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Bandsaw Blades Answers

The Bandsaw Balancing Act Part 2
The following article was originally published in Wood News Issue 21, Summer 1988.

Blades available

It should be noted that all bandsaw blade stock is not created equal. In the United States, most woodcutting bandsaw blade stock ranges in thickness from about .018 to .035 inches. Most of the blades we sell at Highland Woodworking are .025 inch thick. This thickness works best on bandsaws with wheels between 11" and 16" in diameter. Thicker blades can have a tendency to fatigue too quickly on smaller wheels. Bandsaws with very small wheels, 7" or 8", should use blades about .020" thick, or thinner if possible. Bandsaws with wheels 18" and larger can use blades between .025 and .035" thick.

Most readily available blades for cutting wood are carbon steel blades. The bimetal blade was designed to cut metal. While it can be used to cut wood also, the bimetal design has some limitations.

The regular carbon steel blades come in a variety of widths and tooth styles. In woodworking, three tooth styles account for most use; standard, skip, and hook.

Standard Tooth

The standard tooth bandsaw blade (sometimes called raker tooth) produces the smoothest cut. It works best for crosscutting. Because it has a tendency to follow the grain, it should not be used for ripping or resawing except in special cases.

Skip Tooth

The skip tooth bandsaw blade looks like the standard tooth after a fight. The distance from the tip of one to to the next (tooth pitch) is farther than on standard, giving the appearance of teeth missing. This allows for greater gullet space which removes sawdust from the cut. This tooth style is better than the standard when cutting thicker words and for ripping. Like the standard tooth it has 0 degree rake angle.

Hook Tooth

The hook tooth bandsaw blade has a pitch similar to the skip tooth, but cuts more aggressively because it has a 10゚ positive rake angle. When ripping and resawing, this blade has the least tendency to follow grain. While it sacrifices some smoothness of cut, the hook tooth is my favorite all-round blade.

Blade Pitch and Set

Teeth are set to one side or the other (left or right if you look straight at the front of teeth) in order to cut a kerf which is wide enough for the blade body to pass through without constantly binding. Blades for woodcutting applications are generally supplied with either an alternate set or a raker set. I like the raker set because every 3rd, 5th, or 7th tooth (depending on style and manufacturer) has no set to it. This raker tooth acts like a shovel to remove sawdust from the cut. Other sets are also available and can be experimented with for specific applications.

Choosing The Right Blade

There is not one miracle blade that will fulfill your every need on a consistent basis without serious trade-offs, though it is simple to choose the right blade with a little thought. Let's consider three important factors.

1. How tight of a curve is being cut, or is an accurate, straight cut important (e.g. ripping or resawing?

A lot of woodworking instruction books have charts showing the tightest radius that can be cut with a given size blade. I have found that these differ from book to book and are rarely a reliable indicator of how tight a curve a blade will actually cut. This is because blades with a greater set to the teeth make a wider kerf for the blade to turn in. The best thing to do is to first get an idea of the limits of each blade before getting stuck in the middle of a crucial cut. This can be done by taking a test cut in a piece of scrap stock. First, cut a straight line for about an inch and then start to turn the piece of wood as you feed forward. Increased the tightness of the curve until the back of the blade starts to rub against the opposite side of the kerf. At this point, if the curve is tightened further, the blade will start to bind and heat up. On some saws, the motor will start to labor. When this happens, the blade is being forced to cut too tight of a curve. Forcing a blade will not only give an inferior cut, but it can also cause premature blade breakage.

You will find that a wider blade (1/2") will cut a 3" to 4" diameter circle, whereas a 1/8" blade can cut about a 1/4" diameter circle. The best thing is to experiment so you develop a feeling for the approximate curve each size blade will cut. Of course, the use of different techniques such as using relief cuts, or cutting curves in successive passes can overcome the restrictions of a given blade. The blade-size range for most non-industrial bandsaws is about 1/8" to 3/4". Blades between 1/8" and 1/2" work best, and you should sample them to find out you for yourself what their limits are.

When a straight line is being cut, a wider blade usually works best. My choice for a general ripping blade is a 1/2" times 3 TPI hook tooth blade. This blade is wide enough to give a straight cut even in thick wood. On wood up to 3", 4" or thicker, even a 1/4" blade (with 6 TPI hook or skip) can give a very straight cut if the feed rate is slow and steady. If a lot of straight cutting is required, however, it is better to change to the wider blade for achieving more consistent results.

2. How thick and dense is the wood being cut?

The thickness and density of the wood being cut have a big effect on a blade's performance. As the size of the wood gets thicker, the blade has to move more sawdust from the cut before it can cut farther. The thickness of material and the type of cut dictate which to style and number of TPI are used. Generally, the thicker the wood, the fewer the TPI. A hook tooth and skip tooth pattern should be chosen. Let's look at several situations.

A blade cuts easier when it cuts across the grain. A good experiment is to first cut across the grain, then rotate the work piece so you are cutting with the grain (ripping). Notice the difference in the feed of the cut. If most of your cutting is cross-grain, you can get away with more TPI (up to say 14 TPI) even in thick wood.

Most of the time when cutting curves (which combines ripping and crosscutting) in stock 3" to 4" thick, it is best to switch to a 6" TPI hook. On thicker stock, or very dense stock use 3 TPI hook, which cuts more efficiently.

Thin woods 1/2" to 1" thick are best cut with blades of more TPI featuring a standard tooth style. I prefer these because they don't feed as fast as the hook or skip. However, if I'm in a hurry and don't need a smooth cut, I'll use a 6 TPI hook on 3/4" -thick wood. Choose the blade that feels most comfortable and gives the results you need.

The area that gives people the most trouble is resawing. This is when you stand the board on its edge and cut through its width - usually 3" to 12" (less than that is generally considered ripping). The blade that works best for resawing is the Wood Slicer variable hook tooth blade who's thin kerf 3-4 tpi design makes it the smoothest and quietest resaw blade on the market. Learn more about resawing with Wood Slicer Resaw Blade Results.

3. What kind of results are needed in the cut?

Many of the cuts made on a bandsaw are meant to remove excess stock so the piece can be completed using another process. Examples include cutting 1/8" outside the line before using a pattern jig on a shaper, or roughing out carving blocks or chair arms. In such cases, a coarser blade speeds up to work while still leaving a smooth enough cut to suit your needs.

However, there are times when a more finished cut is needed. Suppose for example you need to resaw material 4" thick but leave as smooth a cut as possible. By using a proper feed rate and being sensitive to the density of the wood, a much finer-toothed blade can be used successfully. What is important is that you as an operator understand both the possibilities and limitations of different blades.

Operator Technique

Sometimes you are forced to use the wrong blade because it's the only one you have. This happens to just about everyone occasionally. It may be possible to deal with such a situation by modifying your technique.

However, operator technique is also very important when using the correct blade. Good technique includes executing smooth turns (employing proper relief cuts were necessary) and more importantly, using the proper rate feed right. Avoid feeding material into the blade faster than the blade and cut it. When cutting curves, remember to maintain forward movement of the workpiece while turning.

What happens to it bandsaw blade as it cuts is quite different from what happens to a table saw blade, which is far more rigid. The bandsaw blade flexes in and arc away from the operator when it cuts. The top and bottom that are arc are defined by the upper and lower thrust bearings. This arc serves the purpose of absorbing the stress created by the act of sawing, distributing the stress over a greater distance. However, when the stress over however, when the blade receives too much feed pressure comet the art becomes more acute and, in effect stretching the back of the blade while buckling the front of the blade combo resulting in a boat cut.

In cases where a lot of feed pressure is exerted on the blade example re son, set the upper and lower thrust bearings to about 130 seconds behind the blade, allowing it to art backwards before contacting the thrust bearings. This produces 2 arcs 1 divide by upper and lower wheel and 1 defined by the upper and lower thrust bearings. The stress of cutting is distributed along a larger arc, permitting greater feed pressure.

One key to getting good results on a bandsaw is to developed a feel for the amount of feed pressure being exerted on the blade. This can only be accomplished by practicing while observing the results of your work. When changing feed rate, concentrate on doing it smoothly. Rapid changes in the feed rate (either faster or slower) can cause the blade to job to one side or the other.

Summary

So why is this article subtitled "The Bandsaw Balancing Act"? Simply this: In order to have success with your bandsaw, you must correctly balance machine alignment, blade choice, blade set up, and operator technique. For example, after you begin a cut, the blade heats up and stretches out, losing some of its tension. An alert operator will notice this, and either slow his feed rate to compensate, or turn off the machine and increase the tension. Either solution works, that if neither is done, the work piece can be ruined. Likewise, if the guides have not been properly set and operator doesn't take the time to adjust them, poor results will follow, even though the proper blade may have been selected.

Only by practicing, experimenting, and observing results can you developed a feel for balancing the variables which dictate a good cut in a given situation

How To Adjust or Tune A Bandsaw Blade The Bandsaw Balancing Act Part 1


Learn more about using, setting up and tuning Bandsaws:
Understanding Bandsaw Blades - Everything you need to know!
Are your bandsaw wheels coplanar?
What is the best Resaw technique: 3 Ways To Resaw

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Bandsaw Blades
New Complete Guide To Band Saws - Mark Duginske's highly recommended book on how to use bandsaws

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