diff --git a/MainWindowViewModel.cs b/MainWindowViewModel.cs
index 43cbec1..2a6ee9c 100644
--- a/MainWindowViewModel.cs
+++ b/MainWindowViewModel.cs
@@ -46,9 +46,16 @@ namespace DrillTools
         private const int SvsiEnsureVisible = 0x8;
         private const int SvsiFocused = 0x10;
         private const int SelectFileFlags = SvsiSelect | SvsiDeselectOthers | SvsiEnsureVisible | SvsiFocused;
-        private const double PpSourceDiameter = 3.203;
+        private static readonly double[] PpSourceDiameters = { 3.203, 4.503 };
         private const int PpSideCoordinateTolerance = 1500;
 
+        /// <summary>
+        /// PP 钻带来源孔径集合（3.203 PP 定位孔 / 4.503 铆钉孔）。
+        /// 比较使用容差 &lt; 0.001，与 <see cref="ToolItem.IsSpecialFixedDiameter"/> 同风格。
+        /// </summary>
+        private static bool IsPpSourceDiameter(double diameter)
+            => PpSourceDiameters.Any(d => Math.Abs(diameter - d) < 0.001);
+
         [DllImport("user32.dll")]
         private static extern bool SetForegroundWindow(IntPtr hWnd);
 
@@ -1226,7 +1233,7 @@ M30";
                 return null;
 
             var sourceTool = OriginalTools[OriginalTools.Count - 2];
-            if (Math.Abs(sourceTool.Diameter - PpSourceDiameter) >= 0.001)
+            if (!IsPpSourceDiameter(sourceTool.Diameter))
                 return null;
 
             if (sourceTool.TotalHoles != 3)
@@ -1249,7 +1256,7 @@ M30";
         private PpGenerationRule? GetOuterPpGenerationRule()
         {
             var sourceTool = OriginalTools.FirstOrDefault(tool =>
-                Math.Abs(tool.Diameter - PpSourceDiameter) < 0.001
+                IsPpSourceDiameter(tool.Diameter)
                 && (tool.TotalHoles == 13 || tool.TotalHoles == 15)
                 && tool.HoleLocations != null
                 && tool.HoleLocations.Count >= 4
@@ -1261,13 +1268,13 @@ M30";
         }
 
         /// <summary>
-        /// 从 3.203 外框孔中按右、上、左、下四边各取一个中位孔，并保持原钻带坐标文本。
+        /// 从 PP 来源孔径（3.203 PP 定位孔 / 4.503 铆钉孔）外框中按右、上、左、下四边各取一个中位孔，并保持原钻带坐标文本。
         /// </summary>
         private static List<string> SelectPpDrillTapeLocations(ToolItem sourceTool)
         {
             var points = ParsePpHolePoints(sourceTool.HoleLocations);
             if (points.Count < 4)
-                throw new InvalidOperationException("3.203 刀具坐标不足，无法生成 PP 钻带");
+                throw new InvalidOperationException("PP 来源孔径刀具坐标不足，无法生成 PP 钻带");
 
             int minX = points.Min(point => point.X);
             int maxX = points.Max(point => point.X);
@@ -1283,7 +1290,7 @@ M30";
             };
 
             if (selected.Any(point => point == null))
-                throw new InvalidOperationException("3.203 刀具未形成完整的上下左右四边孔位，无法生成 PP 钻带");
+                throw new InvalidOperationException("PP 来源孔径刀具未形成完整的上下左右四边孔位，无法生成 PP 钻带");
 
             var selectedTexts = selected
                 .Select(point => point!.Text)
@@ -1291,9 +1298,9 @@ M30";
                 .ToHashSet(StringComparer.Ordinal);
 
             if (selectedTexts.Count != 4)
-                throw new InvalidOperationException("3.203 刀具四边中位孔存在重复，无法生成 PP 钻带");
+                throw new InvalidOperationException("PP 来源孔径刀具四边中位孔存在重复，无法生成 PP 钻带");
 
-            // 输出顺序沿用原 3.203 刀具中的孔位顺序，避免改变已有钻带坐标排序习惯。
+            // 输出顺序沿用原 PP 来源孔径刀具（3.203/4.503）中的孔位顺序，避免改变已有钻带坐标排序习惯。
             return points
                 .Where(point => selectedTexts.Contains(point.Text))
                 .Select(point => point.Text)