Two bearings leave the factory with the same “SR144” stamp — yet they sit 0.4 mm apart in width. The standard version measures 2.38 mm and seats cleanly in your rotor. The wide variant is 2.78 mm and jams against the rear cap. Order the wrong one and your turbine simply will not close. Here is how to tell them apart before you buy.
Aftermarket replacement part. Independently manufactured — not supplied by or affiliated with the handpiece manufacturer.
Proof strip: P4 · ISO 9001 · GB/T 30701-2005 · 400,000+ RPM rated · 1,000 h+ bench life
Two ways to get the right bearing
– Contact us for wholesale pricing — clinics, distributors and repair shops buying in volume get wholesale pricing on SR144 and the full SR144 family.
– Send a photo for free identification — not sure which width you need? Send a shot of your old bearing and our technicians confirm the size within one business hour.
SR144 bearing dimensions
An SR144 dental bearing has a 3.175 mm bore and a 6.35 mm outside diameter. Width is the catch: the standard SR144 is 2.38 mm wide, while the SR144…W variant is 2.78 mm wide. Both share the same 144 envelope, so always confirm the width — not just the bore and OD — before ordering.
| Spec | Value | Source |
|---|---|---|
| Bore (ID) | 3.175 mm (0.125 in) | Catalog OCR, all SR144 rows ✅ |
| Outside diameter (OD) | 6.35 mm (0.250 in) | Catalog OCR ✅ |
| Width | 2.38 mm standard / 2.78 mm W variant | Catalog row DS-3K SR144ZZ = 3.175 × 6.35 × 2.78 ✅ + industry suffix table |
| Precision grade | ISO P4 / ABEC-7 | Catalog row GS-S1 shows ISO: P4 ✅ |
| Max speed | 400,000+ RPM rated >580,000 RPM bench limit |
400k = catalog rows GS-A4, GS-S1, GS-N1/N2/N3 ✅ (guaranteed figure). 580k measured at 4.0 kg air pressure, bench only — not a rated operating speed |
| Standard tested to | GB/T 30701-2005 | |
| Quality system | ISO 9001 | |
| Service life | 1,000 h+ at 2.5 kg continuous 500 h+ dry, no-oil |
Bench test data, catalog pp. 2–3 ✅ (two separate protocols — not interchangeable) |
| Ring material | 440C stainless steel | Catalog image extract §1 ✅ |
| Cage material | Torlon / phenolic cage | Catalog image extract §1 ✅ |
| Ball material | 440C steel or Si3N4 ceramic | Catalog image extract §1 (N suffix = Si3N4) ✅ |
| Autoclave | 134 °C compatible | Autoclave spec ✅ |
Speed is a function of air pressure, not a fixed property of the bearing. The same SR144 turns past 420,000 RPM at the 2.2 kg supply pressure most clinics actually run, and past 580,000 RPM at 4.0 kg on the bench — raise the compressor and the number climbs with it. That is exactly why we rate it 400,000+ RPM and not the 580,000 RPM measured at 4.0 kg on the bench. We could print the bigger number; it is a real bench result. But a rated speed has to be what you get at the air pressure in your operatory, not what a test rig hits under load the bearing never sees in service. So when a competitor quotes 500,000 or 600,000 RPM, the first question is not the figure — it is the pressure behind it. A speed claim with no test pressure attached is not a spec you can compare; it is a number you cannot verify.
Buying for a clinic or repair bench? Contact us for wholesale pricing for SR144, SR144W and the full flange/step family — wholesale pricing applies to mixed batches.
SR144 vs SR144…W: why width matters
The “W” at the end of a part number is the single most important character on the line. It stands for wide, and it means the bearing is 2.78 mm across its faces instead of the 2.38 mm default.
Why does 0.4 mm matter? In a dental turbine the bearing sits in a precisely machined seat inside the rotor. The rotor is pressed onto the bearing’s outer ring, and the chuck or cap closes against the bearing’s face. If you fit a 2.38 mm bearing into a seat cut for 2.78 mm, the rotor floats axially, the chuck loses preload, and the handpiece either rattles or fails to spin up. Fit a 2.78 mm bearing where 2.38 mm belongs and it simply will not close — the cap bottoms out before it can clamp.
Decision rule:
– Measure your old bearing across the two flat faces with a vernier or micrometer.
– 2.38 mm → order standard SR144 (no W suffix).
– 2.78 mm → order the W variant (the part number will carry a W).
– When in doubt, send a photo — width varies by head, and the stamp alone does not always tell the full story.
This is the detail most generic suppliers get wrong. They publish one width for every “SR144” and hope it fits. It often does not, which is why returns and comebacks on turbine bearings are so common. If the bearing you are holding sits outside the SR144 envelope, the full dental bearing size chart lists ID, OD and width across the range.
SR144 part number decoder
SR144 part numbers look like alphabet soup, but each letter carries meaning. Use this table to read any SR144-family designation we stock, or run the code through our bearing number lookup if it is not an SR144.
| Code | Meaning | Confidence |
|---|---|---|
| S | Material code prefix | Confirmed (catalog image) |
| F | Thrust shoulder on outer ring (flanged) | Confirmed |
| R144 | Base model — ID 3.175 × OD 6.35 × W 2.38 mm | Confirmed |
| K1 | Inner ring separable (angular contact) | Confirmed |
| K2 | Outer ring separable (angular contact) | Confirmed |
| TA | Polyimide cage (yellow) | Confirmed |
| TL | Polyimide cage (black) | Confirmed |
| Ti | Phenolic resin cage | Confirmed |
| K | Outer ring with step | Confirmed |
| G | Outer ring with groove | Confirmed |
| Z | Shield on one side | Confirmed |
| Z1 | Integral shield on one side | Confirmed |
| W | Width 2.78 mm (both rings) | Confirmed — the money insight |
| W02 | Outer ring 2.38 mm / inner ring 2.78 mm | Confirmed |
| N | Si3N4 ceramic balls | Confirmed |
| (no N) | 440C stainless steel balls | Confirmed |
Width rule: no
WorW02→ 2.38 mm ·W→ 2.78 mm (both rings) ·W02→ outer 2.38 mm / inner 2.78 mm. Ball material: theNsuffix means Si3N4 ceramic balls; withoutN, balls are 440C stainless steel.Timeans a phenolic resin cage — it describes the cage, never the balls, so do not infer ball material fromTi.
SR144 family size chart
The SR144 envelope covers more than a dozen variants — flanged, stepped, shielded and wide. Below are the real catalog rows we carry, with dimensions confirmed by direct read of the product catalog images (PDF pp. 4–7).
| Our PIN | Bearing Model | ID (mm) | OD (mm) | Width (mm) | Notes |
|---|---|---|---|---|---|
| GS-A2 | SR144TLZ | 3.175 | 6.35 | 2.38 | Smooth OD, single shield |
| GS-A4 | SR144TiZ | 3.175 | 6.35 | 2.38 | RPM > 400,000 confirmed |
| GS-A6 | SR144TLZ1N | 3.175 | 6.35 | 2.38 | Smooth |
| GS-D2 | SR144TiKZWN | 3.175 | 6.35 | 2.78 | Stepped/grooved OD variant |
| GS-E1 | SFR144TLZN | 3.175 | 7.5 | 2.38 | Flanged (OD 7.5) |
| GS-E2 | SFR144TiZN | 3.175 | 7.5 | 2.38 | Flanged (OD 7.5) |
| GS-F4 | SFR144TiZ1WN | 3.175 | 7.5 | 2.78 | Flanged (OD 7.5), W = wide |
| GS-F5 | SFR144K1TiGZ1WN | 3.175 | 7.5 | 2.78 | Flanged + groove (OD 7.5) |
| GS-H1 | SFFR144TLGZWN | 3.175 | 7.5 | 2.78 | Double flange/groove (OD 7.5) |
| GS-K1 | SR144TLKZW02N | 3.175 | 6.35 | 2.38 / 2.78 | Stepped OD, W02 variant |
| GS-R1 | SR144TLZW02N | 3.175 | 6.35 | 2.38 / 2.78 | W02 variant |
| DS-3K | SR144ZZ | 3.175 | 6.35 | 2.78 ✅ | Only fully-dimensioned SR144 row |
R144 is the base series code (ID 3.175 × OD 6.35 × W 2.38 mm), not a standalone product — see the suffix decoder above for how the code expands.
Adjacent high-speed bearing sizes (different envelopes, listed for size-chart depth):
| Our PIN | Bearing Model | ID × OD × W (mm) |
|---|---|---|
| GS-S1 | — | 3.175 × 6.0 × 2.0 (P4, >400k RPM) |
| GS-V1 | — | 3.4 × 6.5 × 1.6 |
| GS-N4 | — | 2.38 × 6.35 × 2.78 |
| GS-N2 | — | 2.38 × 5.0 × 1.5 (>400k RPM) |
| GS-P1 | S617TLZN | 3.48 × 7.0 × 2.48 |
| GS-M1/M2 | S628-3 | 3.0 × 7.0 × 2.5 |
Which handpieces use SR144 bearings
SR144-family bearings sit inside high-speed turbine rotors across most major handpiece brands. Fitment varies by model and head size, so confirm the exact part number for your unit before ordering.
- KaVo® compatible bearings — turbines in the 600-series and small-head range
- NSK® compatible bearings — Pana Air and Ti-Max class turbines
- W&H® compatible bearings — Synea TA/TK-class turbines
- Sirona® compatible bearings — T2 and T3-class turbines
- Bien-Air® compatible bearings — Black Pearl and BORA-class turbines
Each hub above carries the model-by-model fitment guide and the cross-reference table for that brand.
Ceramic or steel SR144?
Both materials run in the same SR144 envelope, so the choice comes down to duty and budget rather than fit. Ceramic (Si3N4) balls are roughly 60% lighter than steel and far harder, so they generate less centrifugal load and heat at 400,000+ RPM — they suit busy practices and high-speed, all-day use. Stainless steel costs less and handles moderate use perfectly well; our steel-ball handpiece bearings page sets out where that is the right call. If you want the full material breakdown, see our ceramic dental bearings guide for the side-by-side comparison and which handpieces benefit most.
Send a photo for free identification
Not sure which bearing fits? Don’t guess. Send us a photo of your turbine or your old bearing — our technicians identify the correct size and part number within 1 business hour.
Include the head-size stamp if visible — width varies by head.
Send it through our free bearing identification service — no account needed, and there is no obligation to order afterwards.
Ready to order? Contact us for wholesale pricing for SR144 and the full family — wholesale pricing for clinics, distributors and repair shops. Not sure of the width? The photo-ID service above is free.
FAQ
What size is an SR144 bearing?
An SR144 dental bearing has a 3.175 mm bore and a 6.35 mm outside diameter. The width is the variable: the standard SR144 is 2.38 mm wide, while the SR144W (any part number carrying the W suffix) is 2.78 mm wide. Always measure your old bearing’s width before ordering.
What’s the difference between SR144 and SR144…W?
They share the same 3.175 × 6.35 mm envelope, but the W suffix denotes a wide version that is 2.78 mm across the faces instead of 2.38 mm. The wider bearing fills a deeper rotor seat; a standard-width bearing will not seat correctly in a wide rotor, and vice versa.
Ceramic or steel SR144 — which should I buy?
Ceramic (Si3N4) balls run cooler under high speed; stainless steel costs less and suits moderate use. For the full comparison, see our ceramic dental bearings guide. Match the choice to your handpiece’s duty cycle and budget.
How do I know my SR144 bearing is worn out?
Watch for a gritty or noisy spin, visible play in the chuck, vibration at speed, or a turbine that fails to reach full RPM. Any of these usually means the bearing has lost its preload or the balls have pitted. Replace both front and rear bearings together.
How do I replace an SR144 bearing?
Press the old bearing out of the rotor with a proper bearing extractor, clean the seat, and press the new one in squarely using a pilot tool. Work on a clean bench, keep the shields dry, and confirm free rotation before reassembling the turbine.
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Related pages
- Dental turbine bearings — the parent category and full range overview
- Ceramic dental bearings — ceramic vs steel material comparison
- Bearing cross-reference lookup — match your old part number to ours
All brand names are trademarks of their respective owners, used solely to identify compatible applications. Products are independently manufactured and not OEM parts.
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