Saw characteristics influencing efficiency in sawing steel?

  • #1
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Summary:
Cutting wires and band saws: Is it more efficient to saw steel by using a small diameter or large diameter cutting wire? Are large teeth better than smaller teeth?
Hello,

I am having a headache to try understand a possibly simple real-world problem: efficiency (as in number of strokes/cumulative length needed) to saw steel, assuming a constant sawing length per stroke and a known steel sectional area.

I began to think about the few assumptions I assume as true:
- saw material hardness must be greater than hardness of material to be sawn
- saw temperature must be within a certain range, otherwise a breakage may occur
- saw edge uneveness is what creates shear forces that make it possible to cut into the material
- edge uneveness and scale are important since if dust gets stuck in the edge, it would work as lubricant and decrease the friction between materials to the point that it can no longer cut due to lack on uneveness
- cutting edge thickness plays a role into time needed since I assume a thicker edge takes away more material per stroke

I am however not sure about some bits which lie their roots in (perhaps wrong) "common sense", such as:
- larger teeth cut away more material per stroke, so they are more efficient than smaller teeth
- lubrication is important to reduce wear on saw blade areas which are not actively shearing away material but are important to structural integrity of the saw blade and doubles as cooling (I however saw a video which used a circular saw blade and apparently disputed water lubrication and supported its use just as cooling agent and dust prevention measure)

The two types of saws I am interested into understanding about are diamond wire and band saws.
https://www.youtube.com/watch?v=wcS37A_jy0w
Assuming constant sawing length per stroke, same force applied and same steel sectional area (for scale and sake of simplicity, let's say 78.5 mm^2, as in a 10mm diameter bar), would it take less strokes (or could we say cumulative sawing length) to cut thru it using a diamond wire saw (assuming same edge uneveness in both) that's 0.2mm in diameter or 0.4mm in diameter?
I'd say the 0.2mm diameter wire would use less cumulative sawing length because it is removing less total steel volume in going thru those 78.5mm^2, though I am not sure if in real-world applications the 0.4mm diameter wire would be a better choice since it would wear less and be more reliable in terms of durability (as well as being able to withstand more force and thus be able to get pushed harder).

What about wire with the same diameter but different edge uneveness? Would the one with larger edge uneveness (either larger diamonds in a wire saw or larger teeth in a band saw) use less cumulative sawing length to cut thru?

I think that the ratio between material (to be cut) hardness, material (to be cut) cross sectional area and teeth size might be more important than simply teeth size (since I can easily picture too large teeth skipping on the material to be sawn with little material asportation), however I have no idea on how these could work.

I am not necessarily looking for an in-depth answer but more about debunking false myths and getting enough of an idea on how these variables come into play together.

Thank you
 

Answers and Replies

  • #2
gmax137
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Can you get a copy of Machinery's Handbook? It has a readable discussion on band saw blade selection. Pitch (or tooth count) is selected based on shape and size of the piece being cut. Speeds (blade feet per minute) and feeds (cutting rate, in^2 per minute) depend on blade pitch and material. The handbook has interesting graphs; these may also be available on the saw blade manufacturer's websites. Though the one I looked at has a "calculator" where you enter the parameters; the older style charts give a better visual representation of the overall ideas.
 
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  • #3
Baluncore
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I think you must separate the band saw discussion from the wire saw discussion as they are significantly different processes.

Wire sawing, where abrasive beads are swagged on a wire, requires there to be a curve in the wire so all beads are being pulled onto the surface being cut. Thicker wires can carry more tension and so can apply more cutting pressure than thin wires. The diameter of, and distance between beads will determine the minimum wire curvature, at which the wire between the beads will begin to wear on the steel yet to be cut.

The vertical curve in a bandsaw is very much less than in a wire saw. The gullet in front of a band saw tooth must carry swarf out of the cut without choking. A wire saw generates a fine powder that is removed in the fluid used to flush the cut.

What are the myths you think need to be debunked?
 

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