First, let me say I do not claim to be a bandsaw blade expert but I am planning to share the conventional wisdom and personal experience I have gleened over the years. Feel free to point out where your experience or understanding of conventional wisdom differs from mine.
Cliff's Notes at the bottom by the way!
I have always loved bandsaws partly because they are so versatile and partly due to the fact that they are surrounded by as much mystery as science. Although, most bandsaw issues can be traced to a common logical cause there is still a level of black art associated with excellent results for even the most common usage. This extends, possibly even more so, to the blades. This may be the machine that is common in many hobby shops where there is the most confusion and contempt for the tooling it uses. With the table saw if we want to cut plywood we can just go to the Freud, Forrest et al catalog and pick out a blade that is listed for plywood or simply look on the package or blade, this extends to just about every cut and material we could make on a table saw. With bands for a bandsaw it becomes more difficult.
When we go to buy a bandsaw blade we have a myriad of factors to consider, length, width, backing gauge, kerf, set, type of teeth, material, pitch along with other qualities.
1. Length. The length of a blade is governed by the saw itself and will be listed on the saw or in the literature. By far the most common sizes are the 93 1/2" and 105" blades, the former is the standard size for a 14" cast clone without a riser and the later the same saw with a riser installed. You can vary a small amount on either side but it is best to stay with the suggested length (or if a range is given near the middle) since too long or short of a band can prevent you from properly tensioning the blade or even getting it on the saw.
2. Width. The width of the bandsaw blade is also a fairly easy specification to choose. There are three basic cuts that one will make on a bandsaw: resaw, rip and contour (I have left out specialized cuts like dovetails because everyone seems to have a different band that is their favorite if they do a lot of these). You will see as I go through the cuts there is a desire for wide blades, this is due to the fact that wider blades, properly tensioned, will have higher beam strengths and thus resist deflection better than thinner blades.
A. For resaw get the widest blade you saw can tension correctly. I have found that all but a very few steel spined saws will correctly tension the size blade the manufacturer says they will tension, the exceptions are the IMPORTED PM 14" steel spine and the Jet non-triangle steel spined saws, the former is not in production and the latter has been "cured" in current form with a redesigned triangular spine. For cast clones I do not recommend larger than a 1/2" .022 gauge or 5/8" .016 gauge blade. (gauge is important because thick blade takes more absolute pressure to reach the required PSI than a thin blade).
B. For ripping the same criteria apply, widest blade you can properly tension on your saw.
C. For contour cutting the optimum width is the widest blade that will still cut the tighest diameter contour your cut requires, still limited at the top by the tensioning ability of the saw and on the bottom by the minimum width the wheel/tire and the guides will allow, the minimum width can usually be reduced with accessories such as a Carter Stabilzer. I will list a basic diameter chart:
3/32" blade 1/8" D
1/8" blade 3/8" D
1/4" blade 1" D
1/2" blade 2 1/2" D
5/8" blade 3 3/4" D
3/4" blade 5 1/2" D
One last issue with blade width, besides being able to correctly tension a given width you also must be able to get the blade on and off of the saw, I have seen a couple of saws which it was difficult or near impossible to get the max width blade it was advertised to handle on and off without forcing or damaging the blade at some point in the ingress/egress path.
3. Blade material. Blades are also categorized by the type of material used for the backing/teeth or in the case of "carbide" blades the tooth material. The common types of blade materials encountered by woodworkers are, spring steel, silicon steel, carbon steel, bimetal and carbide tipped.
A. Spring steel teeth Rc 36-42. (A word about Rockwell Hardness, note that a 1 point increase on the scale doubles the abrasion resistence of the material). Spring steel is what the cheapo blades are made out of. It is unlikely that anyone reading this has any use for a spring steel blade. Very sharp initially, but the edge lasts about the time it takes to adjust the guides on the saw...
B. Spring steel with hardened teeth, teeth hardness Rc 48-50. These are most commonly encountered as thin kerf "resaw" blades. The Woodslicer (Highland Woodworking), Blade Runner (Iturra) and Kerfmaster (Spectrum Supply) are all examples of this type of blade. This blade came to us from the butcher industry. Be aware these blades have a very minimal kerf and thus should NOT be used for green wood nor will they cut contours well! It has three main benefits, it is very sharp to begin with, aiding low HP saws, the thin beam allows a given saw to tension a wider blade and with its minimal set and its thin gauge backing allows for a very thin kerf, saving wood from precious blanks. If you do not require one or more of the above listed benefits look elsewhere as these blades are false economy for you. Initially EXTREMELY sharp but dull faster then all but non-hardened spring steel.
C. Carbon steel, teeth hardness Rc 63-64. This is the standard workhorse of woodworking blades and produced in many configurations. They tend to be good inexpensive blades that are great to have in the configurations you use but not often since high usage blades are more economical if bought in Bimetal or carbide tipped. You may see them listed as flexback, this refers to the soft backing material made to reduce fatigue over smaller wheeled bandsaws. Be aware there are hardbacked blades as well BUT outside a production environment they are not needed and not desired unless your band is at a minamum 15' long, an example of this is the Lenox #32 Wood. Moderately sharp initially, dulls slower than silicon steel and faster than bi-metal.
D. Silicon or Swedish steel, teeth hardness Rc 60-61. This is a type of blade I avoid, it doesn't outlast carbon steel blades and the cost is usually significantly more and though it is initially very sharp it dulls quicker than carbon. At least one manufacturer claims the benefit of low tension but as I have said several times here I see no logical argument or proof shown that supports the low tension claim or the claims they make regarding the other benefits of low tension for their blade. YMMV. Initially, very sharp but dull quickly, faster than carbon.
E. Bimetal teeth Rc 65-66. Bimetal blades have a strip of HSS welded to, usually, a carbon back and results in a cost effective blade with very durable teeth who's backing is soft enough not to fatigue on small wheels. I would suggest if you actually USE your bandsaw and if you don't like to waste money every blade that you use often (except maybe your resaw blade) should be a bimetal blade if the configuration is manufactured in bimetal. Bimetal blades will outlast carbon blades 8-10 times and though "duller" initially than all but carbide blades they stay sharp longer than all but carbide blades. Be aware bimetal blades need more tension than a carbon steel blade 20,000-25,000 PSI versus 15,000, I often tension at or close to the next blade size up on the tension scale.
F. Carbide tipped blades Rc 68. These are blades with carbide teeth brazed onto backing material and can/should be sharpened to a very polished edge like a table saw blade. These blades though expensive are the kings of resaw and will outlast bimetal blades 3-4 times. They are initially the "dullest" of the types of blades I have discussed but will stay sharp enough to cut very well much longer than any of the others. Tension requirements are in the 25,000 PSI range and I generally tension them one size up on the saws scale. There are also brazed on stellite toothed blades, I am not aware of any current blade marketed for wood cutting that has stellite teeth, it is not quite as hard as carbide but more shock resistent. Also, be aware there are entire books written about the myriad types of carbide and its use in tooling but since the number of wood-centric carbide bandsaw blades is fairly small I have just used personal experience as opposed to researching the type of carbide each uses, plus manufacturers are often tight lipped about these things. Suffice it to say all the carbide BS blades I have used seem to wear at seemingly similar rates. I tend to look at these as resaw only blades BUT if one does a lot of ripping, particularly high silica content wood, they make excellent ripping blades and could be cost effective as well.
4. Gauge. Gauge is the thickness of the backing material and is the number you see in blade charts, usually from about .016-.050 for woodworking blades, often identified in the chart as thickness. It is important as it in part determines the beam strength as well as how much absolute force is needed to get the proper tension on the blade. The thicker the gauge the more likely it is to fatigue on smaller wheels. There are some guidelines as to which wheel sizes are "required" for certain gauges BUT as a Lenox tech told me "everyone breaks them" I won't bother. I will say for saws with smaller than 16" wheels IF you have a choice of backer gauge for a specific blade get the thinner material. Be aware that gauge is NOT kerf the kerf includes the set of the teeth, however in general terms the thicker the gauge the thicker the kerf though not 100%. I mention this because kerf is not given for many blades in the company literature.
5. Tooth set. First, understand there is an amount of set and a type of set. Teeth on all the blade materials I have discussed except carbide tipped are formed in one of several ways then bent outward to the left and right of the blade centerline, the outward bend determines the amount of set. This is the reason the kerf is wider than the backing material. Set is important as it reduces friction by ensuring the backing material doesn't contact the band in a straight cut and allows the backing material to pivot within the kerf in a contour cut. This is the reason a blade with minamal set (like the Woodslicer and its cousins) is a poor contour blade.
There are two basic TYPES of set associated with wood bandsaw blades, alternate and raker. In an alternate set every other tooth is bent out in the same direction away from the centerline, the other half of the teeth are bent the opposite direction away from the centerline. In a raker set some teeth are not bent outward but some are left in the center to "rake" waste out of the cut. In general you see raker sets in aggressive blades like hook and skip. The type of set is almost always listed in blade specs, the amount of set is less likely to be mentioned. Normally, if all the other specs say it is the correct blade for a particular use the amount of set will fit the bill.
6. Tooth shape or rake. Most bandsaw blades have either a 0 degree rake or a slight positive rake (around +5 degrees). To "see" rake think of a wave on the ocean, a 0 degree rake is when the tip top of the wave is straight up from the ocean surface, a positive rake is when the tip is starting to "break" over. The more positive rake the more agressive the blade, normally standard and skip blades have 0 degree rake, hook blades have positive rakes, usually around 5 degrees.
7. Tooth form. There are basically three types of tooth forms used in wood cutting bandsaw blades, standard, skip and hook (listed from least to most aggressive).
A. standard. The standard tooth blade has teeth evenly spaced close together, 0 degree rake and small gullets. These are best for small contours and any sort of cross grain cut and leave the smoothest finish of the three forms.
B. Skip. The skip tooth blade has teeth with the same shape/rake as standard but every other tooth missing, this leaves a larger gullet between the teeth, it is more aggressive than the standard blade.
C. Hook. The hook tooth blade adds a positive rake to a skip tooth blade. It is the most agressive of the three and has the largest gullets for ship removal. Best suited to heavy ripping and resawing. Leaves the roughest finish of the three.
8. Pitch. Pitch is the number of teeth per inch (TPI) of a blade. In general the more teeth the finer the cut, low TPI blades will cut quicker but not leave as fine a finish. The rule of thumb is no fewer then 3 teeth in the stock (so 1" stock should be cut with 3 TPI minimum and 3/4" stock a 4 TPI minimum etc). The lower the TPI generally the larger the gullets, so for softwoods I have found going one TPI down from what I would use in hardwood is useful even if it breaks the rule of thumb and if you are cutting extremely dense hardwoods going up one TPI can be of help since more teeth work better because there is not as much waste at a given feedrate as with softer material.
There are also variable pitch TPI blades, usually these are blades designed with resaw in mind, in woodworking. In tall resaw cuts blades tend to develop harmonic vibration, much like a guitar string, and variable pitch helps reduce that. Variable pitch blades usually have groups of 3-4 teeth in a row that have the same pitch and gullet depth, then change to a different pitch and gullet size for the next group of teeth. These blade are listed with the 2 pitchs that it contains such as 2-3 TPI or 1.3-3 TPI. There are high TPI variable pitch blades, many of which are designed for metal working, I personally have not seen enough benefit in wood cutting to be worth the extra money.
9. Blade prep and maintainence. When you first get a blade make sure the weld is straight and has been filed smooth, if it is not straight return the blade, if it is not smooth, either return it or gently file it smooth. When you install the blade for the first time, round the back of the blade with a stone while the saw is running. When you store the blade give it a thin coat of rust preventative. When a blade becomes dull replace it, don't push it you won't be happy with the results.
Cliff's notes:
There are a lot of different bandsaw blades and it is easy to feel like you need a different blade for every cut but I find you can do most of your cutting with 3-4 blades:
1. 1/2" 3 TPI Hook, if for a low HP 14" cast clone I would get a .022 gauge Woodslicer et al
2. 1/4" 6 TPI skip or hook
3. 1/8" 14 TPI standard
4. If you have a saw that can tension a bigger blade add a 4th blade, the biggest blade it will tension, hook, variable pitch in the range of 2-3TPI or 1.3-3 TPI (note the Lenox Woodmasters I mention below are NOT available in variable pitch smaller than 2" but they still do a great job in non-variable pitch)
For a cast clone I would get the 1/2" in a hardened spring steel as mentioned but the 1/4" in bimetal and the 1/8" in carbon. If you do a lot of resawing on a cast clone I would try a thin gauge 1/2" bimetal blade maybe a .025 4 TPI hook Lenox Diemaster 2.
For steel spined saws all the blades (except the 1/8") would be bimetal unless you want to spend the money on a carbide resaw blade.
Specific recomendations:
For smaller than 1/4" blades I like Starrett carbon
For 1/4"-1/2" general purpose I like the bimetal Lenox Diemaster 2
For 1/2-5/8" resaw blades I like the spring steel Kerfmaster, Woodslicer Bladerunner, again these are recommended for 14" cast clones
For 3/4" and up resaw blades I like four, the Lenox Woodmaster B (bimetal only in 1" and up), Lenox Woodmaster CT (carbide 1" and up), Lenox Trimaster (carbide 3/4" and up) and the Laguna Resaw King 3/4"-1 1/4". The Laguna has the benefit of being the only one that you can get resharpened.
Again, please point out where your opinion or your understanding differs and if you have additional info please post it. If you have questions about BS blades ask them, if I can't answer them I am sure someone here can!
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