3/8" Chainsaw Rim Sprocket 7 Tooth Small 7 Spline – LN18720
Professional quality 3/8" pitch 7-tooth chainsaw rim sprocket designed for chainsaws using a Small 7 Spline (SM7) clutch drum system.
Manufactured from tough, wear-resistant steel for durability, smooth chain operation and reliable power transfer from the chainsaw engine to the saw chain.
The floating rim sprocket design allows the saw chain to naturally align with the guide bar groove, helping provide smoother cutting and more even wear across the chain, guide bar and drive components.
This Small 7 Spline rim sprocket is physically different from the more common Standard 7 Spline rim. Always check the size of your existing rim sprocket before ordering.
PRODUCT DETAILS
✅3/8" Pitch Rim sprocket
✅7-Tooth Configuration
✅Small 7 Spline (SM7) Fitment
✅Hardened Wear-Resistant Steel
✅Exceptional reliability
✅Professional performance
✅Smoother cutting performance
✅Designed to Reduce Uneven Chain & Bar Wear
✅Easy Replacement Rim Design
✅Helps Maintain Correct Chain Alignment
✅Professional Forestry Grade Performance
OEM CROSS REFERENCE
• Oregon 18720
• GB GBA7S7
SMALL 7 SPLINE – IMPORTANT
This sprocket uses the Small 7 Spline (SM7) configuration.
It should not be confused with the Standard 7 Spline (SD7) 3/8" 7-tooth rim sprocket, commonly cross-referenced as Oregon 68210.
Although both sprockets are:
• 3/8" Pitch
• 7 Tooth
• 7 Spline
…the centre spline size is different, meaning they are not interchangeable.
If your existing rim is marked 18720 or SM7, this is the small spline version you require.
WHY USE A RIM SPROCKET?
A rim sprocket forms the connection between the chainsaw clutch drum and saw chain.
Unlike a fixed spur sprocket, the replaceable rim floats slightly on the clutch drum spline, allowing the chain to align naturally with the guide bar groove.
This design helps provide:
✅ Smoother Chain Operation
✅ Improved Chain Alignment
✅ More Even Sprocket Wear
✅ Reduced Saw Chain Wear
✅ Longer Guide Bar & Drive Component Life
The replaceable design also allows the rim sprocket itself to be changed without replacing the complete clutch drum, provided the existing drum remains serviceable.
WHEN SHOULD I REPLACE MY RIM SPROCKET?
The chainsaw rim sprocket is a wear component and should be inspected regularly.
As the sprocket wears, grooves can develop where the saw chain drive links contact the rim. Excessive wear can result in poor chain engagement, vibration and accelerated wear of both the chain and guide bar.
For best cutting performance, regularly inspect the rim sprocket when replacing your chainsaw chain and replace it when excessive wear is visible.
SMALL 7 SPLINE OR STANDARD 7 SPLINE?
This is particularly important when purchasing a replacement chainsaw sprocket.
Small 7 Spline (SM7)
Smaller centre spline – this product.
Standard 7 Spline (SD7)
Larger centre spline – a different rim sprocket.
Both versions are available in 3/8" pitch and 7-tooth configurations, so pitch and tooth count alone are not enough to determine correct fitment.
IMPORTANT FITMENT INFORMATION
Before ordering, compare this sprocket with your existing rim and confirm:
• Pitch – 3/8"
• Tooth Count – 7 Tooth
• Spline – Small 7 Spline (SM7)
• Cross Reference – Oregon 18720
If you're unsure which rim sprocket fits your chainsaw, contact Longer Chainsaws with your chainsaw make and model before ordering.