Oregon Mulch Blade 3 or 4mm

[Capscrew]

I am planning on getting an Oregon 3 point mulching blade for dealing with a large area of strong Brambles and some Blackthorn suckers 1/2" to 1" dia stems.

 

Which blade should I get, 3mm or 4mm?

 

My current Brushcutters are a Stihl FS120 and a SGS 52cc.

 

Thanks for any advice you can give me.

[Grassyass]

We are currently using the 3 point mulch blade(4mm) and yesterday broke the clutch housing on a stihl fs460 ,we have  used lots of stihl blades over the years and never had this problem , you can see the strimmer shaft flex if you hit a solid object with the Oregon blade , 

Edited June 9, 2022 by Grassyass

[openspaceman]

7 hours ago, Capscrew said:

I am planning on getting an Oregon 3 point mulching blade for dealing with a large area of strong Brambles and some Blackthorn suckers 1/2" to 1" dia stems.

 

Which blade should I get, 3mm or 4mm?

 

My current Brushcutters are a Stihl FS120 and a SGS 52cc.

 

Thanks for any advice you can give me.

For the 1"  blackthorn it'll be a bit of a jolt with a mulching blade. A saw blade will be quicker but you don't get multiple cuts to mulch it.

 

I have a 4mm 2 bladed mulcher on my 50cc brushcutter and wouldn't risk anything thinner, it will easily cope with any brambles. What benefit does a 3 bladed mulcher give?

 

  The guys used to wear out these stihl two bladed mulching blades but I think a lot of that was down to them not using the cup underneath to keep the vertical bits of the blade from constantly hitting the ground.

[ChrisNewport]

Ive a 4mm three armed mulcher on a Stihl FS400, it batters most things put in front of it but i wouldnt attempt to knock down anything like 1 inch Blackthorn with it. I dont use the mounting cup as i like to skim the blade across the ground so everything is cut at ground level. It does wear the cutter down but a quick sharpen with the angle grinder every half hour keeps it sharp.

[openspaceman]

2 hours ago, Grassyass said:

We are currently using the 3 point mulch blade(4mm) and yesterday broke the clutch housing on a stihl fs460 ,we have  used lots of stihl blades over the years and never had this problem , you can see the strimmer shaft flex if you hit a solid object with the Oregon blade , 

Oh dear, my memory is a bit dim but there's a circlip retaining the shaft to that housing that is very awkward to get at.

[Grassyass]

Yes your right I saw the circlip on the parts diagram ,

[Stere]

Quote

Ive a 4mm three armed mulcher on a Stihl FS400, it batters most things put in front of it but i wouldnt attempt to knock down anything like 1 inch Blackthorn with it.

 

Yes   better off  using it with a saw tooth blade for the  1 inch blackthorn etc

 

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They work  well don't but mulch brambles though.... so best to have both blades

[Lanust]

Stihl only recommend their 2 point, 270mm shredder blades for their Clearing Saws of at least 1.9bhp or more, and their 320mm shredder blade only for the FS5xx series. The SGS GPS520 is 1.6hp. The FS120 is 1.8bhp and not intended/engineered to take the Stihl shredder blades.

 

The Oregon 3 point blade is 300mm and over diameter for all Stihl clearing saws except the FS5xx series machines. Stihl don't do a 3 point blade with good reason, they are heavier and have more inertia that has the potential to lead to overloaded drive train components as unfortunately demonstrated by Grassyass - "you can see the strimmer shaft flex if you hit a solid object with the Oregon blade" – enough said.

 

The fact that Oregon make those 3 point blades to fit everything doesn't make it a good idea to use them without considering the potential overload issues. They don't have to pick up the bill for worn/broken drive train components on brushcutters/clearing saws.

 

There is also an issue with the 20mm alloy spacer ring disengaging from the Stihl Clearing Saw blade drive flange arbor while in use allowing the blade to be knocked off centre.

 

Cheers.

 

[Capscrew]

Thanks everyone, you have given me plenty to think about, definitely going to get a saw blade for the Blackthorn though.

[Guest Gimlet]

I mulched literally thousands of self-seeded saplings with a 4 mm Oregon tri-point blade on 9 hectares of chalk downland that was under a restoration stewardship programme. They were mostly hawthorn and hazel with some oak. I used a 45cc Kawasaki badged Stiga brushcutter (crap, but that's another story) and I can tell beyond doubt that 1" is too thick.  If the drive train survives it you risk smashing the blade guard (as I did) with heavy lumps of debris. I stuck to about half inch stems and then you need to sweep them away in a series of passes from the top down. Trying to go straight in at the base could kill your drive shaft. Hazel I could get away taking a bit thicker because it splits and shatters readily but hawthorn was too dense. I would think blackthorn will be too.

 

Also it won't mulch the thick woody base of the stems that well and you end up with an awful lot of splintery shrapnel showered all over the place. But a saw blade will sing through a 2" stem with no effort at all. You have to go round and pick up the brash afterwards but it's easy enough to do with a muck fork and there's no mess left behind. I use a saw blade when I'm hedgelaying to clear blackthorn and bullace suckers that have advanced out into the field. I tried using the mulching blade but kept having to stop when I encountered something too big, plus it's not so easy to cut them tight to the ground so I was ending up with little stumps everywhere that I kept tripping over. the saw blade was far less stressful on the machine, much faster and neater. 

 

My 45cc engine could handle the blade weight no problem (I used it on a 25 cc Echo previously and it killed the bottom end). There's considerable inertia to overcome to get a 4 mm blade spinning so the engine won't rev up as quickly as usual, but provided you're not having to hold the throttle flat out, it will handle it and the secret is to get it up to speed and keep it at that speed constantly. The three pointer makes very rapid work of shredding bramble. The way to do it is to pat the blade down on the top of the thicket rather than sweeping it side to side. the patting down technique is much easier to do on a machine with a D handle rather than cow horn bars, if you've got one that's powerful enough. The three pointer will reduce the heaviest bramble to a fine mulch which is great if you plan to spray off the new growth with Grazon or something similar.  

Be careful when sharpening to take the same amount off each tip so the blade stays balanced. If it's badly out of balance and sets up a lot of vibration that can damage your drive train as well. 

Edited June 17, 2022 by Gimlet