## 2 Materials and Methods
### Variable Engineered Micro-Geometry of the Cutting Edges of Saws  
For the conventional circular saw, following the brazing operations, the carbide tips of each saw were ground (Vollmer) at the manufacturer. The polycrystalline diamond grit sizes of the grinding wheels were 280 and 180 for the rake face and sides of the tips, respectively. The clearance face was ground with a polycrystalline diamond wheel with a dual grit combination 150/320. Therefore, after grinding all faces, the cutting edge of the tips is defined as having an up-sharp profile. It should be noted that for the conventional saws with up-sharp tips, coating was deposited on the tips after the grinding of their cutting edges.  
Two coated and two uncoated conventional saws had the geometry of their carbide tips modified. The purpose was to change the profile of the cutting edges of all their carbide tips. The new profile was achieved by honing the cutting edge of each tip using brushes made of abrasive bristles of nylon loaded with micrometric natural diamond particles. The geometry of the modified cutting edges followed a waterfall home profile (K = 2) with Sy = 20 \(\upmu\)m and S\(\alpha\) = 10 \(\upmu\)m, as exemplified in Figure 3. The microgeometry of this profile  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Saw body material & AISI 8670 \\ \hline Tip material & 88\% WC and 12\% Co \\ \hline Number of tips & 42 \\ \hline Saw diameter (mm) & 610 \\ \hline Saw thickness (mm) & 2.79 \\ \hline kerf width (mm) & 3.91 \\ \hline Wedge angle & 56.3\({}^{\circ}\) \\ \hline Rake angle & 24.7\({}^{\circ}\) \\ \hline Top clearance angle & 9\({}^{\circ}\) \\ \hline Radial clearance angle (left and right) & 1\({}^{\circ}\) \\ \hline Left side clearance (mm) & 0.56 \\ \hline Right side clearance (mm) & 0.58 \\ \hline Supplier of the saws: Haskin Industrial Co., North Bay, ON, Canada. \\ \hline \hline \end{tabular}
\end{table}
Table 2: Circular saw specifications.  
was chosen based on previous work carried out internally at Conicity Technology, Turtle Creek, PA, USA [23].  
It is well established that the thickness of the uncut chip changes from a maximum, which is equal to the feed per tooth, to a negligible amount on the tool's corner radius according to Figure 4 [5]. In other words, the ratio of uncut chip thickness to the edge radius varies along the corner radius. In the cutting process, the ultimate goal is to keep the material removal process as efficient as possible [5]. As a result, the size of edge preparation must change along the corner radius.  
Figure 3: Schematic representation of the (**a**) up-sharp cutting edge of a WC-Co tip at Haskin Industrial Co. and (**b**) modified cutting edge of a WC-Co tip after honing to generate a waterfall home profile at Conicity Technology.  
Figure 2: (**a**) Set-up of saws at the chamber of PVD coating system, (**b**) Coated zone on a circular saw.  
To maintain a specific ratio of edge preparation size to the thickness of the uncut chip, edge preparation was distributed along the corner radius of the tip. Therefore, the edge preparation on the section of the cutting edge that transitions around the corner radius varied in size. The modification varied between 20 \(\upmu\)m on the primary cutting edge to 4 \(\upmu\)m on its flank side edges. It is well known that uneven kerf width or side clearance of the circular saw tips results in saw vibration [24]. Therefore, all the tips of circular saws were characterized using a video tooth inspector apparatus (developed by FPI Innovations, Quebec City, QC, Canada) before performing the initial test. The average kerf width and average side clearances of the tips were measured to assure that these values were in accordance with the specifications reported by the saw manufacturer. The average kerf and average side clearances were 3.9100 mm (\(\pm\)0.0002) and 0.5588 mm (\(\pm\)0.0004), respectively for all saws.