diff --git a/Makefile b/Makefile
index 8c389d1..63c7c13 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,7 @@ design: clean
 	cat design/PCO_thread.csv | awk -f design/PCO_thread.awk >> design/THREAD_TABLE.csv
 	cat design/UIS_thread.csv | awk -f design/UIS_thread.awk >> design/THREAD_TABLE.csv
 	cat design/microscope_thread.csv | awk -f design/microscope_thread.awk >> design/THREAD_TABLE.csv
+	cat design/GPI_thread.csv | awk -f design/GPI_thread.awk >> design/THREAD_TABLE.csv
 	cat design/THREAD_TABLE.csv | awk -f design/autogenerate.awk > THREAD_TABLE.scad
 
 .PHONY: test
diff --git a/THREAD_TABLE.scad b/THREAD_TABLE.scad
index 7629b9f..4b2547a 100644
--- a/THREAD_TABLE.scad
+++ b/THREAD_TABLE.scad
@@ -1901,4 +1901,8 @@ THREAD_TABLE = [["G1/16-ext", [0.907, 3.1631, 6.3625, [[0, -0.4252], [0, 0.4252]
 ["32-UN-13/16-int", [0.79375, -10.3492, 20.6914, [[0, 0.3473], [0, -0.3473], [0.4296, -0.0992], [0.4296, 0.0992]]]],
 ["RMS-ext", [0.7056, 9.5829, 19.1859, [[0.0, -0.3274], [0.0, 0.3273], [0.4932, 0.0706], [0.4932, -0.0706]]]],
 ["RMS-int", [0.7055, -10.3042, 20.5085, [[0.0, 0.2630], [0.0, -0.2630], [0.4808, -0.0127], [0.4808, 0.0127]]]],
+["GPI-33-ext", [4.233, 14.72,  29.44 , [[  0,  -1.20], [0,  1.20], [ 1.20,  0.60], [1.20, -0.60]]]],
+["GPI-33-int", [4.233, -16.455,  32.91 , [[ 0,  1.20  ], [0,  -1.20], [1.20, -0.60], [1.20, 0.60]]]],
+["GPI-63-ext", [4.233, 29.72,  59.44 , [[  0,  -1.20], [0,  1.20], [ 1.20,  0.60], [1.20, -0.60]]]],
+["GPI-63-int", [4.233, -31.955,  63.91 , [[ 0,  1.20  ], [0,  -1.20], [1.20, -0.60], [1.20, 0.60]]]],
 ];
diff --git a/design/GPI_thread.awk b/design/GPI_thread.awk
new file mode 100644
index 0000000..3536b9d
--- /dev/null
+++ b/design/GPI_thread.awk
@@ -0,0 +1,4 @@
+/^[^#]/ {
+	print $0;
+}
+
diff --git a/design/GPI_thread.csv b/design/GPI_thread.csv
new file mode 100644
index 0000000..1eaf54c
--- /dev/null
+++ b/design/GPI_thread.csv
@@ -0,0 +1,5 @@
+# Designator,Pitch,Rrot,Dsupport,r0,z0,r1,z1,r2,z2,r3,z3
+GPI-33-ext,4.233,14.72, 29.44 ,  0, -1.20,0, 1.20, 1.20, 0.60,1.20,-0.60
+GPI-33-int,4.233,-16.455, 32.91 , 0, 1.20  ,0, -1.20,1.20,-0.60,1.20,0.60
+GPI-63-ext,4.233,29.72, 59.44 ,  0, -1.20,0, 1.20, 1.20, 0.60,1.20,-0.60
+GPI-63-int,4.233,-31.955, 63.91 , 0, 1.20  ,0, -1.20,1.20,-0.60,1.20,0.60
\ No newline at end of file
diff --git a/tests/test_table.awk b/tests/test_table.awk
index 3757c40..0598ed3 100644
--- a/tests/test_table.awk
+++ b/tests/test_table.awk
@@ -107,8 +107,40 @@ BEGIN	{
 	NR_OF_TESTS += 2;
 }
 
-/(G.+-ext)|(RMS-ext)/ { 
-	# ext G- and RMS threads have +/-62.5 deg slopes, horizontal crest / valley
+/GPI-.+-ext/ { 
+	# ext GPI threads have  +/-63.4349 deg slopes, horizontal crest / valley
+	parse();
+	m1 = slope(v0, v3) / deg;
+	m2 = slope(v2, v1) / deg;
+	if (m1 > 63.4349 + dphi || m1 < 63.4349 - dphi \
+	    || m2 < -63.4349 - dphi || m2 > -63.4349 + dphi) {
+		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
+	test_horizontal();
+	tested = 1;
+	NR_OF_TESTS += 2;
+}
+
+# Todo - Fix this angle test for GPI
+/GPI-.+-int/ { 
+	# int GPI threads have +/-63.4349 deg slopes, horizontal crest / valley
+	parse();
+	m1 = slope(v3, v0) / deg;
+	m2 = slope(v1, v2) / deg;
+	if (m1 > -63.4349 + dphi || m1 < -63.4349 - dphi \
+	    || m2 < 63.4349 - dphi || m2 > 63.4349 + dphi) {
+		print designator " FAIL: " m1 ", " m2 " deg";
+		PASS = 0;
+	}
+	test_horizontal();
+	tested = 1;
+	NR_OF_TESTS += 2;
+}
+
+
+/G[^A-Z]+-ext|(RMS-ext)/ { 
+	# ext M threads have +/-62.5 deg slopes, horizontal crest / valley
 	parse();
 	m1 = slope(v0, v3) / deg;
 	m2 = slope(v2, v1) / deg;
@@ -122,7 +154,7 @@ BEGIN	{
 	NR_OF_TESTS += 2;
 }
 	
-/(G.+-int)|(RMS-int)/ { 
+/(G[^A-Z]+-int)|(RMS-int)/ { 
 	# int G- and RMS threads have +/-62.5 deg slopes, horizontal crest / valley
 	parse();
 	m1 = slope(v3, v0) / deg;