Hook Angle

[Boon]

I've been reading about progressive raker angles & suppose it is one of those things you don't quiet get until it is put into practice, so got me a Tool Master digital angle finder from Hare & Forbes coming next week and will go about setting raker angles.

Have read the threads on hook and still don't quiet get what is going on. What I mean is on the grinder the angle may be set at 50 degrees but using a file then resets the hook angle according to the size file used.

Next year I have some stringy bark, blue gum & turpentine to mill up all have been down for some time - no doubt will be hard as & am hoping to get the most from my chains. I will be using Stihl semi chisel, rapid micro 3/8 full comp & top plate angle of 15 degrees, Bobl mentions a zero degree top plant angle can go negative & hook angle is adequate so long as the mill self feeds. I have been using 15 degrees as I don't always cut hardwood and feel that angle still gives bite into most woods.

Reading the threads there was discussion what individually works for the user and there is a varied amount of hardness in the woods. My gut feeling is softer woods can tolerate angles that are set for hard woods but not the other way around.

Until now I have been trying to replicate angle of new chain from the box as it cuts the best when first used but my chains are starting to wear down and the cutting life on a clean log is noticeably decreasing.

Finding the angle that cruises through the hard woods still seems a mystery, the last threads I can find on hook were posted in 2011. Since that time has anyone come up with system for hook like Bobl's progressive raker angles that works?? mtngun has done some interesting experiments but the wood was soft.

 

[BobL]

. . . . . . Bobl mentions a zero degree top plant angle can go negative & hook angle is adequate so long as the mill self feeds. I have been using 15 degrees as I don't always cut hardwood and feel that angle still gives bite into most woods..

Bite into the wood is primarily controlled by hook. The top plate filing angle controls the sideways bite into the wood. In cross cutting the ends of the torn wood fibres hang inside the cut so higher angles are needed to create a slightly wider kerf to help clear sawdust. When milling there are fewer torn fibres hanging inside the kerf so slower angles can be used.

Reading the threads there was discussion what individually works for the user and there is a varied amount of hardness in the woods. My gut feeling is softer woods can tolerate angles that are set for hard woods but not the other way around.

correct

Until now I have been trying to replicate angle of new chain from the box as it cuts the best when first used but my chains are starting to wear down and the cutting life on a clean log is noticeably decreasing.

thats not a hook angle issue but a raker depth issue. To find out of that is the case just take one of those chains (sharpened according to your current method) and do enough enough cuts to establish how poorly it is cutting in your mind. Then swipe the rakers 5 times each and try again. keep doing this until it feels like a new chain. If you go too far the chain will start to generate more vibe and don't forget that the chance of kickback increases.

Finding the angle that cruises through the hard woods still seems a mystery,

err . . . . . I've never found any angles that "cruises" through Aussie hardwoods

the last threads I can find on hook were posted in 2011. Since that time has anyone come up with system for hook like Bobl's progressive raker angles that works?? mtngun has done some interesting experiments but the wood was soft.

Hook and raker angle are only loosely related. While both will contribute to the amount of "bite into the wood" that a cutter will make and more hook means more initial cutter bite but the ultimate depth that a cutter rocks its way into the wood is determined ultimately by the raker depth.

1) High hook angle and shallow raker setting = makes a lot of dust and the chain goes blunt quickly
2) Low hook angle and shallow raker setting = even finer dust, no amount of touching up the cutter seems to make any difference
3) Low hook angle and deep raker setting = more chain vibe, should male more chips, cutter should not go blunt as quickly
4) High hook angle and deep raker setting = aggressive grabby cutters placing greater load on the saw, makes more chips, will go blunt quicker

The trick is to find the sweet spot somewhere between the above settings

 

[Jim Timber]

Are you starting with milling chain?

 

[scheffa]

Bobl can you please explain hook angle to me. I mill quite a bit of hardwood and I'm happy with my sharpening, however having never had someone explain it to me well I could be missing out, especially running a 60" bar through yellow box, every bit counts

 

[Boon]

err . . . . . I've never found any angles that "cruises" through Aussie hardwoods

Thanks Bob........understand how that could be interpreted.What I mean is replicating the out of box new chain cutting speed which in comparison to the current cutting speed 'cruises'

1) High hook angle and shallow raker setting = makes a lot of dust and the chain goes blunt quickly
2) Low hook angle and shallow raker setting = even finer dust, no amount of touching up the cutter seems to make any difference
3) Low hook angle and deep raker setting = more chain vibe, should male more chips, cutter should not go blunt as quickly
4) High hook angle and deep raker setting = aggressive grabby cutters placing greater load on the saw, makes more chips, will go blunt quicker

The trick is to find the sweet spot somewhere between the above settings

ATM think I'm at deep raker setting and high hook angle on my cheap chain grinder I am sitting on the 75 degree mark to the right of 90 degrees or 65 degree mark to the left of 50 degrees. Will find out the true degrees when the angle finder arrives.

Bob would you say the hook angle on straight out of the box chain is correct/best or another angle ??

 

[Boon]

Are you starting with milling chain?

What do you mean by milling chain? skip tooth ripping? No - am starting with standard semi chisel chain and slowly grinding to 15 degrees top plate angle

Why?

 

[BobL]

ATM think I'm at deep raker setting and high hook angle on my cheap chain grinder I am sitting on the 75 degree mark to the right of 90 degrees or 65 degree mark to the left of 50 degrees. Will find out the true degrees when the angle finder arrives.

The raker angle is not something a sharpener can set, and an angle finder won't easily measure the hook angle.

So then Bob would you say the hook angle on straight out of the box chain is correct/best or another angle ??

Any angles that works for your circumstances are the best angles.
I don't get too hung up about hook angles so I haven't compared chain out of the box angles with my hook angles as I don't even know what mine are.
My concern is much more with the raker angle because small changes in this angle make such a big difference to performance

I file by hand using an Oregon file guide and use different size files in different size file holders to change the hook.
A smaller file in a larger size file holder produces more hook and VV.

By trial and error I found a 13/64 file in a 7/32 file holder (haven't found a 13/64 file holder) works for me in terms of reasonable chain speed and how often I need to sharpen in the sort of wood that I cut (my standard wood is green spotted gum)

If I cutting up something harder than green spotty I might use a 13/64 file in a 3/16 file holder, this decreases the hook, it does not self feed but chain does not go blunt as quickly.
For something softer I don't mess with the hook but give the rakers an extra swipe.

What I can tell you is that the raker angles for chain straight out of the box are slightly on the shallow side for what I like to do. These are set at these angles primarily for safety i.e. minimise kickback which is a non-issue in milling. To maintain this angle the raker depth should be 1/10th of the gullet width. So when a 3/8 chain is new the raker depth is 0.025" and the gullet is typically 0.25" This works out to a raker angle of 5.7º whereas I like to start at around 6.5º. On softer wood I will use 7 - 8º.

As the cutter wears and the gullet opens up the raker has to be dropped much more than 0.025" to maintain these angles. When the gullet is around 0.5" a 7 angle requires a raker depth of 0.060" - This frightens some folks and newbies would need to be careful using this chain for bucking but provided the hook is reasonable it will cut easily as good as chain out of the box.

Now when do we start talking about the shape of the raker?

 

[Boon]

By trial and error I found a 13/64 file in a 7/32 file holder (haven't found a 13/64 file holder) works for me in terms of reasonable chain speed and how often I need to sharpen in the sort of wood that I cut (my standard wood is green spotted gum)

If I cutting up something harder than green spotty I might use a 13/64 file in a 3/16 file holder, this decreases the hook, it does not self feed but chain does not go blunt as quickly.
For something softer I don't mess with the hook but give the rakers an extra swipe.

yes 13/64 in a 3/16 file holder, have this written on a post it note in front of me after reading about you mentioning this in a previous thread and double checked this morning what I was using.....same but probably due to lack of experience filing hundreds of teeth in one sitting am lazy and prefer to change chains but have been thinking to start filing instead of lick grinding at the end of the job.

Now when do we start talking about the shape of the raker?

I'm listening

 

[betterbuilt]

I started to reply when you first posted but figured others could help you better. I messed around with hook, but ended up over thinking it. So now I basically do what Bobl says and change the holder or the file. After I've set the rakers with the DAF. I use one of these most of the time in the field. . The little raker file on it helps me to know when to touch up the rakers again. I run between 6 degrees and 9 degrees on the DAF. I've found the log angle helps also. I shoot for 12-20 degrees for self milling. If there enough log angle and the chain is sharp, a little weight on the mill keeps it going. I hope this helps. I'm not the best at describing things.

 

[Boon]

I started to reply when you first posted but figured others could help you better. I messed around with hook, but ended up over thinking it. So now I basically do what Bobl says and change the holder or the file. After I've set the rakers with the DAF. I use one of these most of the time in the field. View attachment 385220 . The little raker file on it helps me to know when to touch up the rakers again. I run between 6 degrees and 9 degrees on the DAF. I've found the log angle helps also. I shoot for 12-20 degrees for self milling. If there enough log angle and the chain is sharp, a little weight on the mill keeps it going. I hope this helps. I'm not the best at describing things. View attachment 385393

Thanks you have described enough. Can you tell me what brand the file set up is?

 

[betterbuilt]

The picture Is Pferd but I also have a husqvarna that's exactly the same.

 

[Boon]

A friend called and wanted some timbers cut from a Blue Gum dropped a year ago. It is was my first chance to give the new raker angles and and file/holder combinations a go. I had spend 3 days over Christmas setting and sharpening my chains & was beginning to wonder if all that effort was worth the time. So yesterday proved it was all worth the effort, although only a few cuts were done, what was cut went beautifully, chips came out, the mill went at a steady pace, the 13/64 file in a 3/16 file holder did its job as BobL said and the saw had no problems with those angles.



Then mill rails would not fit on the log in parts as it dropped away and decorative timber was sought rather than structural so we build on top of the log



end of the day we got some 125 x 200, 200 x 200, 40 x 200 & 230 x 200's



love those raker/file settings & happy as a pig in IT !

 

[BobL]

Looking good.