High tension
can help stop blade wandering.
I agree with about 99% of this below. If the saw can get to 25000 to 30000 psi that's all you will ever need(many old saws could never reach this without ruining the wheels)). The blades he suggests are exactly the blades in my shop(I do not use the super low tension blades - 7000 psi, they do not work well with my particular saws, the Timberwolf - 15- 20,000 psi - do work for me) and I have the same experience with the Laguna blades they snap and are not as good as other blades out there.
From
SoloWoodworker.com
Blade Tension
The minimum tension for a safe cut is slightly more tension than just enough to make the blade stop fluttering, no matter what type of blade. Set the guides as far apart as possible, and increase the tension until the blade runs smoothly - or decrease the tension until the blade starts to flutter, then increase it slightly. (On many saws you have to change the tracking after changing the tension.) Timberwolf recommends that you use their blades at this minimum tension, often around 7-8,000 psi, while others often recommend a higher tension if your saw can handle it. The Bladerunner/Wood Slicer typically is run at 20,000 psi. The Lenox carbide blades are typically run between 22,000 and 30,000 psi - I shoot for about 25,000 psi.
There are three confusing factors involved in blade tension...
Force is the pull of the spring - pounds. It is proportional to the amount the spring compresses until the spring's coil loops contact, so can be measured by the amount the end of the spring moves - the position of the end of the spring.
Stress = Force divided by area of cross section - pounds per square inch. If a blade is twice as wide, then there must be twice as much force to get the same stress on the blade. If the blade is twice as thick, there must also be twice as much force. And, of course, twice as wide, twice as thick needs 4 times as much force.
Strain is the amount the blade stretches, proportional to stress.
Stress (not force) is the key factor in blade tension. A low tension blade typically runs around 7,000 psi stress. High tension blades often run as high as 25-30,000 psi. The force you have to apply (the tension knob on the saw) is a lot greater for a large blade, but the tension, measured in psi, is the same for the large and small blades. Since it is related to the cross section area of the blade, the stress doesn't depend on the thickness or width of the blade, but the force required to achieve that stress (blade tension) does depend on the width and thickness of the blade.
Bandsaw tension gauges measure the compression of the spring (proportional to force), then indicate the appropriate setting for different blade widths. Most bandsaw gauges don't specify what thickness blade they are calibrated for, which is why they may be perfect for one blade, but are often misleading for other blades. My bandsaw's indicator says it is for a blade .019 inches thick (I have never had a blade that thin). Therefore, on my saw, if I use a ½ inch blade .035 inches thick, the tension indicator on my saw needs to be set for a one inch blade to get the recommended tension on the thicker half inch blade.
Measuring stress is done by measuring strain, in other words, measuring the amount the blade stretches. The elasticity (Young's modulus, E) of most steel is 30 million psi. The elongation L is the Stress divided by E. If we have 30,000 psi stress on the blade, the blade will elongate (stretch) 30,000 / 30,000,000 or 1/1000 of it's length. If we measure over 10 inches, we should see 10/1000 or .01 inch stretch in those 10 inches. If we see .005 inches elongation over 10 inches, we have 15,000 psi blade tension. For each .001 inch of elongation measured over 10 inches, we have 3,000 psi of blade tension. Measuring over the longer distance is generally more accurate. Once you establish how far apart you can connect a measuring device to your blade, I suggest making a chart for each thousandths of an inch strain (stretch), and the corresponding stress (blade tension).
On my saw, I can easily measure 12 inches apart. Using the numbers above, that means I should get 12/1000 or .012 inches stretch at 30,000 psi, or .001 inches for every 2,500 psi. Therefore if I want 25,000 psi, I tighten the blade until I get .01 inches stretch. It doesn't matter what size blade I use, the .01 inches stretch is 25,000 psi. Of course, if I have a big blade, I will have to use more force - tighten the wheel a lot harder - to get the same blade tension than the force I would need to get that same tension on a small blade.
Measuring should be done with the blade at a constant (room) temperature... when the blade gets hot through use, it will expand - comparable to the amount it stretches from tension.
You can buy a bandsaw blade tension gauge (that really measures strain) for $135 to $350, or you can make one from a cheap ($7) dial indicator and a couple spring clamps. Usually there is a connector on the back of the dial indicator, such as this, that can be clamped to the blade.
refer to his site for pics -
http://www.solowoodworker.com/tools/resaw.html
An L or T shaped set of scrap wood allows the probe to be connected to the blade as far away as convenient (for greater accuracy), with whatever offset is required to align with the dial indicator. In my case I use a scrap of wood that allows the clamps to be 12 inches apart.
Therefore the chart for each thousandths of an inch stretch with the clamps 12 inches apart indicates 30,000,000 /1000 / 12 then .001 inches stretch = 2,500 psi blade tension, .002 inches stretch = 5000 psi, ... .009 inches stretch = 22,500 psi, .010 inches stretch - 25,000 psi, etc. That chart was taped to the side of my machine for a long time, but is so simple that I just remember it now. (Remember that the dial indicator doesn't have to be set to zero... just note the difference as you tension the blade.)
Or you can do what the majority of bandsaw users do - just make some cuts and if you get good results, be happy and keep going.
Choice of blades
For resawing, the width of the blade should be close to the maximum the bandsaw will handle. A smooth cut is very important, so an investment in a carbide tip blade is worthwhile. To use the maximum size, every guide, adjustment, and clearance may have to be in a specific "perfect" position. Therefore, to allow easier adjustment, some argue that one size less than the max is ideal.
The number of teeth per inch (tpi) depends on how fast you are sawing and the thickness of your workpiece, but for starters, consider 3 tpi a large number for resawing.
How long does a carbide blade last?
A recent discussion on the MiniMax User Forum provided some insight
A person doing a lot of resawing made the comment that "a single person in a furniture shop may not have to change their blade for years." That is me - I cannot contribute personal experience to lifespan for heavy resawing.
Further discussion on that forum suggested that 600-800 linear feet of resawing curly tropical hardwood, 6 or more inches high, might wear out a blade for resawing, but it would still be adequate for other less demanding uses. Highly abrasive wood might kill a blade in 400 linear feet. Those results were confirmed by another user, for both the Lenox TriMaster and Woodmaster CT. That doesn't sound like much, but it is probably more than a full day's work, and equates to a blade cost of about 15 cents per linear foot resawed.
My current favorite blade (1 inch Lenox Woodmaster CT) has 1.3 tpi, .035 inches thick, kerf .051 inches. The Woodmaster CT only comes in 1 inch, 2 inch, 3 inch, etc. Another favorite is the
Lenox TriMaster which alternates between 2 and 3 teeth per inch, .035 thick, and comes in a wide choice of widths including 1 inch. The TriMaster has more teeth, with larger pieces of carbide for each tooth (so the kerf is .065 rather than .051 for the Woodmaster CT), and with the extra carbide costs proportionally more than a
Woodmaster CT. My bandsaw will support a blade wider than one inch. However, even though wider blades are theoretically better, the readily available wider blades are also much thicker, so I only use 1 inch wide blades.
My favorite source for Lenox carbide tip blades is
Industrial Blade - excellent service and the best prices I have found (1-800-SAW-BLADe in California).
The
"Wood Slicer" (from
Highland Hardware), also sold as the
"Bladerunner" (by Louis Iturra) has a cult following for resawing dry hardwood. It is a very thin blade (.022 inch, .03 kerf) which removes less wood and requires less power. It has variable tooth pitch which runs quieter and smoother, and requires less tension (20,000 psi - see below), With less metal doing the cutting, it doesn't last as long, but it is far less expensive than a carbide tip blade, and gives very smooth cuts.
On one forum, one person had great results with the Laguna Resaw King, but another person's Resaw King blade broke, and Laguna said it was his fault for excess tension, even though they had refused to specify the recommended tension. I have tried the Resaw King from Laguna, but prefer the Lenox blades.
If you are sawing wet (green) wood, such as milling lumber or cutting bowl blanks, you need a wider kerf (the wet sawdust expands) and perhaps a thicker blade. None of the carbide blades I have seen are suitable for cutting green wood. Of course, for bowl blanks you will be cutting curves, and therefore want a narrower blade as well. Many people use a 3/8 or 1/2 inch wide blade for bowl blanks, in a special "model" blade designed to cut green wood.
For non-carbide blades I use the highly regarded
Timberwolf blades. They are designed to operate with a lower tension, which can be an important factor with cheaper bandsaws.
Suffolk Machinery is the importer/distributor, has a website with lots of good info about Timberwolf blades, but they only take orders by telephone (1-800-234-7297 in New York), with very knowledgeable operators, quick service, and low prices for these "premium" blades. Watch their web site for occasional "buy a few and get one free" sales.