEA, and APAC trust the EP6-20 for repeat MRP buys at scale. Browse the rest of our Oldham-kopplingskatalog for adjacent sizes, learn about our global supply network, or move straight to a tailored quote below.
