Maximum computed kickback angle 45 deg.?

I have read the "safety standard" below, but don't understand it.

Does it mean that a saw with a low kickback bar and low kickback chain will only kick back up into the air 45 degrees maximum (in the worst case situation)?

And that if it were to kickback say 90 degrees, it would be hitting you if you were standing behind the saw rather than to the side?

And does this 45 degree maximum kickback potential standard apply to electric chainsaws with low kickback chains and bars as well?

Safety Standard...
["The United States Consumer Product Safety Commission points out that key features of the voluntary standard include a test for measuring the kickback potential of chain saws and the establishment of a maximum computed kickback angle limit of 45 degrees for gasoline-powered chain saws under 3.8 CID."]

I've always wondered that thing myself, I don't know that I believe it even if that is supposed to be teh way it is. I've never had any saw kick straight in the air, pro or consumer, but I haven't used one as much as most pros or even heavier duty firewood cutters. Hope someone knows!
J.D.

The 45 degree angle can de the angle on bar tip (nose) from bar direction at which kickback can happen if there is contact with wood

I suspect that the 45 angle is referring to the max point at which the chainbreak will activate.

Harry K

a while back i was running a 394 with a 32 in bar, cutting wood on the ground. a piece rolled and caught the tip. i had the saw over my head before i got control over it again. that was the worst kick back i ever had. most guys on my crew have gotten kicked in the ass for not having 2 hands on the saw.

For the interest I recommend to put once RM (RM2) instead RS (Stihl) chain and if there is the green labelled Rollomatic bar also, U never need survive such kickbacks. With 026 I used RS an now I can tell that it wasnt worth for me of the some cutting speed advantage. Now I use RM and my 270 has not made any attempt to kicback to give me a sawing "lesson".

I get the opportunity to see chain saw kickback on a daily basis for every thing from little electric saws to the 70cc pro models!!

In a kickback situation there are two types of movement in the chain saw, linear and rotational. The linear is when the saw is pushed straight back at you, you found out about the rotational. The computed kickback angle sums up all the movement and shows it only as rotational. So for each particular saw/bar/chain combo the angle shows how much the saw would rotate if it only had rotational motion. The smaller the number the less severe the kickback danger. Low kick bars and chain have a BLUE safety rating (under 45 degrees) for use by ocassional chain saw users. The yellow safety rating (above 45 degrees) indicates it is a non-safety kickback combination.

Don't be fooled into thinking it will only rotate, a top pinched chain will shove the saw straight back at you. If you don't have BOTH hands (with fingers and thumb fully wrapped around the handle) firmly gripping the handle you will get a very good cut on the hand. I've see stats on where loggers usually get cut, number one place is on the hands because their hand slipps off the front handle and into the chain.

kf_tree said:

most guys on my crew have gotten kicked in the ass for not having 2 hands on the saw.

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I hope you take advantage of Gypo's visit this weekend and kick him in the ass, once for one handing, another for no helmet, another for cutting thru hingewood, another for no eye protection, another for not using the chain break, another for using trampolines, another for ..... does the list ever end?

Oregon Engineer said:

...I've see stats on where loggers usually get cut, number one place is on the hands because their hand slipps off the front handle and into the chain...

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Very interesting. Thanks for posting this. The more I read about this stuff, the more I am sure to wrap my thumbs under the bars, etc.

I saw a "mitt" sold which only had kevlar on the back of the left glove, but not the right. Did the stats you have seen show the most injuries to the back of the left hand? I assume they did not have their thumb wrapped under the bar?

So far as your testing kickback, I would presume that you use some sort of test jig or robot? This must be quite interesting to see. Chainsaws flying all over the place all day!

Billy Bob,
I have just that same kind of glove and use it every time I cut.

The stats do not show where on the left hand people get cut.

The kickback testing is done on a test rig which holds the chain saws by the front and rear handle and allows it to rotate about the center of gravity. A linear carriage that carries a block is released and hits the tip of the chain saw at a specific speed. The block on the carriage can be placed at different angles so it strikes the bar tip at different points in the KICKBACK ZONE. After impact of the block the carriage is thrown back and the saw rotates. The rotational and linear energy of the reaction is measured and put into a program to spit out a single number as though all the energy caused the saw to rotate.

The energy of the kickback reaction greatly decreases the life of all saws used in kickback testing. The saws are usually held in the rig with no problems, but on occasion the handles of a professional saw or the rig holding the saw will break when the block is at a specific angle to cause a maximum kickback reaction. The test technician is always in a safe location.

If you are interested I can get a picture of the rig.

Please do get a pic, that's very interesting stuff and it's good to see the in depth testing done on chainsaws.

Oregon Engineer said:

...If you are interested I can get a picture of the rig.

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Please do. This is interesting.

Also, I don't know if it is possible... (politics/budget/etc.), but it would be really educational to have a few videos of chainsaws kicking back. Perhaps on the Oregon web site?

Also there is a University professor who does high speed videos of various things. This would be interesting to see a chainsaw cutting or maybe kicking back. Here is his link...
http://www.engr.colostate.edu/~dga/high_speed_video/index.html

Pictures of kickback test rig

Here are the pictures (front and back views) of the kickback test rig used to test saw/bar/chain combinations.

You will notice that the chain saw is held by a "saw cradle" that holds the front and rear handles. The saw cradle is adjusted so the center of gravity of the saw is aligned with the center of rotation of the cradle.

You will see a test block in contact with the chain on the bar nose. The block is held by a linear carriage that moves towards the nose at a specific speed. The block can be angled from 0 to 30 degrees to determine the worst case kickback. The carriage weight is modified to be match the saw.

The saws are run at two speeds, 9,000 and 12,000 rpm. The angle of the block is varied from 0 to 30 degrees if needed, but usually the maximum impacts occur in the 5 to 15 range.

Kickback movie

The attached .mov file shows a kickback on the test rig. The movie started at 9 megs and I got it down to 1/2 a meg. It's short but you will get the point if you picture yourself behind the saw.

It took 28 seconds for me to down load the file with a cable connection, so you may have to be patient.

Watch it several times, first watching the chain saw rotate, then watch the carriage race backwards after the impact. If that saw was in your hands it would be both rotating and backing into you.

I was able to step through the movie one frame at a time by using the buttons on the right hand side of the viewer. Stepping through one frame at a time really shows how fast the saw is rotating.

Excellent movie showing just how quick this all happens and the real importance of keeping the saw under full control at all times with both hands and eyes on the job and of course the brain fully engaged on the task at hand.

Mc Bob.

Oregon engineer thanks for that, it's really interesting. Good stuff.

My gracious! That is awful......I guess that is a worst case scenario...I have experienced some mild kickback, but never anything CLOSE to that. !!!! Is the bar nose hitting a foreign object or another piece of wood usually what causes severe kickback like this?

Thank you very much for posting this.

That kickback is a real eye opener. Hopefully the only time I will experience this is by watching your movie.

BTW, I purchased some gloves which protect my left hand. After watching the movie, I think I'll get one of those protective shirts as well!

And in real working situations, not forget, that this can hapen in any direction depending from saw position