diff --git a/CHANGELOG.md b/CHANGELOG.md
index 61fadf85..bb2ad8f0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,12 @@ CHANGELOG for FlatCAM beta
 
 =================================================
 
+25.08.2021
+
+- fixed some issues in the convert_units
+- added a new GUI element, a radio button that can change a setting in the self.defaults preferences dict
+- made sure that the update of the default properties tab (in the Notebook) is done only for certain keys in self.defaults not for all
+
 24.08.2021
 
 - using PyQt6 with multi monitors, when the pixel ratio (scaling in WIndows) is different than 1.0 there are visual issues in the 3D canvas - trying to solve by updating the dpi - partial solve
diff --git a/appGUI/GUIElements.py b/appGUI/GUIElements.py
index cbf1f5f3..3240f455 100644
--- a/appGUI/GUIElements.py
+++ b/appGUI/GUIElements.py
@@ -109,6 +109,40 @@ class RadioSet(QtWidgets.QWidget):
                 option['radio'].setDisabled(val)
 
 
+class RadioSetDefaults(RadioSet):
+
+    def __init__(self, choices, dictionary=None, key_spec=None, orientation='horizontal', stretch=None, parent=None):
+        """
+        When a choice is made then the selected value is set in the key key_spec from the dictionary 'dictionary'
+        The choices are specified as a list of dictionaries containing:
+
+        * 'label': Shown in the UI
+        * 'value': The value returned is selected
+
+        :param choices: List of choices. See description.
+        :param orientation: 'horizontal' (default) of 'vertical'.
+        :param parent: Qt parent widget.
+        :type choices:      list
+        :param dictionary:
+        :type dictionary:   "dict"
+        :param key_spec:
+        :type key_spec:      'str'
+        """
+
+        super(RadioSetDefaults, self).__init__(choices=choices, orientation=orientation, stretch=stretch, parent=parent)
+        self.dictionary = dictionary
+        self.key_spec = key_spec
+
+    def on_toggle(self, checked):
+        if checked:
+            self.group_toggle_fn()
+            ret_val = str(self.get_value())
+            if self.dictionary is not None and self.key_spec is not None:
+                self.dictionary[self.key_spec] = ret_val
+            self.activated_custom.emit(ret_val)
+        return
+
+
 # class RadioGroupChoice(QtWidgets.QWidget):
 #     def __init__(self, label_1, label_2, to_check, hide_list, show_list, parent=None):
 #         """
diff --git a/appGUI/preferences/general/GeneralAppPrefGroupUI.py b/appGUI/preferences/general/GeneralAppPrefGroupUI.py
index d4fca850..cbef327f 100644
--- a/appGUI/preferences/general/GeneralAppPrefGroupUI.py
+++ b/appGUI/preferences/general/GeneralAppPrefGroupUI.py
@@ -4,7 +4,7 @@ from PyQt6 import QtWidgets
 from PyQt6.QtCore import QSettings
 
 from appGUI.GUIElements import RadioSet, FCSpinner, FCCheckBox, FCComboBox, FCButton, OptionalInputSection, \
-    FCDoubleSpinner, FCLabel, FCGridLayout
+    FCDoubleSpinner, FCLabel, FCGridLayout, RadioSetDefaults
 from appGUI.preferences.OptionsGroupUI import OptionsGroupUI
 
 import gettext
@@ -35,8 +35,9 @@ class GeneralAppPrefGroupUI(OptionsGroupUI):
         self.unitslabel.setToolTip(_("The default value for the application units.\n"
                                      "Whatever is selected here is set every time\n"
                                      "FlatCAM is started."))
-        self.units_radio = RadioSet([{'label': _('MM'), 'value': 'MM'},
-                                     {'label': _('IN'), 'value': 'IN'}])
+        self.units_radio = RadioSetDefaults(
+            choices=[{'label': _('MM'), 'value': 'MM'}, {'label': _('IN'), 'value': 'IN'}]
+        )
 
         grid0.addWidget(self.unitslabel, 0, 0)
         grid0.addWidget(self.units_radio, 0, 1)
diff --git a/app_Main.py b/app_Main.py
index c89eddda..1f34bd9a 100644
--- a/app_Main.py
+++ b/app_Main.py
@@ -1396,7 +1396,7 @@ class App(QtCore.QObject):
         self.file_saved.connect(lambda kind, filename: self.register_save_folder(filename))
 
         # when the defaults dictionary values change
-        self.defaults.defaults.set_change_callback(callback=self.on_properties_tab_click)
+        self.defaults.defaults.set_change_callback(callback=self.on_defaults_value_changed)
 
         # ###########################################################################################################
         # ########################################## Standard signals ###############################################
@@ -1806,6 +1806,18 @@ class App(QtCore.QObject):
     def log_path(self):
         return os.path.join(self.data_path, 'log.txt')
 
+    def on_defaults_value_changed(self, key_changed):
+        # when changing those properties the associated keys change so we get an updated Properties default Tab
+        if key_changed in [
+            "global_grid_lines", "global_grid_snap", "global_axis", "global_workspace", "global_workspaceT",
+            "global_workspace_orientation", "global_hud"
+        ]:
+            self.on_properties_tab_click(index=None)
+
+        # TODO handle changing the units in the Preferences
+        # if key_changed == "units":
+        #     self.on_toggle_units(no_pref=False)
+
     def on_app_restart(self):
 
         # make sure that the Sys Tray icon is hidden before restart otherwise it will
@@ -4600,7 +4612,7 @@ class App(QtCore.QObject):
             if dim in ['tools_mill_tooldia', 'tools_ncc_tools', 'tools_solderpaste_tools', 'tools_iso_tooldia',
                        'tools_paint_tooldia', 'tools_transform_ref_point', 'tools_cal_toolchange_xy',
                        'gerber_editor_newdim', 'tools_drill_toolchangexy', 'tools_drill_endxy',
-                       'geometry_toolchangexy', 'geometry_endxy', 'tools_solderpaste_xy_toolchange']:
+                       'tools_mill_toolchangexy', 'tools_mill_endxy', 'tools_solderpaste_xy_toolchange']:
                 if not self.defaults[dim] or self.defaults[dim] == '':
                     continue
 
@@ -4672,6 +4684,8 @@ class App(QtCore.QObject):
             self.log.debug("on_toggle_units(): Same as previous, ignoring.")
             return
 
+        # new_units = self.defaults["units"]
+
         # Keys in self.defaults for which to scale their values
         dimensions = [
             # Global
@@ -4693,15 +4707,15 @@ class App(QtCore.QObject):
             "excellon_editor_slot_length",
 
             # Geometry Object
-            'geometry_cutz', "geometry_depthperpass", 'geometry_travelz', 'geometry_feedrate',
-            'geometry_feedrate_rapid', "geometry_toolchangez", "geometry_feedrate_z",
-            "geometry_toolchangexy", 'tools_mill_tooldia', 'geometry_endz', 'geometry_endxy',
-            "geometry_extracut_length", "geometry_z_pdepth",
-            "geometry_feedrate_probe", "geometry_startz", "geometry_segx", "geometry_segy", "geometry_area_overz",
+            'tools_mill_cutz', "tools_mill_depthperpass", 'tools_mill_travelz', 'tools_mill_feedrate',
+            'tools_mill_feedrate_rapid', "tools_mill_toolchangez", "tools_mill_feedrate_z",
+            "tools_mill_toolchangexy", 'tools_mill_tooldia', 'tools_mill_endz', 'tools_mill_endxy',
+            "tools_mill_extracut_length", "tools_mill_z_pdepth",
+            "tools_mill_feedrate_probe", "tools_mill_startz", "geometry_segx", "geometry_segy", "tools_mill_area_overz",
 
             # CNCJob Object
-            'cncjob_tooldia', "cncjob_al_travelz", "cncjob_al_probe_depth", "cncjob_al_grbl_jog_step",
-            "cncjob_al_grbl_jog_fr", "cncjob_al_grbl_travelz",
+            'cncjob_tooldia', "tools_al_travelz", "tools_al_probe_depth", "tools_al_grbl_jog_step",
+            "tools_al_grbl_jog_fr", "tools_al_grbl_travelz",
 
             # Isolation Tool
             "tools_iso_tool_cutz",