Swing Blade Safety

How dangerous is a swing blade sawmill? Operators kick the topic around. June 30, 2007

Question
I know some of you swing blade sawyers have hit trash, metal or lost teeth. Is it just my lack of knowledge? Or is my common sense saying "Danger, no guard!" Something to consider in purchasing a new mill. Would chaps really help in a catastrophic failure? And for the 3/32" thick piece of lexan (bullet proof glass), it takes over 1/2" thick to stop a 22 shell. I would really like to know before it happens how a 21.5" circle blade with 5 teeth at 2000 RPM really does react to metal.

Forum Responses
(Sawing and Drying Forum)
From contributor I:
I've hit metal a few times with the swing blade. Anyone that does much sawing will. It's a bit of a non-event - you hear a zing as the carbides chip off and the saw stops cutting properly. If it's a big enough piece of metal, the carriage just stops. Remember, with a big circle mill, you have 100+hp driving the saw and the log is being fed in fast and with considerable power. The power and momentum is there to bust shanks off the blade and fire them around the landscape like bullets. With a swing blade, it's generally being fed in with a couple of pounds of hand feed pressure.

If you hit something solid, the carbide tips disintegrate and the saw stops cutting. Wearing a face shield and chaps is recommended, but that's mostly for flying wood chunks. There simply isn't the power involved to launch big, fast pieces of shrapnel like a big circle saw can.


From contributor R:
The rim speed of the circular blade is about 190 fps given your numbers. A traditional 22 long rifle bullet travels about 1100 fps coming out of a rifle. Since the kinetic energy is proportional to the velocity squared, a carbide tooth of the same mass as a 22 bullet would have (1100/190)^2 = 33x the energy as the bullet. Hence you don't need as thick of lexan.

Now, I don't have any idea if what they provide is thick enough or not, but at least it's not necessarily as bad as it may first look.


From contributor J:

Someone is thinking way too hard. I have hit metal, from nails to lag bolts, fence posts, insulators. I have noticed that after hitting metal, the shrapnel has left marks inside the wood. I would reckon that the velocity of the shrapnel would be greatly reduced by the wood it comes in contact with. As with anything with sharp edges or a motorized tool, you've got to be on your sharpest edge... You know when you hit metal - be alert and prepared. I have been cutting with my Lucas swing blade since 2001, and the only things that I get hit with is sawdust. Sometimes it's zinging fast, but that's why you don't mill lumber in your shorts. Ear and eye protection. I wear a woodworker's apron - keeps the pitch off my belt area and stops the sawdust.

From contributor U:
I too used to worry about that until I hit metal a few times. It is foreseeable that a tooth or metal object could be launched, but the fact is the metal you hit is usually surrounded by wood, as is the tooth that's getting wrecked.

From Professor Gene Wengert, forum technical advisor:
I have been in commercial sized circular mills and have seen little holes in the roof and walls where a tip has flown off (or maybe a shank). It would seem that standing in a direct line with the blade is not the best idea.

From the original questioner:
Thank you for all the feedback. I feel a little better now. One last question. And this one is really out there. Has anyone ever heard of, or has it ever been factory tested, what would happen if someone accidentally rotated the carriage before clearing the log? Seems like it would just pop off those 5 each 8mm screws and send the blade out like Frisbee from hell?

From contributor J:
I must be missing something… Rotating the carriage? I have swung the blade prematurely before, hitting the log (no damage to the saw, bruised ego a bit), but one would have to be nuts or stupid to swing the carriage around (lift off the tracks and double cut) with the darn blade still spinning. I'm sure that's not what you're talking about… Is it?

From contributor I:
Again, you are only swinging the blade by hand. If you goof up and swing it before you clear the log, you cut a bit of a gouge in the log and feel like an idiot. The blade is securely held in place against the arbour by the bolts you mention. It is well supported by the arbour behind it and it would take a huge amount of force to break it free. Much more than you are going to be able to exert on the hand lever.

I believe a blade has come free once, but that was due to an operator modifying the holes in the blade and using incorrect mounting bolts, and yes, the result was fatal.

As the mills come from the factory, they are very safe to operate. The main danger seems to be from flying wood chips and small offcuts/knots that get kicked back by the blade. The safety gear gives you decent protection from that, and it's usually flung away from the operator. It is important to keep bystanders back from the cutting side of the mill, though. All sorts of stuff gets flung there.


From the original questioner:
Are there drive pins in the arbor as well as the 5 screws? If so, that would distribute the force better than just flat head screws. I would think there would be a huge amount of force at the arbor if the blade was rotated and the teeth got enough bite to stall the engine. In which case there would be far more force generated than just what you apply to the handle. As someone once said, "makes me shiver." Regardless, this is great information and I think it's worth discussing.

From contributor J:
I believe it's a castle nut on the end, with a lock device tab bent over into the land. My blade did come to an extremely fast stop when I hit some fiberglass in a piece of log. Everything was fine, instant stop.

From contributor T:
I'm pretty safety minded. If you use the Lucas according to the manufacturer's instructions, it is probably as safe or safer for the operator, nearby property, pets, and bystanders than weed trimmers and other lawn and garden equipment. Driving to and from the site and handling logs is probably much riskier. I think you'd really have to do something stupid to injure yourself.

From contributor U:
I've heard of large circle mills kicking whole logs off the carriage. I think I read it somewhere on this site. The circumstances, if I remember correctly, were in cutting logs that had ring shake. The saw cut a knot loose (?) allowing it to slip down (or up) against the blade inside the cut. This wedged the blade in the cut and all the energy of the saw... If something like this could happen to a large blade, why not a smaller blade on a swing mill? I'm not saying it has enough energy to toss the log, but enough to kick the log sideways and make the carriage jump.

From contributor B:
Been running my Lucas for 11 years - cut around 500000 bf. I have hit rocks, nails, one glass insulator, barbed wire, high tension cable and armour piercing bullets. Besides a few chips getting under my glasses into the eye, I can say I've had a few knots hit me in the leg for a twinge and once that I may never forget, a small chunk (knot) swung out and caught me in a very unfortunate area.

From contributor J:
Ouch! I think all swingbladers have had that unfortunate experience once or twice… Makes ya think that a cup might not be bad safety equipment.

From contributor S:
There are inherent dangers in sawing, and safety is the operator's job. Always ask what if and is there a safer way. Wear all the safety gear, keep your equipment in top shape and follow the proper procedures.

All that said, I managed to take a direct hit in the left on a demo job about six months ago and the memory is still fresh in my, err... mind. It is funny now, but at the time I didn't know if I was going to pass out, soil my underwear, throw up, die from internal bleeding or ever be able to stand back up. It seems that the older you get, the less tough you get in that area!


From contributor I:
"If something like this could happen to a large blade, why not a smaller blade on a swing mill? I'm not saying it has enough energy to toss the log, but enough to kick the log sideways and make the carriage jump."

Yes, you can pinch a blade due to internal tension, foreign objects, etc. This can kick the log off the bunks or even pop the carriage up off the rails. But the mills just don't have the spinning inertia or the horsepower to throw large objects around with any great speed.

I would also suggest this is one of the reasons that the manufacturers keep the power of the mills down below 30hp. As the mill is only held on the rails by its own weight and controlled by hand, I can see things getting crazy if you had too much power involved.

If you try to rotate the blade over the log, only the tips bite into the log, dig a small gouge, then the side of the blade is rubbing on the wood and you can't rotate any further. About this point you wake up and kick yourself. I don't think it would even be possible to stall the saw. The other mistake is to swing the saw when it's low to the ground and have the blade contact the metal cross supports. That's about as exciting as it gets, but just results in an expensive zang noise and shattered carbide tips. Like the guys have said, small bits of wood can get thrown with painful force, though.


From contributor P:
By far, the most excitement for me is when I lose focus and forget a blade flip. Picturing how you work when doing your own off-bearing. Let's say you have just cleaned a left-hand edge and have moved right 8-1/4" to supposedly make your right hand edge of the next board by pulling back with the blade vertical. Something in the environment (or something not going on in the old gray matter) makes you omit the step of flipping the blade to vertical.

The next thing is that feeling that you are running for your life from the saw, as it scares you - big time! This particular faux pas is one which you remember a long time. That's why Peterson has that nasty label:

"WARNING! FAILURE TO... MAY RESULT IN INJURY OR EVEN DEATH!"

I have cut concrete, bullets, screws, nails, fence. No problems. It's only when my brain slips a gear (as previously confessed) that I get a scare. The guards always do their job. When I am double-cutting, however, it is time to pay extra attention to loose slivers or knots or waste which might get thrown.


From contributor U:
Okay, so it can knock the carriage loose. But does that mean it's possible the carriage could fall off the rails? Possibly with the blade still spinning?

The bandmill I operate has safeties that wrap down under the rails. These keep the head from falling off the track when you hit a foreign object/stop too hard. (Some who own this same model have removed these safeties, for reasons unknown, only to have a minor disaster later.) Do swing mills have safeties like these?


From contributor E:
My Lucas 613 just uses gravity to keep in on the rails. I've pinched the blade a few times, but other than a small buck in the carriage (and ceased forward motion), nothing happened.

From contributor P:
No, thankfully, the saw can't come off the carriage on a Peterson swing blade. The vertical blade position guard acts as a retainer. It can jump enough to cause the two traversing rollers to disengage - to jump their track. It is a simple operation to get things back into proper placement. This jump is actually a good thing: it helps to reduce the amount of power transferred to the log, when one goofs up. I can imagine that this feature also prevents damage to the mill frame.
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