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Looking at the teeth of a chain saw, I believe the chain moves from right to left while cutting.

It has two wedges A and B.

I've never owned a chain saw, so I've been trying to visualize how these two wedges work.

And I feel stuck because the wedge A seems unnecessary. Also it doesn't look that sharp and it seems to block the sharper wedge B. I'm dying to know the purpose of wedge A here. Appreciate any help. Thanks!
enter image description here

hazzey
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sadhvika
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    Just a guess. But if you look at B then you see a vedge on top at the bottom of it you have the cutting surface. From this you can deduce that the purpose of A is to keep the wood at a suitable distance away from the chain. – joojaa Aug 23 '18 at 05:00
  • @joojaa Do you mean the wood just slides over the wedge A, and the actual cutting is done by only the wedge B ? I think it makes sense... Thank you for responding :) – sadhvika Aug 23 '18 at 05:15
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    Yes, the purpose of the wedge is just to guide the cutting process. – joojaa Aug 23 '18 at 05:31

2 Answers2

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The part you label A is the depth control to stop B cutting so deep it blocks. This depth control only works on a hard material like wood, on flesh the blade cuts down to the base of the chain - experience speaking here - I had a blade do its final stop in my leg...

The shape of B is dependent on the purpose of the blade - some have a flat top and angled face with no wedge - also the size of the blade is a factor.

When you sharpen your own blades you understand how they work and the blades do have the angle information required in or on the box.

Notice the difference in the cutting edge A:

Speedcut blade shape from Oregon http://www.oregonproducts.co.uk/en-gb/products/forestry-chainsaw.html

Solar Mike
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  • Ohh can't imagine the torture you had endured. There is a saying in our native place that goes something like - If you don't have a scar on your body, you're not a man/hero - If I understand correctly, depth control wedge fails on soft tissues as the tissue gets easily folded between the two wedges, then the sharp edge just cuts everything it sees. I think I get this. Thank you so much :) – sadhvika Aug 23 '18 at 06:21
  • It seems the sharp wedges have angles with alternating pattern of $x^{\circ}$ and $(180-x)^{\circ}$. I want to see chain saw cutting something in slow motion. I'll google.. Thanks again. Have a nice day! – sadhvika Aug 23 '18 at 06:25
  • I feel angles are chosen $x^{\circ}$ and $(180-x)^{\circ}$ so that the wedges cut the wood from both left and right of the chain saw. I still have to think a bit on how top and bottom are cut.. – sadhvika Aug 23 '18 at 06:35
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    The blades are “handed” one bends to the right and cuts the right-hand corner, the other left.. on the lefthand of the image is the left corner cutting blade - blade travels to thecrught. – Solar Mike Aug 23 '18 at 06:40
  • My cut was about 18mm long, but the depth and shape of the tooth... bled like a stuck pig, no damage luckily - except to my ears when my mum found out... :) – Solar Mike Aug 23 '18 at 06:41
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The first issue: the most important cutting edge is actually on top of the link, a segment curved towards the middle:

enter image description here

The blade on the side is secondary, just for clearing any remains of whatever might have sprung out due to material flexibility.

These links alternate the sides, so that the overhang isn't excessively long but the cut provides a gap wide enough for the entire chain to fit. Otherwise you'd be stuck with a very shallow cut and unable to get anywhere deeper than what the blade sticks above the chain!

Next: Cutting wood with a chainsaw is subject to the same set of rules as any machining; lathe, CNC mill, drill on a boring machine - all the same rules:

enter image description here

There's the blade angle, speeds&feeds, material properties - and there's the cutting depth, which is an important parameter that accounts for power, material durability, chip properties and so on.

And the blade can't be right above the chain, because there would be no room left for the chip! It must be offset from the chain (by the distancer "A") to fit all the material it removes before it exits the cut and can be ejected!

SF.
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