Easy
Less than 15 minutes
This is an OEM approved replacement part designed for use with chainsaws. The primary purpose of this part is to attach the chainsaw bar to the main unit. There are two of these mounting nuts used to secure bar. It is a metal hex flange nut and it is sold individually. You will need a wrench when working with this item.
Guide Bar Nut 5/16-18 678339003
OEM part for: Ryobi, Homelite, Ridgid
Part Number: 678339003
$4.99
In Stock
Ships within 1 business day 
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Compatibility
This Guide Bar Nut 5/16-18 will fit the following 48 machines. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Ryobi
Homelite
Ridgid
Show More Compatible ModelsThis item works with the following types of products:
- Chain Saw Parts
- Saw Parts
- Generator Parts
Customer Part Reviews ?
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Several parts ordered
Not the first time I ordered replacement parts from this company. As usual the parts arrived in time and the quality was great. They keep my old tools running.
Frank -
December 7, 2021
Verified Purchase
Worked as advertised
Happy with the fitment, works as advertised. I would buy here again.
Guest -
October 29, 2019
Verified Purchase
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Customer Repair Instructions ?
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part.
Bar was bent
Adam - March 16, 2017
👍 1 of 1 people found this instruction helpful
Tool Type
Chain Saw
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
, Combination Wrench
Removed the chain cover assembly
Reduced the tension on the blade and removed it and the bar
Replace the bar with the new one, installed the chain
Adjusted the chain tension
Attach the chain cover with the new nut
Reduced the tension on the blade and removed it and the bar
Replace the bar with the new one, installed the chain
Adjusted the chain tension
Attach the chain cover with the new nut
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Lost chain bar nuts.
Rex - March 18, 2018
Tool Type
Chain Saw
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
, The wrench included with the chain saw.
Parts Used
Put nuts on.
Tightened nuts.
Started saw.
Saw worked.
Tightened nuts.
Started saw.
Saw worked.
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Needed new guide bar nut
Jackie - December 6, 2017
Tool Type
Chain Saw
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
Socket set
Parts Used
Simply installed it
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Sprocket drum gear worn. Muffler gasket burnt.
larry - November 4, 2017
Tool Type
Chain Saw
Difficulty
Easy
Time
15-30 minutes
Tools Used
Screwdriver, Pliers
1. Removed the chain cover.
2. Removed the chain and the bar.
3. Removed the e-clip from the sprocket.
4. Removed the sprocket drum.
5. Installed the new sprocket drum.
2. Removed the chain and the bar.
3. Removed the e-clip from the sprocket.
4. Removed the sprocket drum.
5. Installed the new sprocket drum.
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Damaged guide bar plate, missing guide bar nut
Mike - September 24, 2016
Tool Type
Chain Saw
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
, Combination wrench for chainsaw
1. Removed existing guide bar nut 5/16-18
2. Removed guide bar cover
3. Installed guide bar plate
4. Installed guide bar cover
5. Fastened guide bar cover with guide bar nuts (2)
6. Adjusted guide bar tension with combination wrench
7. Tightened guide bar nuts with combination wrench
8. Started chainsaw
2. Removed guide bar cover
3. Installed guide bar plate
4. Installed guide bar cover
5. Fastened guide bar cover with guide bar nuts (2)
6. Adjusted guide bar tension with combination wrench
7. Tightened guide bar nuts with combination wrench
8. Started chainsaw
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Our product descriptions are a combination of data sourced directly from the manufacturers who made your product as well as content researched and curated by our content & customer service teams. This content is edited and reviewed internally before being made public to customers.
Our customer service team are at the ready daily to answer your part and product questions. We have a dedicated staff with decades of collective experience in helping customers just like you purchase parts to repair their products.
All our part reviews are solicited directly from other customers who have purchased this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
Based on data from past customer purchasing behaviors, these parts are most commonly purchased together along with the part you are viewing. These parts may be necessary or helpful to replace to complete your current repair.
All our installation videos are created and produced in collaboration with our in-house repair technician, Mark Sodja, who has helped millions of eReplacementParts customers over the last 13 years repair their products. Mark has years of experience in selling and repairing both commercial and residential products with a specialty in gas-powered equipment.
This data is collected from customers who submitted a repair instruction after replacing this exact part. Customers can rate how easy the repair was to complete and how long it took. We aggregate this data to provide a repair rating that allows customers to quickly determine the difficulty and time needed to perform their own repair.
