Effect Of Profiling Rakers (Depth Gauges) On Bore-Cutting?

[SteveSr]

Hello,

Freshly sharpened semi-chisel chain and I took a little off the rakers but didn't bother to profile the leading edge like Stihl suggests.

I noticed that the chain limbed and cross cut well. However I noticed considerable vibration and bucking when bore cutting a 10" diameter piece of maple. I also noticed similar similar vibration and bucking when trying to slab (rip cut) the stump of the same maple tree.

So what is the likely cause of this vibration and roughness? Is it related to the non-profiled rakers or is there some other sharpening defect that I should look for and remedy?

 

[Justsaws]

When the cutting edge of the tooth bites into the wood it pulls the front of the chain up and presses the depth gauge into the wood until that action forces the cutting edge of the tooth out of the wood. If the leading edge of the depth gauge is not profiled at all and a large flat top surface and little rounded leading edge is present it supposedly causes increased vibration, drag and wear as it engages the wood differently than a nicely profiled one.

Also changing the angle that occurs between the top edge of the depth gauge and the leading edge of the top of the cutter has a significant influence on the vibrations that are caused by cutting action of the chain. This change in vibration will be made more extreme by a non profiled depth gauge. A large increase in angle can make the chain take a bigger bite and that bigger bite causes more vibration, especially in semi chisel and chipper profiles. The harder the cutter edge engages the wood the more it is pulled out of line both up and down and side to side.

New chains are fairly conservative in the overall working order, kind of sharp, relatively smooth and fairly tight. Start changing stuff around it could cut faster and not be as smooth, might be smoother and not as fast.

Semi chisel is rough as it is never really fast or smooth to begin with, so any big change will be noticeable, especially if the cutter angles are off between cutters and or the depth gauges are significantly different.

 

[Huskybill]

Bore cutting, making a horizontal cut straight into a log or timber right?

We were speed cutting at the local fair. I was new at it with a 2100. I had six slices with two bore cuts. I set the rakers between .040” to .050” for pine. I left the dual spikes on. The 404” chain actually pulled the bar into the wood I tried with everything I had to hold the saw back it pulled me in with it. The spikes went into the timber. I had to yank the saw out.

After seeing this I cut my rakers .030” to .035” the big power head with the shorter bars liked it. It would muscle thru anything. When my rakers are almost flush I make three passes with a flat file.

At one fair my 2100 did eight cuts in 17.5 seconds. The local fairs had speed cutting.
In washington, ct they had the timber sports but you had to be invited to perform there I wasn’t that good. But we had a few local loggers who competed.

 

[buzz sawyer]

When the cutting edge of the tooth bites into the wood it pulls the front of the chain up and presses the depth gauge into the wood until that action forces the cutting edge of the tooth out of the wood. If the leading edge of the depth gauge is not profiled at all and a large flat top surface and little rounded leading edge is present it supposedly causes increased vibration, drag and wear as it engages the wood differently than a nicely profiled one.

Also changing the angle that occurs between the top edge of the depth gauge and the leading edge of the top of the cutter has a significant influence on the vibrations that are caused by cutting action of the chain. This change in vibration will be made more extreme by a non profiled depth gauge. A large increase in angle can make the chain take a bigger bite and that bigger bite causes more vibration, especially in semi chisel and chipper profiles. The harder the cutter edge engages the wood the more it is pulled out of line both up and down and side to side.

New chains are fairly conservative in the overall working order, kind of sharp, relatively smooth and fairly tight. Start changing stuff around it could cut faster and not be as smooth, might be smoother and not as fast.

Semi chisel is rough as it is never really fast or smooth to begin with, so any big change will be noticeable, especially if the cutter angles are off between cutters and or the depth gauges are significantly different.

Thanks for using the correct term "depth gauges". It's also important to note the reason for "safety chain" - the extra bump ahead of the depth gauge decreases the potential for kick-back when cutting near or with the tip of the bar, as with bore-cutting.

 

[HarleyT]

We need some good german input on this......

 

[PogoInTheWoods]

​

If not so anal as to actually profile a depth gauge with a curved shape, at least file it at a downward angle toward the leading edge instead of just flat (parallel) with the bar.

 

[SteveSr]

Bore cutting, making a horizontal cut straight into a log or timber right?

Correct.

We were speed cutting at the local fair. I was new at it with a 2100. I had six slices with two bore cuts. I set the rakers between .040” to .050” for pine. I left the dual spikes on. The 404” chain actually pulled the bar into the wood I tried with everything I had to hold the saw back it pulled me in with it. The spikes went into the timber. I had to yank the saw out.

After seeing this I cut my rakers .030” to .035” the big power head with the shorter bars liked it. It would muscle thru anything. When my rakers are almost flush I make three passes with a flat file.

.040-.050 sounds really aggressive but maybe not for .404 chain. I think that the .325 .o63 that I am using Stihl recommends about .020-.025 using their depth gauge tool.

 

[SteveSr]

New chains are fairly conservative in the overall working order, kind of sharp, relatively smooth and fairly tight. Start changing stuff around it could cut faster and not be as smooth, might be smoother and not as fast.

Sounds somewhat like my experience. Duller and less aggressive chains seem to bore cut better. I have noticed that new chains do seem to bore cut well.

Semi chisel is rough as it is never really fast or smooth to begin with, so any big change will be noticeable, especially if the cutter angles are off between cutters and or the depth gauges are significantly different.

Looks like I need to go profile the rakers and inspect the rest of the chain. Unfortunately, my main test log is not maple but sweet gum. I may get a chance to cut some maple next weekend.

BTW, How does the species or hardness of the wood fit into this picture. Is a harder wood like maple or oak going to show up chain issues like this better than soft wood like pine?

 

[Brent Nowell]

From my experience the initial angle of your bore cut itself in which I mean your angle of bar in relation to the wood is a huge factor.

I come in at a 22-45 degree angle from the pulling side of the bar (bottom) into the wood and enlarge the hole slightly. I continue this until about 6” of depth or so then straighten out and find that kickback inside the wood is almost nothing.

If you go straight in with a regular chain (non anti kickback) you are halfway into the kickback zone of the bar tip on first contact. So things will get aggressive and possibly dangerous if your not careful. I have also experienced this to be more evidence with full chisel chains, again I don’t really know why (possibly a more stress I’ve cutting angle?) but again just my experience.

When I fell trees I almost always use a 75 degree hinge and a bore cut, this is imo the safest for your standard felling. When I’m telling trees I usually use semi chisel chains with an anti kick back feature. The room for error is much greater on this chain for kickback and chatter for obvious reasons.
People seem to have a problem with anti kickback, and if your just a weekend faller you shouldn’t worry. If you get an anti kickback chain with the non-curled over depth gauge, they last a while. There will come a point when you file to the anti kickback leading link but it takes a while.
The curled over depth gauges suck cause they are impossible to file down while retaining their design.

If you want to maximize chain life through sharpening then anti kickback is def not for you.
Imo the design is worth it for ease of use, but each their own. Pros and cons to each design.

 

[5155]

Brent N, can you tell more about this 75 degree hinge? I mean 75 degrees where/from what? If I can learn safe practices, it's a good thing. Thanks.

 

[SteveSr]

Brent N, can you tell more about this 75 degree hinge? I mean 75 degrees where/from what? If I can learn safe practices, it's a good thing. Thanks.

I think what he meant to say was a 75 degree face cut. I like to use a high-angle open face cut followed by a bore hinge/back cut. The angle should be as close to 90 degrees as possible to keep the trunk attached to the stump for as long as possible. With 90 degrees the tree is on the ground and should be still attached to the stump. I like to use 70 degree top cut and 20 degree undercut.

 

[Brent Nowell]

I think what he meant to say was a 75 degree face cut. I like to use a high-angle open face cut followed by a bore hinge/back cut. The angle should be as close to 90 degrees as possible to keep the trunk attached to the stump for as long as possible. With 90 degrees the tree is on the ground and should be still attached to the stump. I like to use 70 degree top cut and 20 degree undercut.

This is what I meant
If you watch the husqvarna USA video on YouTube about hinge techniques he goes into it.
This is where I learned it from

 

[Brent Nowell]

Talked about here


Demonstrated here

Starts at 16:00

Not only is this used for upright trees it is absolutely the way to go for learners, prevents barber chairing.

I am by no means an expert but I use this technique 90% of the time. Thinner trees with say a larger saw it’s no good cause you can’t get a wedge in the sides before the back strap is cut and you pinch your bar.

 

[Philbert]

However I noticed considerable vibration and bucking when bore cutting a 10" diameter piece of maple. . . . Is it related to the non-profiled rakers or is there some other sharpening defect that I should look for and remedy?

Looks like I need to go profile the rakers and inspect the rest of the chain.

Best test you can do! Profile those depth gauges round on the same chain, and let us know any difference you notice.

As @Justsaws noted, each cutter tilts back as it enters the cut. If you file a depth gauge flat, it is possible that the sharp corner might bite into the wood. If you somewhat match the curved, OEM profile, you can be pretty sure that a smooth portion will hit the wood, even if not the top. This is likely to be more noticable when bore / plunge cutting, since only a few teeth are hitting the wood when entering into the cut, and the position of the bar tip is somewhat unstable, as opposed to cross cutting.

When ripping, the roles of the top plate cutting edge and the side plate cutting edge are reversed. Guys who mill lumber often use very different filing / sharpening angles because of this. Root around in the milling threads for more info on that.

Philbert

 

[5155]

Thanks for answering guys. Don't know all the lingo and short hand here but catch on fast.
I liked the T and G cut in the movie, had not seen that prior. Thanks again.

I had cut in tornado blow downs, talk about torque on wood.
One pro logger walked off after being flicked like a bogger.
Never seen such unpredictable big logs.

To the topic, yes I've noticed flat / undressed rakers be more snappy grabby jumpy.

 

[Tin-knocker]

Maybe it’s just me but that video looked like the guy had a pretty steep conventional face cut. I bore cut most trees and lately I’ve been doing some gnarly leaners and I opt for a true open face cut and then I bore cut. The book to fell a tree by Jeff jepson is worth its weight in gold. Cheap on eBay and pretty much has all the info you need

 

[SteveSr]

Well, I have figured out how to make the problem worse...

Went out to the garage this morning and used a brass wire brush to remove the sap and sawdust buildup from the cutters that is clearly visible in the photos above.

Went out to my test logs and tried a few cuts. The first cut was dried sweet gum. Cut a cookie and bored fine. I then moved on to a dried piece of white oak. It fought a little bit but was able to bore cut it. Next moved on to some dried red oak. It fought me a little more but I was able to complete the bore cut.

After this session I noticed the start of some more buildup on the top of the cutters so I went back to the garage for a closer inspection. The cutters still looked sharp but the "hook" looked sort of rough due to being filed. Thinking that this might be part of the reason I decided to touch up the chain. This time I decided to use the diamond hone in my Oregon Dremel style sharpener. When I was done I did another inspection and the cutters looked nice and smooth... and very sharp!

The next cutting session I started again with the sweet gum log. Again it cross cut fine and also bore cut fine. I moved on to the white oak log and the saw fought back so hard that it actually set the chain brake once and I never did make a successful bore cut. Next moved on to the red oak. I was able to get the cut started but the saw bucked like a bronco mainly when the tip was in contact with the front of the bore.

In all of this I never did anything with the rakers. There was still most of the remaining leading edge profile (see photos) and a fairly gradual transition to the recently filed section. So it looks like @Justsaws was correct. For bore cutting the sharper the chain the worse it bore cuts. A corollary is that the harder the wood the worse this gets as well. Also note that this is NOT a low kickback chain, just standard Stihl RMC. This may also make a difference.

I am going on a local trail workday on Saturday to cut some more variety of material. Most of this should be considerably greener (and hopefully softer).

Anybody have any other thoughts or see any issues of the cutter profile in the photos that I posted above?

 

[wyk]

If you want to make a habit of bore cutting hardwoods you may want to consider clipping the heels of the teeth or getting a red bar/wide tip bar and see if this helps.

 

[SteveSr]

If you want to make a habit of bore cutting hardwoods you may want to consider clipping the heels of the teeth or getting a red bar/wide tip bar and see if this helps.

This is an interesting idea. However, I don't believe that it is happening in this case as the chain does cut but too aggressively. If it was dragging the heel of the cutter I wouldn't think it would bore cut at all. Wish there was an easy way to test this and confirm either way.

 

[wyk]

This is an interesting idea. However, I don't believe that it is happening in this case as the chain does cut but too aggressively. If it was dragging the heel of the cutter I wouldn't think it would bore cut at all. Wish there was an easy way to test this and confirm either way.

Every bore cut drags the heel. It's impossible not to unless you aren't pushing the bar in to the wood.