Swingmill Blades – Taking the Mystery Out of ‘Swingmill’ Blades
(Editor’ Note: This is the first in a series of articles about saw blades for swing blade portable sawmills, also known as ‘swingmills.’)
Have you heard some good things about ‘swingmills’ (swing blade portable sawmills) but don’t know enough about the blade technology?
Even owners of these sawmills may have not gotten around to reading the whole manual yet.
Here are answers to some of the simple questions in order to de-mystify the swingmill blade. Much of this information also will be relevant to the technology of double-bladed portable mills, too.
A swingmill has a single circular blade that pivots. It moves forward sawing in a horizontal plane to make the first cut, pivots to the vertical plane at the end of the log, and then moves back to its starting position as it saws in the vertical plane. Your dimensional board can now be removed from the log, completely edged and square.
Peterson Portable Sawmills in New Zealand was the first company to design and manufacture swingmills in 1989, followed by Ecosaw and then Lucas in Australia in 1994.
The holes in the saw blade are called strobe slots, where small planer knives or ‘strobe knives’ can be mounted.
Many sawmillers hate sawing fibrous cottonwood or poplar because the timber rubs the side of the blade, causing friction and heat. If you install strobe knives in the slots, they clean away the rough surfaces in the sawing path and allow the blade to continue sawing unhindered. Strobe knives can make all the difference between a 2-hour job and a 2-day job! Plus, the slots allow water to travel through and lubricate both sides of the blade, reducing uneven heating.
Figure 2 shows a perfectly good, working blade from the field. This particular one is five years old. This sawmill owner works his blades real hard, but the blade nevertheless is in very good condition. The marks and colors are normal; the brownish areas behind the teeth are just sap and sawdust marks. This blade was left in the rain a few times; you can spot some rust pitting in the dark, dotted areas. Minor pitting like this is not a big deal. Nevertheless, a blade should not be left wet for weeks at a time because pitting can get quite deep and weaken the structure of the blade.
When you look at Figure 3, you may think this blade is destined for the scrap heap – but not so! This blade is still fine. It is just covered in surface rust from moisture in the air even though it was under cover during long-term storage. All you need to do is give the area around the mounting holes a light sanding with very fine sandpaper to ensure it can mount flush and tight to the hub. The rest of the rust will come off with your first few boards.
The number of teeth on a blade impacts performance. For example, fewer teeth with a thinner tooth are better for cutting hardwoods, yet more teeth and wider teeth perform better in soft or fibrous species. More teeth give a better finish but can be slower cutting as each tooth is only taking out a small bite.
It’s important that a manufacturer get the right balance between sawmill horsepower, blade thickness, number of teeth and tooth width to achieve optimum performance.
If you are considering buying a replacement blade from a company other than the sawmill manufacturer, you may need to think again. Each brand of swingmill has carefully designed their blades specifically for their mill, unlike bandsaws, which are often generic. A swingmill blade’s design, shape, and patterns are automatically copyrighted to the original designers, even internationally.
Inferior replacement blades can make sawing a real nightmare. If the blade is too thin, it will vibrate, be hard to push and cut rough. Safety also has to be considered when it comes to details like ensuring the blade screws are completely level with the surface of the blade. A blade that has CE Safety Certification should have a maximum rpm stamped on the body to ensure that it is not operated beyond a safe working speed.
And if you ever have a problem with your original factory blades, you can always get support from the manufacturer. Considering that a good blade can last six to eight years or more, it is a smart decision to buy a new one from the original designer.
(Editor’s Note: Future articles in this series will focus on re-tipping and sharpening, maintaining the plate and gullets and tension, blade adjustments, and maintenance and running costs.)