Thread: Rakers

Originally Posted by MAPLEMAN

Bought 2 new skip tooth chains(Oregon 27rx) the other day and they are both leaving a very average cutting profile,eg,corrugated..one was sharpened at 10*,the other at 15*,the tops of the rakers are shiny,and to me appear too high,however the bloke at the chainsaw shop where they were sharpened,said to me that the rakers should never be touched ...will high rakers cause the cut to be corrugated?..something is not right ,help muchly appreciated..MM

Raker depths are not a fixed quantity and depend on things like saw power, chain speed, cutting with and wood hardness.
As a guide, for aussie hardwoods they should be ~10% of the gullet width but in softwoods it would not be unusual to use 15-17% of gullet width..
e.g. new 3/8 chain has a gullet width of ~0.25" so the raker depth should be 0.025"
Some of my old chains where the cutter has just about gone have gullets of around 0.45" and raker depths are thus 0.045"

Corrugations (or Washboard) have very little to do with rakers.
In the picture below two cuts done one after the other - the cut on the left was done first then the cut on the right - same log, same saw, same chain but with a two file strokes per cutter touchup in between the two cuts.
The main difference between the two cuts was the WIDTH of the cut. The LHS one being ~400mm and the RHS one being ~500 mm

Corrugations appear to be caused by some sort of a synchronisation between the forward cutting speed and the sideways chain speed where a cutting cutter enters and grabs wood just as the bar moves on.
I rarely see this effect on wide cuts and I see it more often with skip chain in softer, esp. sap, wood.

MM, rakers too low will give aggressive finish, not too high. But top plate angle of 15 deg will give more aggressive finish as compared to 10 deg. Having said that 15 deg isn't a 'bad' finish. You may find hook angle is extreme, that combined with a nice 10 deg top plate angle will give aggressive finish

Originally Posted by Sigidi

MM, rakers too low will give aggressive finish, not too high. But top plate angle of 15 deg will give more aggressive finish as compared to 10 deg. Having said that 15 deg isn't a 'bad' finish. You may find hook angle is extreme, that combined with a nice 10 deg top plate angle will give aggressive finish

Cheers Alan...the blokes at the shop were sharpening one chain at 35* when i went to collect them,they were astounded that i wanted them done at 10*..i checked rakers out again,i think they could well be too low,this would explain the corrugation,as you mentioned..will sharpen chains myself today and report if there is an improvement in cutting profile..should have bought them directly from Lucas ..MM

Originally Posted by BobL

Raker depths are not a fixed quantity and depend on things like saw power, chain speed, cutting with and wood hardness.
As a guide, for aussie hardwoods they should be ~10% of the gullet width but in softwoods it would not be unusual to use 15-17% of gullet width..
e.g. new 3/8 chain has a gullet width of ~0.25" so the raker depth should be 0.025"
Some of my old chains where the cutter has just about gone have gullets of around 0.45" and raker depths are thus 0.045"

Corrugations (or Washboard) have very little to do with rakers.
In the picture below two cuts done one after the other - the cut on the left was done first then the cut on the right - same log, same saw, same chain but with a two file strokes per cutter touchup in between the two cuts.
The main difference between the two cuts was the WIDTH of the cut. The LHS one being ~400mm and the RHS one being ~500 mm

Corrugations appear to be caused by some sort of a synchronisation between the forward cutting speed and the sideways chain speed where a cutting cutter enters and grabs wood just as the bar moves on.
I rarely see this effect on wide cuts and I see it more often with skip chain in softer, esp. sap, wood.

Cheers Bob for all that info..MM

Spoke to the lucas team this morning,and they were very helpful in trying to sort out my plight...will attack the milling again tomorrow and see how things pan out..MM

MM, have you got yourself a file o plate? Quick easy and best thing for working the rakers back, even if your chain is cutting bad it will bring it back.

Originally Posted by Sigidi

MM, have you got yourself a file o plate? Quick easy and best thing for working the rakers back, even if your chain is cutting bad it will bring it back.

I think i have one somewhere buried ..if not,will get lucas to send me one..MM

Originally Posted by Sigidi

MM, have you got yourself a file o plate? Quick easy and best thing for working the rakers back, even if your chain is cutting bad it will bring it back.

I don't have one but based on the U-Tube videos, I took it only works on standard chains, as it uses the following tooth to line it up. For skip chains it wouldn't be of any use, or am I not understanding how it works?

Originally Posted by dai sensei

I don't have one but based on the U-Tube videos, I took it only works on standard chains, as it uses the following tooth to line it up. For skip chains it wouldn't be of any use, or am I not understanding how it works?

It works on skip chains OK - it doesn't actually need the following cutter to align itself as it hooks itself onto the raker and the other end can just ride on the chain.

I've only used a fileoplate a few times and find that they do not lower the rakers anywhere near enough, especially for softer woods.

tehy do when you modify them bob, just gota take a bit more out where the plate sits on teh chain. easily done with a grinder

They have two settings, one much higher than the other, I figure the one which lowers the rakes the least, hole 'A' is used for hardwood and the one that lowers rakers the most, hole 'B' would be for softwood.

When/if you get one make sure you get one for 404 chain

Is this what we are talking about?

C65957 Carlton File O Plate 404 Pitch 063 080 | eBay

Originally Posted by dai sensei

Is this what we are talking about?

C65957 Carlton File O Plate 404 Pitch 063 080 | eBay

Yep - that looks like one of the older ones.

I took mine out and had a play with it today. As Carl says they can be made more aggressive with an angle grinder but looking at the geometry and operation of the FOP it would need to be constantly modified during the life of a chain to maintain a constant raker angle. But this would then mean that they would then set the rakers too aggressively for a new chain.

When doing the rakers with an FOP, the way I see it is that there are two contact points, the top of the cutter, and the other end is the slot that sits on top of the chain ties. As the cutter wears the contact point on top of the cutter drops which exposes more raker so that it can be filed off. However the distance between the raker and the top of the cutter increases and makes then raker angle shallower which is undesirable since it does not allow the cutter to grab the wood in the same way it did when it was new.

In the diagram blow the blue line shows the angle at which an FOP would sit on a new cutter/raker.
The green line shows the angle the FOP will sit on a well used cutter, showing a significant amount of raker will be removed BUT the green line is not the same angle as the blue line.
To maintain the same raker angle between new and well used cutters, what is really needed is for the FOP to sit at the orange line i.e. Orange and blue are at the same angle.
The orange line removes significantly more raker than the green line so the chain will keep cutting as good as when it was new.

When ever I show this method to experienced chainsaw operators all over the world they initially think it is way too extreme (yep there is stuff all raker left on an old cutter) but everyone I know that tries this method never goes back to their old ways because it allows them to keep using their chains cutting as good as when it new throughout the life a chain.


The Oregon raker guides are a bit of a klutz but I noticed a couple of years ago that they do at least come in a range of raker depth settings, with increments of 0.005" i.e. 0.025', 0.030, 0.035, 0.040, 0.045 etc.
This means you would need a set of these the raker tools but at least the rakers can be set to the nearest 0.005".
One way to do this would be to measure the gullet and then select the guide that is closest to 1/10th of the the gullet, e.g. if the gullet was between 0.38 and 0.42" thne select the 0.040" guide.

I went through all this back in 2009 on the Arborisite - it's a pity they lost all the pictures otherwise I would have just posted a link.

Are the rakers factory set when new? I did request the chain be sharpened,and rakers set, when i ordered the chains new,and when i picked them up,assumed they were..unfortunately,after 2 sharpens,they are still corrugating the surface ..MM