Summary
Ball transfer units are available in five main mounting styles: flanged (bolted via a flat flange), threaded stem (screwed into a threaded hole), drop-in or press-fit (pushed into a drilled hole for a flush finish), clamped (secured externally), and base fixing (mounted from underneath).
Flanged, Threaded, Drop-In, Clamped and Base Fixing — A Practical Comparison
Ball transfer units are available in five main mounting styles: flanged (bolted via a flat flange), threaded stem (screwed into a threaded hole), drop-in or press-fit (pushed into a drilled hole for a flush finish), clamped (secured externally), and base fixing (mounted from underneath).
The right choice depends on your mounting surface, access requirements, and whether a flush top surface is needed.
Mounting style is one of the most practical decisions in ball transfer unit selection. It determines how the unit is installed, how easily it can be replaced, and what the finished surface looks like. This guide compares the five main options so you can choose with confidence.
Flanged Mounting
Flanged ball transfer units have a flat collar around the housing with two or more bolt holes. The unit is secured to the mounting surface using screws or bolts passed through these holes.
Advantages
• Extremely secure — the bolted connection resists vibration and lateral forces
• Easy to install and remove for maintenance or replacement
• Visible fixings make it easy to confirm the unit is properly secured
• No precision-drilled hole required — clearance holes and bolts are sufficient
Best For: Heavy-duty applications, ball transfer tables subject to high loads or vibration, installations where easy maintenance access is a priority, and retrofitting BTUs to existing surfaces.
Considerations
The flange sits proud of the mounting surface, which means the fixings are visible and the top surface is not completely flush. If a smooth, uninterrupted surface is required, drop-in or base fixing may be preferable.
Threaded Stem (Stud/Bolt) Mounting
Threaded stem ball transfer units have a threaded shaft extending from the base of the housing. This shaft screws directly into a threaded hole in the mounting surface.
Advantages
• Compact — no flange means the unit takes up minimal space
• Clean appearance with only the ball housing visible above the surface
• Height-adjustable by screwing the stem further in or out
• Simple installation into pre-threaded holes
Best For Conveyor frames, machine tables, jig plates, and any application where space is limited and a clean profile is desired. Also useful where slight height adjustment is needed during installation.
Considerations
Requires a threaded hole in the mounting surface, which means the surface must be thick enough to accept the thread. Removal for maintenance requires unscrewing the unit, which can be slower than unbolting a flanged unit.
Drop-In (Press-Fit / Interference Fit) Mounting
Drop-in ball transfer units are designed to be pressed into a precision-drilled hole in the mounting surface. The unit is held in place by an interference fit — the outer diameter of the housing is fractionally larger than the hole, creating a tight, secure friction fit.
Advantages
• Completely flush top surface — no fixings, flanges, or protrusions visible
• Fast installation — simply press or tap the unit into the hole
• Clean, professional appearance ideal for ball transfer tables
• No fasteners to loosen over time
Best For: Ball transfer tables, workstations, and platforms where a smooth, uninterrupted surface is essential. This is the most popular mounting style for purpose-built ball tables in manufacturing and logistics.
Considerations
Requires a precision-drilled hole to achieve the correct interference fit. If the hole is too large, the unit will not be held securely. If too small, the unit may be difficult to install or could damage the housing. Always follow the manufacturer’s recommended hole size tolerances.
Clamped Mounting
Clamped ball transfer units are secured using an external clamp or bracket arrangement that grips the housing from outside.
Advantages
• No drilling or threading of the mounting surface required
• Easy to reposition or remove without modifying the surface
• Suitable for temporary installations or test setups
Best For: Applications where the mounting surface cannot be drilled or threaded (such as structural steelwork or rented facilities), temporary or prototype installations, and situations where BTUs need to be repositioned frequently.
Considerations
Clamped mounting is generally less secure than bolted or press-fit alternatives and may not be suitable for high-vibration or heavy-load applications.
Base Fixing
Base-fixed ball transfer units are mounted from underneath the surface. The housing passes through a hole in the surface from below and is secured with a fastener or retaining mechanism underneath.
Advantages
• The cleanest possible top surface — no fixings visible from above
• Secure mounting with no components that could snag or interfere with items being moved
• Provides a premium, professional finish
Best For: High-specification ball transfer tables, cleanroom applications, and any installation where the top surface must be completely smooth and free from any protrusions or fixings.
Considerations
Requires access to the underside of the mounting surface for installation and maintenance.
Not practical for surfaces mounted directly onto solid structures without a gap underneath.
Choosing the Right Mounting Style
In most cases, the choice comes down to three practical questions:
Do you need a flush top surface? If yes, choose drop-in or base fixing.
Do you need easy removal for maintenance? If yes, flanged or threaded stem are the
most practical.
Can you drill or thread the mounting surface? If not, clamped mounting is your solution.
If you are unsure which mounting style is right for your application, the Alwayse Brief Builder tool can guide you to the right option based on your requirements, or contact the technical team directly for advice.
Frequently Asked Questions
What is the most popular ball transfer unit mounting style?
Drop-in (press-fit) mounting is the most widely used style for ball transfer tables and platforms, as it provides a completely flush surface finish with fast, simple installation.
Can I retrofit ball transfer units to an existing surface?
Yes. Flanged units are the easiest to retrofit, as they only require clearance holes for bolts. Threaded stem units can also be retrofitted if you can create threaded holes in the surface. Drop-in units require precision-drilled holes to the manufacturer’s specified tolerances.
What hole size do I need for a drop-in ball transfer unit?
The required hole size depends on the specific unit model and is specified by the manufacturer. Always refer to the product data sheet for the recommended hole diameter
and tolerance. Using the wrong hole size can result in a loose fit (unit falls out) or an overly tight fit (housing damage).
Can I adjust the height of a ball transfer unit?
Threaded stem (stud) mounted units offer built-in height adjustability — simply screw the unit further in or out to raise or lower the ball position. Other mounting styles have a fixed installed height.