Decided to test chain types and angles today

[blis]

When your dragging a metal cutter through wood, the sharper it is the less load it places on the motor. Chisel is sharper than semi chisel....

Chisel can be sharp as semi-chisel, but the cutters profile is different, the chisel has straight edge which causes it to hit wood like chisel, while semi-chisel tries to "sweep" the wood instead of striking straight throught it, therefore requiring less power to dig in....


just my thoughts...

 

[bwalker]

Chisel cuts, while semi gouges.

 

[blis]

Chisel cuts, while semi gouges.

Still they can be of equal sharpness, cant they?

 

[bwalker]

Still they can be of equal sharpness, cant they?[/QUOTE
No.

 

[Canyon Angler]

When your dragging a metal cutter through wood, the sharper it is the less load it places on the motor.

...unless you're hogging out more wood per minute (which is what MUST happen for chain A to cut faster than chain B). In that case, the saw is being asked to do more work per minute (or create more power) which means that the load is going to increase. If the motor can't handle that load, it's going to bog, and when RPMs drop, power output drops.

In the universe as we know it, you simply cannot say that a particular chain BOTH cuts through a given log faster AND in doing so creates less load/resistance for the motor. If it cuts faster at the same chain speed, each tooth is going to have to remove more pounds of wood -- which is going to increase the load.

 

[bwalker]

Never had a chisel chain bested by semi chisel..

 

[B_Turner]

Interesting video, engineeringnerd, thanks for taking the time to test and post.



Hmmm...I would say just the opposite. Semi-chisel chain isn't necessarily less efficient -- it's less aggressive. Here's why:

If, as you claim, a chisel chain should cut through a given log faster than a semi-chisel chain, then it follows that a full-chisel chain will put more of a load on a motor because it's doing an equal amount of work in a smaller amount of time (power = work/time). In order to do an equal amount of work in a shorter amount of time, with all other things being equal, the load MUST increase. There ain't no two ways about it.
.

I don't want to offend you, I think your concept of severing wood fibers is incomplete. It is all about efficiency of severing and removing wood fibers. That is why a fresh square ground chain is easier to pull, as it takes far less effort to cut with that highly efficient side cutter on the tooth (assuming crosscutting here). If a (correctly) sharp chisel is cutting slower than a semi chisel then there is another issue, like way much wood engaged for the saw (and operator error as well) and or depth gauges not limiting the cutter enough for an efficient and appropriate cut.

I have run square round and semi chisel back to back on various saws for hours on end many times. I can tell you that my 066 and 395 pull a 42 inch bar completely buried much more easily with fresh square ground chain as compared to fresh (or off the reel) semi chisel. I consider that a good example because pulling a 40 inch cut is close to the reasonable limit of those saws.

I suspect something is not perfect about either the sharpening of those chains, and or of the tuning of the saw.

To answer the question about why so much semi chisel is run on saws, it primarily is because in the real world of chainsaw users, it is much more forgiving to sharpen and stays sharper much longer.

For certain wood I do run semi chisel. I have approx 25 loops of sharpened semi chisel in my chain drawer at any one time for use. From 60 dl to eight 135 dl chains.

Basically I am saying what TreeCo said a couple of posts ago, but he said it in 20 words and I used 300.

 

[B_Turner]

I just thought of a simpler example about efficiency.

Consider how much easier it is to cut a piece of paper with a razor as compared to a table knife.

 

[blis]

I just thought of a simpler example about efficiency.

Consider how much easier it is to cut a piece of paper with a razor as compared to a table knife.

That difference is caused by different angle of blade and different edge profile, but i see where your getting, different cutter cuts better/worse in different materials...

 

[B_Turner]

That difference is caused by different angle of blade and different edge profile, but i see where your getting, different cutter cuts better/worse in different materials...

I used that example as a simplified case where it is clear that amount of material severed/removed does not directly correlate to amount of required effort.

Same with cutting wood. Can't assume that same quantity of chips between chains means same amount of effort involved.

 

[Canyon Angler]

I'm curious what the height of the rakers or depth limiters or whatever you want to call them was on these 2 chains...it seems like the full-chisel chain was hogging and bogging...

 

[Engineeringnerd]

B_Turner

I may have to try some of this square ground chain sometime. The log is still there, but time is a little short.

What type do you run in 3/8" and where do you recommend getting it? Also, how do you sharpen it, by hand or with a special grinder?

 

[bwalker]

it seems like the full-chisel chain was hogging and bogging...

the rakers need not be excessively low to do this. Wacky angles can do it also. The biggest offender is filing with the file too low on the tooth.

 

[B_Turner]

B_Turner

I may have to try some of this square ground chain sometime. The log is still there, but time is a little short.

What type do you run in 3/8" and where do you recommend getting it? Also, how do you sharpen it, by hand or with a special grinder?

I personally like Stihl RSLK. Oregon CL or CLX is popular as well, although off the reel it isn't quite a sharp as Stihl in my experience. I buy reels, and I am told it is getting harder to find some places. Still fairly common, though, as some folks buy it square and then resharpen it round. Oregon perhaps sharpens by hand a bit easier. Both cut fine when resharpend, which is when square really sings.

The rub is for most or us mere humans perfect and timely hand sharpening of square ground is a challenge so we need a grinder. And they are pretty expensive.

There are many threads discussion hand filing square, but I leave that to folks with more extra time and energy left over than me.

On the subject of sharpening chains, I personally feel it is critical for one to learn to visually inspect a chain and see how good the edge is. If you don't learn to do that, you don't get all the feedback available when you resharpen. The subtlties of what you see take time to learn, but it is very useful in learning to always do a good job. Ever resharpened a chain and then find it didn't cut well? Then you weren't paying attention.

 

[Kneejerk Bombas]

...unless you're hogging out more wood per minute (which is what MUST happen for chain A to cut faster than chain B). In that case, the saw is being asked to do more work per minute (or create more power) which means that the load is going to increase. If the motor can't handle that load, it's going to bog, and when RPMs drop, power output drops.

In the universe as we know it, you simply cannot say that a particular chain BOTH cuts through a given log faster AND in doing so creates less load/resistance for the motor. If it cuts faster at the same chain speed, each tooth is going to have to remove more pounds of wood -- which is going to increase the load.

Did you ever see a karate expert break a pine board with his head? If you want to have fun, turn the board 90 degrees. It won't split.
This illustrates the difference in grain direction. Understanding this, will tell you why different tools can be dragged through wood, and it takes different amounts of effort.
Push a wood chisel along a pine board, with the grain. Now, do the same thing across the grain. A bit harder, hey?
Understand that as cutter is dragged across wood, the side-plate cuts wood fiber, the top-plate simply separates the fibers.
A full chisel only cuts about .020" of fiber as it moves along. A semi-chisel is cutting at least 15% more fibers to move the same distance, because of the radius of the cutter.

 

[Diesel JD]

RE: the square chisel...I noticed in a post here awhile abck that Stihl recently obsoleted their chisel files. I hope this does not mean that they soon plan to obsolete square chisel. As far as depth gauge settings, Oregon's factory setting is .025" for all its square chisel chains. Oregon still selss plenty of square chisel, and I like the 72CL. On a 32" bar and a 372, it needs to be 72CJ or Stihl 33RSLFK, the full skip versions. The square chisel in my experience was ever so slightly faster than the standard RS round chisel in my wood which was not nearly as thick or as hard as yours, it was sweetgum, approximately 18"dbh on a 24" bar, 390 saw, full comp. chain, and water oak same setup. I bet I would have liked it more after the first sharpening if it had been sharpened by an experienced hand filer or with a grinder. Instead I filed it using the instructions from the Oregon book and a 3 corner chisel file, and it still improved its sharpness somewhat. I wonder if I showed a pic of my square chisel if people could tell how my work looks? I wouldn't mind teh critique. J.D.

 

[Canyon Angler]

A semi-chisel is cutting at least 15% more fibers to move the same distance, because of the radius of the cutter.

Hmmm...I guess I never thawt a that! :blush: DOH! :taped: