Saw Blade Types
Re-grindable (Resharpenable) Carbide-Tipped Saw Blades
The first carbide-tipped saw blades had carbide tips brazed to the circular blade body. The brazing compound was silver based and bonded at high temperatures of about 1380 degrees Fahrenheit (750 degrees Celsius). (see the History of Carbide Sawing article on Sawing Academy).
This method is still used for re-grindable, carbide-tipped circular saw blades, but has been improved over the last 50 years. Today, copper shims are used between the carbide tips and the body of the saw blade to dampen the impact when the carbide teeth engage the metal. The shims also take care of different thermal expansion coefficients between the carbide tip and the steel body. The flux and silver brazing material that guarantee a solid connection was also improved.
One Way (Throwaway) Blades
One way (throwaway) blades are available up to 36” (914 mm) diameter and used for general purpose sawing. Larger diameter blade bodies are too expensive to be thrown away after one use.
The invention of hard coating carbide tips extended the tool life due to their wear resistance to the cutting edges. They are also great for cutting stainless steel, because their coating prevents the welding of the chips to the carbide tip. Presently, these blades cannot be cost-effectively resharpened because of the hard coating, and they are discarded after one use.
Small diameter and thin blade bodies are relatively practical, and the cost is absorbed by the higher tool life of the coated carbide tips. These one way saw blades have replaced the re-grindable blades of the smaller sizes. Another advantage is the reduced material waste--the saw blades can be thinner because they don’t have to be reground, and the fatigue life doesn’t have to extend for a longer period time.
Replaceable Carbide Tip Circular Saw Blades
The experience of replaceable tip slotting cutters for milling, and the advantage of using already hard coated carbide tips, inspired manufacturers to use this technology on larger circular saw blades. It is now possible to replace the tips yourself and eliminate the transport and re-grinding costs.
However, not every saw machine is capable of using expensive blades. The machine must have a rigid design with sensors that can detect tooth breaks and wear and tear.
Replaceable carbide tip blades are expensive because the blade body requires precision machining of the carbide tip seats. If the carbide seats are damaged, they can be hard to fix the blade body may have to be discarded. Up to now, the market share of replaceable tip saw blades was small.
Cost Comparison of Blade Types
An accurate comparison of cost depends on many factors: Is cutting rate more important than tool life; is transportation to and from blade repair shops an issue, etc.?
If the blades are professionally handled, regrindable blades can be re-sharpened about eight times and retipped 4 times before the blade body gets fatigued or is worn beyond repair. That is eight times regrinding the new blade, plus 8x4 regrinds for each time when the blade is retipped, for a total of 40 regrinds for the life of a blade. On average, five tips must be replaced for each regrind.
Approximate Cost of Re-grindable (Resharpenable) Carbide-Tipped Saw Blades
24” Diameter, 60 teeth saw blade:
|The cost of a new blade at 24” (610 mm) x 60 teeth||$ 390.00|
|4 times retipping 60 teeth = 240 tips at $3.50/tip||$ 840.00|
40 x 5 teeth replacement = 200 tips at $5.35/tip
|40 times regrinding at $54||$ 2,160.00|
| Retensioning and other general maintenance at each regrind process
40 x $10/blade (approximate cost $10 per regrind)
| Total Cost for a blade
(Assuming free shipment by the blade repair shop)
|Average tool life 15,000 sq. in. (9.7 m2)/blade for one usage.
Total tool life for the life of a blade = 15,000 x 40= 600,000 sq. in. (384.6 m2)
Average Cost per square inch of cut for 24” – 60 teeth resharpenable saw blade ($4,860/600,000) =
Approximate Cost of One Way blades
A one way 24” (610 mm) diameter saw blade has less chip load per tooth, therefore it will have more teeth (about 80) to get a better performance. The gullet size also shrinks, and chip breakers are used to avoid problems with jamming. More teeth and a smaller chip load result in a better surface finish and less burr.
|Approx. Cost of a 24” - 80 Tip 0.12’’ (3 mm) kerf (tooth width) blade||$ 461.00|
| Tool life is much higher due to the coating, and is about 50,000 sq. in. (32 m2)
The cost per square inch is ($461/50,000) =
| $.009/sq. in.
Although the basic cost for a one way blade is more expensive, the convenience of easy handling justifies the higher cost. The cost advantage with smaller diameters is in favor of one-way blades.
Approximate Cost of Replaceable Carbide-Tipped Circular Saw Blades
Replaceable carbide-tipped, circular saw blades are generally more expensive. The best justifications for these types of saw blades are the savings of shipping and handling costs, and the higher tool life due to the coated teeth.
Smaller sizes with replaceable teeth and 24” diameter 60-teeth saw blades are too expensive for most applications because of the blade body and material waste due from the wider kerf. Thus, it is very important to monitor the wear of the carbide teeth and avoid damage when possible.
The diagram below shows tool life and power consumption based on tool wear:
With a new blade, the sharp edges wear more quickly at the first cuts, but later the wear of the teeth becomes more gradual. If one tooth breaks, the next one has to take a double load. If the second tooth breaks, it’s a domino effect: They will break in sequence and will destroy the tooth seats, thus destroying the blade body.
While every aspect points to the advantage of replaceable tipped blades, the key is the proper maintenance. This type of blade could be the most cost efficient if it can be sufficiently protected from damages beyond normal wear.
The above is basic information for quick comparisons. If you really want the best solution more information is needed:
- What machines are available (HP, RPM, Stiffness, etc.)?
- How experienced is the saw operator?
- What material will be cut (chemical composition, hardness, shape, etc.)?
- What are the stock sizes and length?
- Quantity of cuts, per day, per week; and number of shifts?
- Is the shop location close to a good blade repair shop?
- What are the shop environments (quality of operation, maintenance, etc.)?
- What is the highest cutting rate?
- What is the lowest cost?
- Is the machine fully automatic?
- Unattended operation?
- Operator controlled production?
- Material loss due to Kerf?
- Is a new saw needed?
An in depth discussion with a saw expert will give you the best answer!
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