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Sharpening a Stihl "scratcher tooth" trimmer blade?


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#1 zuren OFFLINE  

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Posted June 07, 2018 - 11:05 AM

I have a Stihl FS90R that I use for everything around my 5 acres, including cutting down buckthorn saplings.  The blade has become dull and despite the guidance from Stihl that it needs to be professionally sharpened, I'm trying to figure out if I can sharpen it myself.  Has anyone sharpened a blade like this?

 

Thanks!

 

https://www.stihlusa...ircularscratch/

circularscratch.png?preset=Product.Produ


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#2 Billy M ONLINE  

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Posted June 07, 2018 - 11:41 AM

I have sharpened them with a Dremel & #420 cut-offf wheel with success.  You really just need to square up the tips & make them sharp.  That's where the magic happens.


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#3 firedudetl1 OFFLINE  

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Posted June 07, 2018 - 11:55 AM

my 2 cents.. I'd get a 1/2 flat/1/2 round file or a triangle file that fits in without hitting the back tooth, make a jig to hold the blade (1/2 round flat stock screwed together to hold the blade in place, then put in a bench vise) file the teeth to match the existing edge and that's it - might take a while but once you're used to it, shouldn't be too bad


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#4 chieffan OFFLINE  

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Posted June 07, 2018 - 12:37 PM

The problem is keeping the teeth at the right bevel  which is very hard to do by hand.  An experienced sharpener can do it but if you have not filed a circular saw blade before it is different.  Might get by doing it a couple time but I have seen a ton of different blades that people tried to sharpen them selves and did nothing but screw them up.  I sharpen saw blades as a hobby more than a business and have the machines to do it right.  Don't get rich at $.15 a tooth which includes clean up.  Especially when diamond wheels are over $100 each.

 

If your going to try it anyway, makes sure each tooth is filed at the same angle, the same number of strokes with the same amount of pressure, very light.


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#5 chieffan OFFLINE  

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Posted June 07, 2018 - 03:20 PM

I have sharpened them with a Dremel & #420 cut-offf wheel with success.  You really just need to square up the tips & make them sharp.  That's where the magic happens.

 

The "tips" are not square to start with and messing with them the way you mentioned is Ok if want to mess up a saw blade.



#6 4getgto ONLINE  

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Posted June 07, 2018 - 04:39 PM

At about $20 for a new one hard to believe you can have one sharpened for less. Try it yourself. Nothing to lose.
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#7 LilysDad ONLINE  

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Posted June 07, 2018 - 04:50 PM

After a few hand sharpenings, it may become out of balance.


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#8 EricFromPa ONLINE  

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Posted June 07, 2018 - 05:50 PM

Got a vice and a thin cut off wheel on a grinder? Or a good quality hard file like a nicholson single cut draw file. You can get them razor sharp with very little work with a Good file.

 

 

I have a nasty looking carbide tipped circular saw blade on my big old Homelite whacker. The carbide tipped blades work awesome but beware of the tips flying off if you hit something hard like a rock.  

 

Blades like these work really good if you modify your blade adapter so they fit tight. You can get smaller or larger ones with the same hole size.

 

https://www.walmart....a1d&athena=true  

 

 

I bet this one would rip up some buckthorn or anything else in it's way.

 

https://www.walmart....c66&athena=true


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#9 chieffan OFFLINE  

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Posted June 07, 2018 - 06:23 PM

After a few hand sharpenings, it may become out of balance.

 

And out of round.  You'd be surprised how many low $ blades are not true round and the spacing of the teeth is not consistent.  That's why they vibrate when you use them.  Hard on bearing too.  More to sharpening a blade than taking off some metal.


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#10 secondtry ONLINE  

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Posted June 07, 2018 - 10:15 PM

  Same principal as any other blade, consistent height angle and set and you will be fine. To get every thing perfect requires precision equipment. Hand sharpening can be an improvement but not likley to be perfect. Don   


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#11 firedudetl1 OFFLINE  

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Posted June 08, 2018 - 06:00 AM

looks like about a 50 tooth blade - if it can be sharpened for $0.15/tooth, I can't see how doing it yourself is more cost & time  effective than spending $7.50 at a local shop that you could stop at when driving "around"...


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#12 TAHOE OFFLINE  

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Posted June 08, 2018 - 07:01 AM

install a large cutoff disc in a table saw, set the table at the tooth angle and go at it, saw a tutorial on youtube for sharpening regular circular saw blades that way


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#13 chieffan OFFLINE  

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Posted June 08, 2018 - 07:04 AM

looks like about a 50 tooth blade - if it can be sharpened for $0.15/tooth, I can't see how doing it yourself is more cost & time  effective than spending $7.50 at a local shop that you could stop at when driving "around"...

 

The 4.15 a tooth is what I charge.  Have no idea what someone out that way would charge.  When you do it your self what about getting the pitch off the blade before you file it?  If you don't your file will get clogged up with the pitch and won't cut right, then you have a messed up blade and a file that won't cut.  Double loss.  Now you can go buy a new blade and a new file.  But I will give you a tip.  Water with Mean Green  - overnight soaking - clean with a brass brush.


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#14 SupplySergeant ONLINE  

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Posted June 08, 2018 - 07:21 AM

https://www.harborfr...ener-96687.html

 

Gets pretty good reviews. I'm watching this since I have the same weed whacker and blade!


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#15 Billy M ONLINE  

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Posted June 08, 2018 - 08:35 AM

The "tips" are not square to start with and messing with them the way you mentioned is Ok if want to mess up a saw blade.

Sure the tips are square...round tips don't cut very well!   :D   I was referring to the point of the blade. 

 

Sharpening a blade to cut brush isn't rocket science.  I cleared a couple acre lot in KY with this blade and have sharpened it plenty of times with my Dremel.  Trust me...hit one rock and the blade is toast, and there is a lot of rock in KY!  I personally wouldn't get a brush blade professionally sharpened.  I'm just not that concerned about nice, true, square cuts on a stick.  A circular saw blade that I want a nice clean cut from...I would definitely get that professionally sharpened.  I'm no sharpening pro by any means.


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