NAP200 Series Pillow Block Bearing Units — Eccentric Collar Locking for Unidirectional Drives
Machines that run continuously in one direction place a specific and underappreciated demand on their shaft-to-bearing interface: the locking mechanism must resist not just radial load, but the cumulative micro-movement that builds up over millions of shaft revolutions and gradually loosens a conventional setscrew. The NAP200 series addresses this directly. Its eccentric locking collar converts shaft rotation torque itself into clamping force — meaning the harder and longer the shaft runs, the more securely the collar grips. The NAP200 housing envelope is dimensionally identical to UCP200, making it a zero-modification retrofit wherever setscrew loosening has become a recurring maintenance issue.
The Eccentric Collar — Mechanism & Retention Logic
The NAP200 insert bearing extends its inner ring axially on one side to form an integral eccentric collar. The collar bore is offset from its outer cylindrical surface by a small geometric eccentricity. When the collar is rotated in the direction of shaft rotation and its locking screw is tightened, this offset causes the collar bore to cam radially inward, applying clamping pressure around the shaft circumference. As the shaft spins in service, friction at the collar-shaft interface acts to tighten the collar further — a self-reinforcing retention characteristic that setscrews fundamentally cannot replicate.
A setscrew creates localised point-contact pressure that is gradually undermined by fretting corrosion, micro-slip, and vibration over extended duty cycles. On a pump running 3000 hours per season or a fan that operates continuously between scheduled shutdowns, the difference between setscrew and eccentric collar retention translates directly into bearing replacement frequency and unplanned downtime cost.
Key Features
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Self-Tightening Eccentric Collar
Collar grip intensifies with shaft rotation, not against it — provides sustained retention on long-running unidirectional drives without periodic re-torquing.
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UCP200-Identical Housing Footprint
Same H, L, J, A dimensions as UCP200 for equivalent bore. Direct retrofit into existing machine structures — no frame drilling, guard modification, or shaft alteration required.
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No Shaft Preparation Required
Fits standard ground or turned shafts at h9 tolerance. No keyway, flat, or groove required. Collar engagement area is distributed, reducing shaft surface stress versus setscrew point contact.
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Wider Inner Ring Insert
UC series wide inner ring accommodates axial shaft float while maintaining radial load capacity equivalent to the UCP200 at each bore size.
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Hollow Base Standard / Solid Base Option
Hollow base reduces weight for standard applications. Solid base (suffix SB) available for high belt-tension or impact-loaded mountings on request.
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Full Metric & Inch Bore Coverage
Each metric housing size accommodates multiple inch bore inserts. Shaft range 12–75 mm covers the majority of agricultural and industrial drive applications where eccentric locking is appropriate.
Full Dimensional Specifications
| Unit No. | d mm | d inch | H mm | L mm | J mm | A mm | N mm | N₁ mm | H₁ mm | H₀ mm | B₁ mm | S mm | Bolt | kg |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NAP201 / 201-8 | 12 | 1/2 | 30.2 | 127 | 95 | 38 | 13 | 19 | 14 | 61 | 43.7 | 17.1 | M10 | 0.72 |
| NAP202 / 202-9 / 202-10 | 15 | 9/16, 5/8 | 30.2 | 127 | 95 | 38 | 13 | 19 | 14 | 61 | 43.7 | 17.1 | M10 | 0.72 |
| NAP203 / 203-11 | 17 | 11/16 | 30.2 | 127 | 95 | 38 | 13 | 19 | 14 | 61 | 43.7 | 17.1 | M10 | 0.72 |
| NAP204 / 204-12 | 20 | 3/4 | 33.3 | 127 | 95 | 38 | 13 | 19 | 14 | 64 | 43.7 | 17.1 | M10 | 0.72 |
| NAP205 / 205-14/15/16 | 25 | 7/8, 15/16, 1 | 36.5 | 140 | 105 | 38 | 13 | 19 | 15 | 71 | 44.4 | 17.5 | M10 | 0.80 |
| NAP206 / 206-17/18/19/20 | 30 | 1-1/16 ~ 1-1/4 | 42.9 | 160 | 121 | 44 | 17 | 21 | 16 | 82 | 48.4 | 18.3 | M14 | 1.35 |
| NAP207 / 207-20/21/22/23 | 35 | 1-1/4 ~ 1-7/16 | 47.6 | 167 | 126 | 48 | 17 | 21 | 17 | 92 | 51.1 | 18.8 | M14 | 1.70 |
| NAP208 / 208-24/25 | 40 | 1-1/2, 1-9/16 | 49.2 | 180 | 137 | 52 | 17 | 21 | 18 | 99 | 56.3 | 21.4 | M14 | 2.00 |
| NAP209 / 209-26/27/28 | 45 | 1-5/8 ~ 1-3/4 | 54 | 190 | 146 | 54 | 17 | 21 | 20 | 106 | 56.3 | 21.4 | M14 | 2.42 |
| NAP210 / 210-30/31/32 | 50 | 1-7/8 ~ 2 | 57.2 | 206 | 159 | 60 | 20 | 25 | 21 | 114 | 62.7 | 24.6 | M16 | 2.75 |
| NAP211 / 211-32/34/35 | 55 | 2 ~ 2-3/16 | 63.5 | 217 | 172 | 60 | 20 | 25 | 23 | 125 | 71.4 | 27.8 | M16 | 3.56 |
| NAP212 / 212-36/38/39 | 60 | 2-1/4 ~ 2-7/16 | 69.9 | 238 | 186 | 70 | 20 | 25 | 24 | 137 | 77.8 | 31 | M16 | 5.20 |
| NAP213 / 213-40 | 65 | 2-1/2 | 76.2 | 262 | 203 | 70 | 25 | 30 | 26 | 149 | 85.7 | 34.3 | M20 | 6.30 |
| NAP214 / 214-44 | 70 | 2-3/4 | 79.4 | 266 | 210 | 72 | 25 | 30 | 27 | 155 | 85.7 | 34.3 | M20 | 7.00 |
| NAP215 / 215-47/48 | 75 | 2-15/16, 3 | 82.6 | 274 | 217 | 74 | 25 | 30 | 28 | 162 | 92.1 | 37.3 | M20 | 7.80 |
→ Scroll table horizontally to view all columns. B₁ = eccentric collar width (wider than standard B — check axial clearance). Not suitable for reversing or oscillating shaft drives. Solid base: suffix SB. Grease at 45° standard; 90° on request.
NAP200 vs UCP200 — Selection Guide
- Shaft rotates in one direction only
- Drive runs continuously for long periods
- Vibration level is moderate to high
- Setscrew loosening is a recurring issue
- Extended re-torquing intervals are required
- Shaft direction reverses during operation
- Drive is intermittent with frequent start/stop
- Bore sizes above 75 mm are needed
- Oscillating motion is present
Applications
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Irrigation & Pump Drives
Centrifugal pump shafts running 3000–5000 hours per season at 1450–2900 rpm. NAP210–NAP212 eliminates inner ring creep on 50–60 mm pump shafts without modifying the pump skid structure.
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Grain Auger & Elevator Drives
Variable-load auger shafts where torque fluctuates between empty running and peak throughput with wet grain. NAP206–NAP207 on 30–35 mm shafts maintains grip through load cycles that loosen setscrews within a season.
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Continuous Fan & Ventilation
Industrial fans running between scheduled shutdowns — weeks or months at a time — where a setscrew re-check is not practical. Eccentric collar retains grip without operator intervention over the full run period.
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Conveyor Tail Pulleys
Belt conveyor tail pulley shafts under sustained radial load from belt tension. Eccentric collar tightens as the belt pulls the pulley, making NAP200 inherently more stable than setscrew retention in this load direction.
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Combine Threshing & Harvesting
Threshing cylinder and straw walker shafts running continuously during harvest. High vibration from crop impact makes these ideal NAP200 applications where setscrew retention is routinely insufficient.
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Process Machinery Retrofit
Drop-in upgrade from UCP200 on any existing machine with a history of setscrew loosening. No frame modification required. Specify NAP in place of UCP with the same bore code to upgrade in the next maintenance cycle.
📦 MOQ & Order Information
- Standard parts: quantity-based MOQ applies per model number.
- High-value / large items: minimum order by USD order value.
- New-client samples: 1–5 pcs available at sample price for first-time buyers.
- Multi-model combines: aggregate orders of USD 1,500 or more across models accepted.
- Special materials / processes: subject to process MOQ — confirm at inquiry stage.
- Retail (1–2 pcs): not accepted. Minimum sample order is 1–5 pcs at sample pricing.
Detailed engineering drawings must be submitted and approved before order confirmation. Catalogue dimensions are for reference only.
Collar Installation Procedure
Slide the unit onto the shaft to the required axial position with the collar locking screw finger-loose. Hold the housing stationary and rotate the eccentric collar in the intended shaft rotation direction until it reaches its mechanical hard stop. Tighten the collar locking screw to the torque specified in the confirmed engineering drawing. Do not substitute higher locking screw torque for correct collar rotation — a collar not fully seated at its hard stop will not achieve rated clamping force regardless of screw torque. Check locking screw torque after the first 8–24 hours under full load. For comparison with the concentric locking collar variant suited to high-speed applications, see the UEP200 concentric locking series. For applications where shaft preparation must be avoided entirely, refer to the UKP200+H adapter sleeve series.
Frequently Asked Questions
Can NAP200 be used on a reversing drive?
No. Reverse rotation progressively releases the eccentric collar grip. Use UCP200 setscrew units for any application involving shaft reversal or oscillating motion.
Is NAP200 dimensionally interchangeable with UCP200?
Yes. Housing external dimensions H, L, J, A are identical to UCP200 for each equivalent bore. Direct bolt-in retrofit — no frame, guard, or shaft modification required.
Why does the spec table show B₁ instead of B?
B₁ is the width across the eccentric collar, which projects axially beyond the standard insert shield face. Check this dimension against available axial space before mounting units in close proximity.
What is the minimum order quantity?
Standard parts: quantity-based MOQ. New-client samples 1–5 pcs at sample price. Multi-model orders combined from USD 1,500. Retail 1–2 pcs not accepted. Engineering drawings required before confirmation.
Request a Quote for NAP200 Series
Provide shaft diameter, rotation direction, operating speed, and estimated daily running hours. This allows confirmation of NAP200 suitability before order. Contact us.
