Before you choose wheel diameter, tread material, or brake style, you must answer one question: How does the caster attach to your equipment? The mounting type determines whether installation is possible at all — and affects load capacity, stability, ease of replacement, and long-term retention.
Two common stem-type mounts — Bolt Hole (Centre Bolt / Single-Bolt Stem) and Grip Ring Stem (Friction Ring Stem) — are often confused. They look similar at a glance but attach differently and suit different applications. This guide explains the differences, pros/cons, sizing, and how to choose — following the same application-engineering standards used by China Zhongshan FFIBU Casters Co., Ltd when specifying FFIBU caster series.
A bolt-hole caster has a single plain hole through the centre of the swivel head (typically Ø 10.5 mm or 13 mm to accept an M10 or M12 bolt). There is no threaded stem and no grip ring. The caster is secured by passing a machine bolt up through a hole in the equipment base or tubular frame, through the caster's centre hole, and fastening with a lock nut + washer on top (or underneath, depending on access).
Some light-duty furniture casters use this same principle with a smooth stem + washer + nut, but the defining feature is the central through-hole in the swivel section itself.
Hole diameter: 10.5 mm (for M10 bolt) or 13 mm (for M12 bolt) — metric; 13/32" or 1/2" — imperial
Commonly paired with: light-duty or medium-duty swivel yokes on furniture, catering trolleys, display stands
Load range: generally light-duty (< 80–120 kg/caster)
Drill a matching hole in the equipment base/frame.
Insert bolt from accessible side ? through equipment ? through caster centre hole.
Secure with lock nut + flat washer; tighten to snug (do not overtighten and bind the swivel race).
? Simple, low-profile — no protruding stem below mounting surface
? Can be through-bolted for positive retention (nut can be Loctited)
? Easy to replace — unbolt, swap, re-bolt
? Works on thin plate or wood with backing washer to prevent pull-through
?? Requires drilled hole with backside access (or a tapped hole if using a stud)
?? Single-point fixing — lower resistance to racking/twisting vs. 4-bolt top plate
?? Not suitable for very heavy loads or high side-thrust applications
A grip ring stem caster has a round stem with a circumferential groove near the top, into which a split steel or brass ring (the "grip ring") is installed. The stem is pressed into a matching-size hole or socket molded or drilled into the equipment leg. As the stem enters, the ring compresses; once fully seated, the ring expands into a matching recess or simply provides friction against the hole wall, locking the caster in place.
Common office-chair / institutional size: 7/16" (?11 mm) diameter × 7/8"–1" long with grip ring. Industrial versions may use 1/2", 5/8" or M12 stems.
Stem Ø: 7/16" (11 mm), 1/2" (12.7 mm), 5/8" (16 mm), M10, M12
Stem length: typically 25–38 mm (1"–1.5")
Load range: light to medium duty (office chairs, retail displays, light instrument carts)
Align caster stem with socket/hole in equipment leg.
Tap firmly with a rubber mallet until the grip ring seats fully.
No bolts, nuts, or tools required on the equipment side.
Removal: Pull or pry out with moderate force; some sockets have a small release notch.
? Fastest installation — push-fit, no hardware needed
? Ideal for tubular legs and molded sockets (office chairs, shop fixtures)
? Low profile — no bolt heads or plates visible
? Quick field replacement (pull old, tap in new)
?? Retention is friction-based — can loosen over time, especially on rough floors or with side loads
?? Requires precisely sized receiving hole (typically +0.1 to +0.3 mm over stem Ø) — oversize hole = sloppy/won't retain
?? Lower load capacity than plate-mount or threaded-stem casters
?? Not suitable for high-impact or heavy-duty industrial carts
Feature | Bolt Hole (Centre Bolt) | Grip Ring Stem |
|---|---|---|
Attachment Method | Machine bolt through centre hole, secured w/ nut | Stem w/ friction ring pressed into sized socket/hole |
Tools Required | Wrench / socket set | Rubber mallet (to tap in) |
Backside Access Needed? | Yes (to tighten nut) or pre-tapped hole | No |
Retention Security | High (mechanical fastener, can use threadlocker) | Medium (friction fit; can loosen over time) |
Load Suitability | Light–Medium (depending on yoke & wheel) | Light–Medium (typically lower than bolt-hole equivalent) |
Best For | Furniture, light trolleys w/ drilled base, wood/metal tops | Office chairs, tubular-leg carts, molded-plastic equipment legs |
Replacement Ease | Unbolt / re-bolt | Pull out / tap in |
Typical Failure Mode | Bolt loosens (use lock washer/nyloc) | Stem works loose in oversize hole; ring fatigues |
Measure the centre hole diameter of the existing caster (common: 10.5 mm for M10, 13 mm for M12).
Confirm you have a hole in the equipment matching bolt size and can access the back side (or use a threaded insert).
Check overall height — bolt-head + washer thickness must clear any obstruction above mounting surface.
Stem diameter: measure with calipers — most common = 7/16" (11 mm) or 1/2" (12.7 mm); metric M10 = 10 mm.
Stem length: from base of swivel to tip — must fully engage the socket.
Socket/hole inner diameter: should be 0.1–0.3 mm larger than stem Ø for proper grip-ring compression.
If the existing caster pulls out easily ? socket may be oversize ? consider threaded insert + threaded stem retrofit, or expanding adapter if tubular.
Choose Bolt Hole (Centre Bolt) if:
Your equipment has a flat base with a drilled/bolted hole or you can add one
You want positive mechanical retention (nut + lock washer)
The caster must support moderate loads on a light-duty trolley or workbench
You have backside access to tighten the bolt
? FFIBU light/medium-duty swivel casters with centre bolt hole are commonly used on catering trolleys, lab benches, and display stands.
Choose Grip Ring Stem if:
Equipment has tubular legs or molded sockets sized for a stem (e.g., office chair, retail display, light instrument cart)
Installation speed matters and no tools/hardware are desired on customer side
Loads are light and side thrust is minimal
You are replacing an existing grip-ring caster on furniture/office equipment
? FFIBU institutional-series grip-ring stem casters are specified for office seating, AV carts, and light retail fixtures.
Choose Something Else (Top Plate / Threaded Stem / Expanding Adapter) if:
Heavy loads ? use 4-bolt top plate (distributes load, most stable)
Need secure stem in tubular frame with no molded socket ? use expanding rubber adapter stem or threaded stem with insert
Require frequent removal in dirty environments ? threaded stem with nyloc nut may be preferable to grip ring
? Using a grip ring stem in an oversize hole — it will wobble and fall out. Verify socket ID.
? Overtightening the bolt on a bolt-hole caster — can preload and seize the swivel race. Tighten snug + lock washer only.
? Assuming all "stem casters" are interchangeable — grip ring, threaded stem, and expanding adapter stems are not cross-compatible.
? Retrofitting a grip ring caster onto a frame that originally had a top plate — the frame may not have local stiffness to resist stem cantilever loads; reinforce if needed.
China Zhongshan FFIBU Casters Co., Ltd manufactures both mounting types within the FFIBU product range:
Bolt-Hole Centre-Mount Series: light to medium duty, PU/TPR/rubber wheels Ø 50–100 mm, centre hole Ø 10.5 mm (M10) or 13 mm (M12), with or without total-lock brakes.
Grip Ring Stem Series: institutional and office-grade, stem Ø 7/16" (11 mm) / 1/2" (12.7 mm) / M10, wheel Ø 50–75 mm, TPR or soft PU non-marking tread.
Threaded Stem & Expanding Adapter options also available for tubular-frame applications requiring more secure retention than grip ring allows.
Full dimensional drawings indicate hole Ø, stem Ø/length, and recommended bolt specs — so you can verify compatibility before ordering.
Bolt hole and grip ring stem casters both serve light-to-medium duty mobility needs, but they are not interchangeable:
Bolt Hole = mechanically fastened through a single bolt — more secure, requires drilled hole + access.
Grip Ring Stem = friction-fit into a sized socket — fastest install, ideal for tubular/off-the-shelf furniture legs.
Matching the mount type to your equipment's existing (or planned) attachment point prevents installation headaches and ensures safe, stable operation. When in doubt, the technical team at China Zhongshan FFIBU Casters Co., Ltd can review photos or drawings of your mounting surface and recommend the correct FFIBU caster mount type and model.