diff --git a/Lib/fontTools/varLib/instancer.py b/Lib/fontTools/varLib/instancer.py
index 570160e15..52d62c998 100644
--- a/Lib/fontTools/varLib/instancer.py
+++ b/Lib/fontTools/varLib/instancer.py
@@ -752,37 +752,6 @@ def setMacOverlapFlags(glyfTable):
             glyph.flags[0] |= flagOverlapSimple
 
 
-def setDefaultWeightWidthSlant(ttFont, location):
-    if "wght" in location and "OS/2" in ttFont:
-        weightClass = otRound(max(1, min(location["wght"], 1000)))
-        log.info("Setting OS/2.usWidthClass = %s", weightClass)
-        ttFont["OS/2"].usWeightClass = weightClass
-
-    if "wdth" in location:
-        # map 'wdth' axis (1..200) to OS/2.usWidthClass (1..9), rounding to closest
-        steps = [50.0, 62.5, 75.0, 87.5, 100.0, 112.5, 125.0, 150.0, 200.0]
-        n = len(steps)
-        os2WidthClasses = {
-            (prev + curr) / 2: widthClass
-            for widthClass, (prev, curr) in enumerate(
-                zip(islice(steps, 0, n - 1), islice(steps, 1, n)), start=1
-            )
-        }
-        wdth = location["wdth"]
-        for percent, widthClass in sorted(os2WidthClasses.items()):
-            if wdth < percent:
-                break
-        else:
-            widthClass = 9
-        log.info("Setting OS/2.usWidthClass = %s", widthClass)
-        ttFont["OS/2"].usWidthClass = widthClass
-
-    if "slnt" in location and "post" in ttFont:
-        italicAngle = max(-90, min(location["slnt"], 90))
-        log.info("Setting post.italicAngle = %s", italicAngle)
-        ttFont["post"].italicAngle = italicAngle
-
-
 def normalize(value, triple, avarMapping):
     value = normalizeValue(value, triple)
     if avarMapping:
@@ -919,7 +888,7 @@ def instantiateVariableFont(
         if "glyf" in varfont and overlap:
             setMacOverlapFlags(varfont["glyf"])
 
-    setDefaultWeightWidthSlant(
+    varLib.set_default_weight_width_slant(
         varfont,
         location={
             axisTag: limit
diff --git a/Tests/varLib/instancer_test.py b/Tests/varLib/instancer_test.py
index 5cb604e40..7c587b595 100644
--- a/Tests/varLib/instancer_test.py
+++ b/Tests/varLib/instancer_test.py
@@ -1072,79 +1072,6 @@ def test_setMacOverlapFlags():
     assert b.components[0].flags & flagOverlapCompound != 0
 
 
-@pytest.fixture
-def ttFont():
-    f = ttLib.TTFont()
-    f["OS/2"] = ttLib.newTable("OS/2")
-    f["post"] = ttLib.newTable("post")
-    return f
-
-
-class SetDefaultWeightWidthSlantTest(object):
-    @pytest.mark.parametrize(
-        "location, expected",
-        [
-            ({"wght": 0}, 1),
-            ({"wght": 1}, 1),
-            ({"wght": 100}, 100),
-            ({"wght": 1000}, 1000),
-            ({"wght": 1001}, 1000),
-        ],
-    )
-    def test_wght(self, ttFont, location, expected):
-        instancer.setDefaultWeightWidthSlant(ttFont, location)
-
-        assert ttFont["OS/2"].usWeightClass == expected
-
-    @pytest.mark.parametrize(
-        "location, expected",
-        [
-            ({"wdth": 0}, 1),
-            ({"wdth": 56}, 1),
-            ({"wdth": 57}, 2),
-            ({"wdth": 62.5}, 2),
-            ({"wdth": 75}, 3),
-            ({"wdth": 87.5}, 4),
-            ({"wdth": 100}, 5),
-            ({"wdth": 112.5}, 6),
-            ({"wdth": 125}, 7),
-            ({"wdth": 150}, 8),
-            ({"wdth": 200}, 9),
-            ({"wdth": 201}, 9),
-            ({"wdth": 1000}, 9),
-        ],
-    )
-    def test_wdth(self, ttFont, location, expected):
-        instancer.setDefaultWeightWidthSlant(ttFont, location)
-
-        assert ttFont["OS/2"].usWidthClass == expected
-
-    @pytest.mark.parametrize(
-        "location, expected",
-        [
-            ({"slnt": -91}, -90),
-            ({"slnt": -90}, -90),
-            ({"slnt": 0}, 0),
-            ({"slnt": 11.5}, 11.5),
-            ({"slnt": 90}, 90),
-            ({"slnt": 91}, 90),
-        ],
-    )
-    def test_slnt(self, ttFont, location, expected):
-        instancer.setDefaultWeightWidthSlant(ttFont, location)
-
-        assert ttFont["post"].italicAngle == expected
-
-    def test_all(self, ttFont):
-        instancer.setDefaultWeightWidthSlant(
-            ttFont, {"wght": 500, "wdth": 150, "slnt": -12.0}
-        )
-
-        assert ttFont["OS/2"].usWeightClass == 500
-        assert ttFont["OS/2"].usWidthClass == 8
-        assert ttFont["post"].italicAngle == -12.0
-
-
 def _strip_ttLibVersion(string):
     return re.sub(' ttLibVersion=".*"', "", string)