When a workout machine or mechanical equipment is missing a small plastic component, one of the most frustrating challenges is simply not knowing what the part is called. A small cylindrical piece with a flared rim goes by many names — bushing, bearing, grommet spacer, shoulder spacer, top hat bushing, or flanged sleeve bearing — and understanding these terms is the first step toward finding a replacement.
What Is This Part Called?
The small plastic piece commonly found in exercise machines and mechanical assemblies is most frequently referred to as a flanged sleeve bearing or a top hat bushing. The "top hat" nickname comes from its silhouette: a cylindrical body with a wider flange at one end, resembling a top hat when viewed from the side.
Other names used for the same or very similar components include:
- Nylon bushing
- Shoulder spacer
- Grommet spacer
- Kingpin bushing
- Hat bushing
The variation in naming often depends on the industry or application context. In the automotive world, similar parts are called kingpin bushings. In general hardware contexts, "shoulder spacer" or "grommet spacer" are common. Searching across several of these terms when shopping online can significantly broaden the available options.
How to Measure for an Accurate Replacement
Because these parts are manufactured in a wide range of sizes, taking accurate measurements is essential before purchasing. Using a pair of digital calipers is strongly recommended for precision. The key dimensions to record are:
- Inside diameter (ID): The inner bore through which a bolt or shaft passes
- Outside diameter (OD): The outer width of the cylindrical body
- Flange diameter: The wider diameter of the rim at the top
- Flange thickness: The depth/height of the flange portion
- Overall length: The total height of the part including the flange
Having all five measurements on hand makes it far easier to filter through supplier catalogs and find an exact or near-exact match.
A tolerance mismatch — even by a fraction of a millimeter — can result in unwanted movement, noise, or premature wear in load-bearing applications.
Where to Source Replacement Bushings
Several reliable sources carry flanged sleeve bearings and top hat bushings in a wide range of sizes and materials:
| Source | Best For | Notes |
|---|---|---|
| McMaster-Carr (mcmaster.com) | Precise industrial specifications | Extremely wide variety; searchable by exact dimensions |
| Local hardware stores (e.g., Ace Hardware) | Common sizes, immediate availability | Stock varies by location; useful for visual matching |
| Online marketplaces (Amazon, eBay) | Multi-packs, general sizes | Quality varies; check material specifications carefully |
| Specialty bearing suppliers | High-tolerance or load-rated parts | Best for rotational or heavy-load applications |
For fitness equipment specifically, searching the make and model of the machine followed by the word "bushing" in an image search can help visually confirm the correct part before purchasing.
Material and Load Considerations
Bushings used in exercise machines are typically made from engineered plastics such as nylon, acetal (Delrin), or UHMW polyethylene. These materials are chosen for specific functional reasons:
- They are self-lubricating, reducing friction without requiring grease
- They offer consistent dimensional tolerances to minimize mechanical slop
- They resist wear under repeated cyclical loading
When sourcing a replacement, matching the material type — not just the dimensions — can be important. A softer or more brittle plastic substitute may degrade more quickly under the same operating conditions.
Is 3D Printing a Viable Option?
3D printing is occasionally suggested as a quick fix for missing bushings, and while it can work in some low-demand scenarios, there are meaningful limitations to consider for load-bearing applications.
Common FDM (fused deposition modeling) filament printers typically use PLA or PETG, which are generally softer, less dimensionally consistent, and more prone to creep under sustained load than the engineered plastics used in original parts. For bushings that bear rotational or compressive force, a printed replacement may deteriorate relatively quickly.
That said, 3D printing could be considered a temporary solution while a proper replacement is sourced, particularly if the part is not under significant mechanical stress. It is worth noting that this observation is context-dependent and cannot be generalized across all machine types or bushing applications.
Contacting the Manufacturer or Retailer
If the equipment was purchased new and arrived missing components, contacting the manufacturer directly is a reasonable first course of action. Many companies will supply missing parts under warranty or at low cost, even for assembly errors.
In cases where a product has since been discontinued — a situation that can arise with equipment sold through online marketplaces — the manufacturer may still have spare parts inventory, or may be able to provide part specifications that help identify a compatible replacement from a third-party supplier.
When the original manufacturer is unavailable, providing the machine's model number to a local hardware supplier or bearing distributor and asking for a visual match is a practical alternative.
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