QSn4-4-4 Flanged Bushings for Sewing Presser-Lift Rockshafts
Request a QSn4-4-4 flanged bushing for an industrial sewing machine’s presser-lift rockshaft where the original drawing specifies a lubricated bronze sleeve. This is the short-angle lifting linkage, separate from the high-speed main shaft and needle-bar guide.
Balance rockshaft freedom with controlled axial movement
Describe whether the presser lift is driven by a knee linkage, pedal or actuator. Include return-spring torque, angular travel and the adjacent lever positions. A tight sleeve or clamped flange can add drag that prevents full return. Excessive axial movement can instead alter the lever relationship. Show how the shaft is located and where the flange is intended to rub.
QSn4-4-4 should be specified with its wrought-alloy standard, stock form and material condition. Do not recast it as a generic cast-bronze grade or replace it with C93200 from a comparison table. The one-piece machined flange is a construction reference. Establish the lubricant route and shaft finish for the selected material rather than assuming that a bronze surface can run indefinitely without oil.
Application boundaries to confirm
Identify oil leakage paths near fabric and any process restrictions on lubricant or lead-containing materials. A proposed dry composite replacement is a separate design decision, not a finish change to this bronze part. Shaft straightness and support alignment should be checked before reducing running clearance to address linkage play.
Dimensions and drawing-based quotation checklist
| Review item | Information required |
|---|---|
| Sleeve geometry | Bore, OD, body length, flange dimensions and root clearance. |
| Rockshaft stack | Support spacing, lever positions, collars and required axial movement. |
| Motion | Lift angle, return-spring torque, cycle pattern and acceptable friction. |
| Material and order | QSn4-4-4 standard/condition, oil route, contamination limits, quantity and drawing revision. |
Send a dimensioned new-part drawing with units and revision, the mating-part dimensions and requested inspection documents. A worn sample is useful supporting evidence but may not preserve the original fit.
Installation and selection checks
Check that the flange root clears the housing shoulder. Press squarely without bending the flange, then measure the installed fit. Secure collars with the designed axial play and test complete presser lift and return. Apply the specified lubricant sparingly through the intended route and check for migration toward fabric-contact areas.
Frequently asked questions
Does reducing clearance always improve operation?
No. Excessive drag can prevent reliable return; use the mechanism’s approved fit and axial clearance.
Is the product image a QSn4-4-4 material certificate?
No. It illustrates the flanged structure. The material is defined through the accepted order specification.
Can this replace a main-shaft bearing?
That is a different speed and loading requirement and needs a separate bearing review.
Request a custom replacement quotation
Send your drawing to BONIU with the QSn4-4-4 tin bronze requirement, quantity and operating data. We review the specified material route, dimensions and inspection requirements before confirming the quotation.