SF-1 PTFE Split Bushings for Internal-Gear-Pump Drive Shafts
For an SF-1 PTFE composite split bushing supporting an internal-gear-pump drive shaft, specify installed bore size and bore position separately. Confirm whether the exact lining permits any finishing after installation. A proprietary machinable pump bearing does not establish permission to ream a generic SF-1 sleeve. Release the material, housing datums, shaft and fluid conditions as one pump-bearing system.
This article concerns the drive-shaft journal supports in an existing internal-gear-pump design or an approved design study. The sleeve is not the gear tooth surface, crescent seal or axial pressure plate. Do not treat a bushing replacement as a complete pump rebuild specification.
Connect the journal supports to the gear-set position
GGB’s internal-gear-pump application note links drive-shaft position to the internal gears, crescent-shaped seals and noise behaviour. It describes two plain bearings operating under varying speed, temperature and fluid viscosity. The note discusses its DTS10 product; it is application context rather than proof of an SF-1 replacement.
[1]Identify both journal supports and their relationship to the pump’s locating features. Record the shaft axis, gear-set datums and the housing machining or assembly sequence. A bearing measured in isolation cannot establish the shaft position relative to the rest of the pump.
Obtain the pump designer’s bearing reactions for the relevant operating states. Hydraulic circuit pressure is not itself journal contact pressure. Include the direction and variation of loads, starts, reversals where applicable and the permitted dry or boundary-lubrication transients. Do not assign a generic pressure-speed limit to an unspecified sleeve.
Separate a bore-size pass from a datum-location pass
The following original inspection example uses assumed dimensions and acceptance criteria. It is not a recommended pump fit. Let the shaft diameter range be 24.990–25.000 mm and the installed bushing bore range be 25.025–25.040 mm. The resulting diametral running clearance spans 0.025–0.050 mm.
| Inspection item | Assumed requirement or calculation | Interpretation |
|---|---|---|
| Minimum diametral clearance | 25.025 − 25.000 | 0.025 mm |
| Maximum diametral clearance | 25.040 − 24.990 | 0.050 mm |
| Installed bore location | Example maximum centre offset: 0.020 mm from the specified datum axis | A separate acceptance criterion |
| Measured centre offset | Example measured offset: 0.040 mm | Fails the assumed location criterion even if diameter passes |
This example shows two independent inspection decisions. It does not predict pump noise, efficiency or seizure. A complete drawing must define the location measurement and its datums, as well as roundness, alignment, inspection temperature and other required geometric controls.
Do not subtract a quoted centre offset from a diametral clearance and call the remainder a validated operating margin. Their relationship depends on the two-support arrangement, shaft constraints, clearance distribution and operating deflection. Evaluate the assembled geometry rather than combining unrelated tolerance numbers.
Keep post-installation machining specific to the lining
GGB describes DTS10 as a pump-bearing system with a defined overlay that permits machining of its assembled bore. Its DU product page separately describes a steel-backed porous-bronze/PTFE-and-lead material and directs machining questions to application engineering. These are different manufacturer product descriptions.
[1][2]| Proposed action | Evidence needed before approval | Remaining acceptance |
|---|---|---|
| Use a prefinished SF-1 sleeve | Supplier’s installed dimensional method and fit instructions | Mounted size, location and condition |
| Finish the bore after pressing | Written permission for the exact lining and remaining working layer | Approved process, geometry and surface inspection |
| Replace with a proprietary machinable bearing | Approved material and design substitution | Compatibility, installed geometry and pump validation |
| Correct a mislocated housing bore | Designer-approved housing repair | Restored datum relationship and retention |
A drawing note saying “PTFE composite” does not define machining allowance. Reaming, scraping or honing may alter the working layer and its support. Do not use a cutting operation to conceal an incorrect housing seat or apply another product’s process permission to the supplied sleeve.
State the backing, interlayer, sliding mixture, total thickness and outside finish. DU is a protected GGB product designation; an SF-1 family description does not establish that brand, its composition, certification or test history. Confirm any lead-content restriction for the actual order.
Preserve the oil route and inspect the mounted sleeve
Identify how the intended hydraulic fluid reaches and leaves the journal interface. Mark feed holes, grooves, restrictions and their orientation on the controlled drawing. Include the fluid specification, viscosity information over the operating temperature range, contamination condition and compatibility requirements.
Keep the pump’s required priming, filling, venting and start-up procedures. A dry-running bearing description is not permission to run a hydraulic pump without its specified fluid. Any change to a groove, feed or running gap can affect more than bearing friction and needs the pump designer’s review.
Prepare the housing entries, use supported insertion tooling and protect the thin lining from burrs. Align any specified seam and feed features. Measure the installed bores and datum relationships after assembly, and verify the actual shaft condition. Plating colour and free-state sleeve diameter do not establish the completed interface.
Agree what a replacement trial must demonstrate
Set separate acceptance stages for material documentation, dimensional inspection and the assembled pump. For the functional stage, agree the relevant speed, pressure, fluid temperature, start-up and steady operating conditions, together with the required observations and stop criteria.
Assess the pump maker’s specified performance checks, which may include flow, leakage, noise, temperature and post-test wear. Record the assembly and test conditions. No improvement in noise or efficiency, life prediction or application approval is promised from an SF-1 material change alone.
The purchasing decision should identify whether the request is for a like-for-like sleeve, an approved alternative material or a housing-and-bearing repair. Those scopes require different evidence and should not be collapsed into a nominal ID × OD × length enquiry.
Frequently asked questions
Can an SF-1 sleeve be reamed because a pump bearing catalogue permits it?
Only the permission for the exact supplied construction applies. A proprietary machinable lining does not establish a generic SF-1 machining allowance.
Does an acceptable installed diameter prove correct shaft position?
No. The bore’s datum relationship and the two-support geometry require separate inspection.
Can a dry-running bushing eliminate the pump’s hydraulic oil requirement?
No. Follow the pump’s approved fluid and commissioning requirements. The bearing description does not replace the hydraulic-system specification.
Request a drawing review
Send the pump section, both bearing seats and datums, shaft limits, installed bore and location requirements, proposed lining specification, machining plan if any, fluid and temperature data, bearing reactions, operating sequence, quantity and functional acceptance criteria.
Send your drawing for review or email sales@boniubushing.com. BONIU confirms material availability, manufacturing feasibility and inspection scope for each enquiry. This guide does not establish stock, certification, application approval or BONIU test results.
Technical references
- GGB: Internal gear pumps and motors. DTS10 shaft-position and machining context; proprietary capability is not transferred to SF-1.
- GGB: DU metal-polymer bearings. Material identity, protected designation and material-specific machining consultation.
Published data apply to the manufacturer, product form and conditions identified by the source. Original examples and application checklists here are engineering analysis, not BONIU product ratings. Final supply and acceptance follow the agreed drawing and material specification.