Suitable grease for hedge trimmer gears and brush cutter heads

[doobin]

You’ve got to keep pumping it into the petrol ones. It will get thrown off the gears during work, and then will just sit in the corners emulsifying. 
 

You won’t hurt it, any excess will just work out past the plastic seals onto the blades. Plenty does this when it gets warm too. 
 

Basically, gears like that should run in an oil bath but that makes the sealing too complicated so Stihl used grease. To prolong life you need to be regular on the greasing. 
 

[pleasant]

2 hours ago, doobin said:

You’ve got to keep pumping it into the petrol ones. It will get thrown off the gears during work, and then will just sit in the corners emulsifying. 
 

You won’t hurt it, any excess will just work out past the plastic seals onto the blades. Plenty does this when it gets warm too. 
 

Basically, gears like that should run in an oil bath but that makes the sealing too complicated so Stihl used grease. To prolong life you need to be regular on the greasing. 
 

 

 

No manufacturer recommends this at all. And in all my years of repairing machinery, neither have I.

 

This quote from a few years ago on here, sums it up quite nicely and is the correct approach:

 

GardenKit

• 
• Veteran Member
• • 5.2k
• Location: Devon

 

Posted February 18, 2013

Take the cover off any hedge trimmer gear case and you will find the grease stuck to the casing, but when its warm it will flow back to where its needed as long as there is enough of it. The casing should ideally be no more than half full.

Lithium EP grease is fine.

•  

• Quote

Independent Garden Machinery dealer and Aspen Service Centre in Devon

Edited December 6, 2022 by pleasant

[Kimosabi]

Completely agree with doobin those stihl hedge cutters need greased once a day, you can normally hear the gears starting to chatter late in the afternoon, pull the cover off at the end of the day and smear some grease around the gears it only takes 2 minutes 

[pleasant]

2 hours ago, doobin said:

You won’t hurt it, any excess will just work out past the plastic seals onto the blades. Plenty does this when it gets warm too. 

Excess grease being pushed out through the blade seals illustrates more grease is a waste of time and money- but with blown seals it will also allow debris to be dragged back into the gearbox, which is something you definitely don't want. It's a seal for a reason.....the name gives it away.

[doobin]

2 hours ago, pleasant said:

Excess grease being pushed out through the blade seals illustrates more grease is a waste of time and money- but with blown seals it will also allow debris to be dragged back into the gearbox, which is something you definitely don't want. It's a seal for a reason.....the name gives it away.

It’s not really a seal is it? That’s the point. It’s a bit of plastic. 
 

They really aren’t complicated machines, and I’ve seen enough failed due to lack of grease to know that they need greasing regularly. The point about grease melting is a valid one, however once grease has emulsified it will no longer melt and flow. 
 

Keep your greasing regular, keep the grease fresh and they will not give you any bother. 
 

You could also look at using a moly based grease as used on pins/bushes and breakers. Should leave a film of moly as a protectant even when the rest of the grease has retreated to the outer recesses.