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02, Nov 2024 -

Life of a circle saw blade

Life of a circle saw blade

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If you’re involved in the filing room or managing the circle saw budget, you’ve likely asked or been asked, “When should a saw be discarded?”

Sometimes the answer is clear even to a layperson: if the saw is severely bent, cracked, or missing a piece from the rim, it’s clearly beyond repair and should go straight to the scrap metal dumpster. But what about when the issue isn’t so obvious? What guidelines do experienced filers use to decide when a saw should be retired?

Safety, safety, safety: Most filing rooms have adopted the rule that a saw is not to be welded or drilled out if the gullet or body of the plate is cracked. When plates were thicker and edgers weren’t high-speed, many of the old filers would drill out and stop a crack from getting out of hand. This practice has pretty much been eliminated due to safety regulations. The savings just don’t justify the risk to employees and equipment.

Time is money: An experienced filer understands that both time and downtime equate to money. Therefore, if a saw shows measurable signs of wear and metal fatigue, it is typically culled to avoid further losses.

An experienced filer understands that both time and downtime equate to money.

Therefore, if a saw shows measurable signs of wear and metal fatigue, it is typically culled to avoid further losses. The filer knows he can keep hammering and possibly achieve what he’s looking for with his gauges, but will the work hold up under pressure?

Consider the saw plate like a piece of elastic: after being stretched repeatedly, it eventually loses its ability to hold its shape. A saw, similarly, will become impractical and uneconomical to repair if it’s worn out. Culling a saw with a bent or creased plate should be an easy decision. However, deciding how much hammering or bench work to perform before culling can be challenging.

If a saw plate has lost so much tension that it’s as flimsy as a dish rag, it’s best to cull it. Even if tension can be restored to make the saw appear functional, it often won’t hold true or perform reliably before its next scheduled change. While straightening the plate, leveling tension, or balancing tension may be sufficient to keep a saw in operation, excessive hammering can cause metal fatigue and compromise performance.

Planning is crucial: A filer may struggle to cull saws even when necessary if the mill doesn’t have enough replacements available. Delays in ordering or stocking new saws can force filers to repair ones that are beyond practical repair, potentially leading to excessive downtime or increased repair costs. Mills with double arbors might manage to extend the life of a saw by moving it to the top arbor, but proper budgeting for saw replacements is far more cost-effective than dealing with miscut or downgraded lumber.
 
Tipping the scales: Some filers like to have a hard and fast rule when it comes to discarding or culling saws. Over the years, they’ve observed that performance and run times suffer when a saw is retipped beyond its effective lifespan. These filers often calculate the optimal number of retips for their specific operation and establish a rule that a saw will be culled after reaching this limit. For the frugal minded or someone that hasn’t studied the numbers, this will often appear wasteful. But experience and statistics usually don’t lie. Over-tipping, especially without gullet grinding, can lead to spillage, body wear, overheating, and downtime. Data is crucial when using these parameters to cull saws. Another factor regarding the tips is how many broken shoulders a filer is willing to repair rather than discard the saw. Some won’t weld any and others limit it to a percentage of tips. Certainly, the age of the saw will play into their decision to keep or cull.

Clean and cool: If any amount of babbitt is caked on the side of the saw plate, it’s a good sign that heat has damaged the plate. All babbitt must be thoroughly cleaned off before the saw can proceed with repairs. After cleaning, the plate should be inspected to determine if further work is needed or if the saw should be culled.

A seasoned filer can quickly determine whether to cull a saw or repair it for another run. First, they inspect the teeth to see if they can be sharpened or need retipping. If either option is feasible, they then evaluate the saw plate itself. They check for damage or cracks, assess its levelness, and look for problematic knots that might require excessive hammering.

In modern hammer rooms, flat anvils are commonly used. By applying a small amount of oil to the plate and laying it flat on the anvil, a filer can pull up on the plate. If they detect a slight suction holding the plate, it indicates that the plate is likely flat enough to be restored to good condition without extensive work.

Over 30 years ago, when I founded Smith Sawmill Service in Texas, the Texas comptroller classified saw blades as taxable tools, based on their belief that these tools had a lifespan of six months or more. However, advancements in high-speed equipment and thin-kerf sawing have rendered this lifespan theory outdated. Today, saws are no longer taxable in Texas under the manufacturing sales tax guidelines.

Source: Canadian Forest Industries

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