SAW SHOP: The HINGE

By Bryan Wagner, Chainsaw & Logging Safety Trainer

Hello everyone! Last quarter we talked about proper face-notching. Remember, both cuts of the notch must meet. When we face-notch a tree, we are actually setting up the hinge length. The notch must be at least 80% of the tree’s diameter. That means you will have hinge-wood across at least 80% of the stump if you don’t “bore” the heart.

The hinge has two essential functions. Hinge-wood tries to keep the falling stem from rebounding if an object is struck on the way to the ground. The notch angle will tell the hinge when to release.

We try to use a 70 – 90-degree notch angle. The “open-face” notch allows the hinge to control the stem through most of its controlled fall to the ground. The theory is, the energy to rebound has been spent. The hinge on a tree serves as the steering wheel. An accurate face-notch leads to a precise hinge set. Accuracy is a significant safety issue in any felling scenario. Accurate felling in a select-cut, or SMZ felling, keeps the timber-cutter safe from being struck by falling or thrown objects. If you don’t brush or hit surrounding timber, nothing gets thrown back at you! The tree goes where the hinge tells it to. This is great if the hinge holds! If the hinge-wood breaks, the tree will go to where the tree is heavy too!

Remember, the weighted side of the tree is the BAD-SIDE! Your body needs to stay on the good side as much as possible.

OK, now let’s talk about hinge thickness. The basic rule is 1/10th of the Diameter at Breast Height, DBH. Using the formula, a 20” DBH tree would need a 2-inch hinge maximum. If we go thicker, some fiber pull may happen. The next question is, what species of tree are you cutting? Long fibered trees such as Sweet Gum and Yellow Pine don’t usually require the maximum hinge thickness. Their fiber is flexible and works well. Short-fibered trees such as White Pine or Soft Maple usually will be given the maximum “called for” hinge thickness. Short-natured fiber can break before it bends!

To sum up hinge thickness, I will usually use one inch of hinge on a 20” DBH Sweet Gum. If the same tree was a Soft Maple, I would possibly go with a 2-inch hinge.

Forestry Mutual requires hinge-wood to be continuous across the stump, or if the situation exists, the timber-cutter can center-cut the tree and leave

THE HINGE

(2) corners. I will “punch’ the center of a tree if the diameter is more than twice the bar length or if I have a “high-dollar” that can’t have pulled fiber. On a closing note, make sure your hinge is “set” in good wood. Root fiber doesn’t have the strength to control the tree’s fall to the ground. Make sure your face-notch is set behind the root fiber and is in “good wood.”

OK, let’s change the subject. I can’t talk enough about a full canopy of leaves in the woods!! Visibility in the winter months is usually good. A quick look-up can reveal danger from above. Now, with the fresh green leaves, we really need to look for overhead hazards. I would recommend going over the “Heads-Up” program for your next safety meeting.

- Use approved personal protective equipment (PPE) for head protection. Look and scan at least 50 feet ahead on your path of travel.

- Look and scan at least 100 feet ahead for overhead hazards.

- Don’t place yourself under any object that can fall or move due to gravity or the loss of hydraulic pressure.

- Maintain at least two tree lengths from any felling operation.

- Be visible!! Wear high visibility safety colors.

- Maintain communication with anyone in the work area.

- Never walk into a work area with running or moving equipment until the equipment is stopped, engine cut-off, and implements grounded.

Use proper manual felling techniques. Accurate directional felling avoids risk in the manual felling process.

- Constantly scan for all hazards!! Avoid slick bark, logs, or limbs. Stump holes, rocks, and vines are to be considered safety risks.

- Wear high visibility safety colors.

Be seen!! Where have you heard that before?!

- When not cutting, the chain brake of the chainsaw must be engaged. More than two steps with a running chainsaw require the chain brake to be activated.

- Stay on the “uphill” side of felled timber and stems.

- AGAIN, constantly scan for risks and hazards that could result in injury!!

As always, if we can help your safety program in any way, please call. It is our pleasure to help. Next time we will discuss the escape and the back-cut plans during the felling process. Until next time, be safe, LOOK-UP AGAIN!!