Drawing Surface Finish and GD&T Symbols

Make Drawing can put surface finish symbols and GD&T tolerance frames on the sheet. A surface finish symbol says how smooth a surface must be (its Ra value), whether it must be machined, which way the tool marks run (the lay) and how much material to leave for machining. A tolerance frame (a feature control frame) gives one of the 14 geometric tolerances, its size and up to three datums. Each one points at an edge of a view, or at the true length of a broken view, with a leader ending in an arrow. All of it goes into the DXF with the views.

What you get: surface finish symbols and GD&T tolerance frames on the drawing sheet, each with a leader to the edge you pick, and in the DXF on their own layers (FINISH and GDT).

Step by Step

1. Open a part and show the bodies you want on the drawing.
2. Click the Documents tab, then Make Drawing. Set the sheet, the scale and the views as usual (see Make Drawing).
3. At the bottom of the left side of the window, click Advanced options to open it, then turn on Advanced (GD&T, surface finish), the box under the notes settings. It starts off, so the section is hidden until you tick it. Your choice is remembered in this browser. If the drawing already holds a symbol or a frame, the section is shown and the box stays ticked.
4. Under Surface finish and tolerance frames, click Add surface finish or Add tolerance frame. Each one gets its own box, named Symbol 1, Symbol 2 and so on.
5. Fill in its boxes (see Options below).
6. In Attach to, pick the view it points into, then pick the edge in Edge. The edges are listed longest first, with their length and whether they are level, upright or at an angle.
7. Check the preview. The line under it counts the symbols and frames. When something is wrong it says why, naming the symbol, and Download DXF is greyed out.
8. Click Remove in a symbol's box to take it away. Click Download DXF when it looks right.

Options

Surface finish

• Ra: the roughness average, in micrometers (µm) when your display unit is metric, or microinches (µin) when it is inches. It starts at 3.2 µm (125 µin). From 0.005 to 100 µm, or 0.2 to 4000 µin. Leave it empty for no value. On the sheet it is written as Ra and the number, in µm on a millimeter sheet and in µin on an inch sheet.
• Process: Any process (the plain check mark), Machining required (a bar closes the check mark) or No machining allowed (a circle in the check mark). It starts on Machining required.
• Lay: the way the tool marks run: None, = Parallel or Perpendicular (to the line the symbol points at), X Crossed, M Many directions, C Circular, R Radial or P Pits or bumps. It starts on None.
• Allowance: how much material to leave for machining, in your display unit, written left of the symbol. Leave it empty for none.
• A symbol with no Ra, Any process, no lay and no allowance says nothing, so it is refused.

Tolerance frame

• Characteristic: one of the 14: Straightness, Flatness, Circularity (roundness), Cylindricity, Profile of a line, Profile of a surface, Angularity, Perpendicularity, Parallelism, Position, Concentricity, Symmetry, Circular runout and Total runout. It starts on Position. Each is drawn with lines and circles, so it shows in any CAD program.
• Diameter (a round zone): puts the diameter sign before the tolerance. It goes only with Straightness, Angularity, Perpendicularity, Parallelism, Position and Concentricity. It starts ticked for Position; picking another characteristic unticks it.
• Tolerance: the size of the tolerance zone, in your display unit (you can also type mm or in after the number). It starts at 0.1 mm (0.005 in). More than 0 and at most 25 mm, or at most 1 in when your display unit is inches. The allowance has the same limit. On the sheet it is written in the sheet's unit, with at most 3 decimals of a millimeter or 4 decimals of an inch.
• Modifier: None, M (most material) or L (least material), drawn as a circled M or L after the tolerance. It starts on None.
• Datum 1, Datum 2, Datum 3: the primary, secondary and tertiary datum letters (A to Z, without I, O and Q), each with its own modifier. Datum 1 starts on A, the others on None. Fill them in order, and use each letter once.
• Flatness, Straightness, Circularity and Cylindricity take no datum, so picking one of them sets the datums to None. Angularity, Perpendicularity, Parallelism, Concentricity, Symmetry and both runouts need at least one. Position and the two profiles may have datums or not.

Where it points

• Attach to: Front view, Top view, Right view, Isometric view, Section view, Auxiliary view, Detail view or True length dimension. It starts on Front view. The view must be on the sheet; the true length dimension is only there when Break is set.
• Edge: the edges of that view, longest first (at most 40, each at least 2 in 100 of the view's longer side). It starts on the longest. The leader's arrow is at the middle of the edge.
• When a view changes (a break, for example), an edge that is no longer there shows Pick an edge, and the drawing says so until you pick one.

Where They Go

• Each symbol and frame is placed outside its view, on the line from the middle of the view through the point, turning 5 degrees at a time and then further out, until it is clear of every view, the title block, the parts table, the notes, the balloons and the other symbols, inside the border.
• A surface finish symbol's leader leaves its point along a short level line, or from the top of a leg, whichever does not cross the symbol. A frame's leader leaves from its nearer end.
• Layers: FINISH (the surface finish symbols) and GDT (the tolerance frames), added to the file only when the sheet has them. Circles are CIRCLE entities in the DXF, and the letters and numbers are plain text.

Limits

• At most 20 surface finish symbols and tolerance frames together on a sheet.
• They are placed for you. You cannot drag them yet; to move one, point it at another edge or into another view, change the scale or pick a bigger sheet. A leader can cross a line of a view or another leader.
• One leader each, to the middle of one edge. A frame cannot sit under a dimension or point at a face, a hole or a point you click; there are no composite frames, projected zones, all around signs or datum feature triangles yet.
• The symbols and frames are saved in the DXF. They are not kept after the window closes.
• Typed numbers hold at most 24 letters. Checking and placing the symbols takes at most 2 seconds; past that the window says so.

Problems

• I cannot see Add surface finish or Add tolerance frame. The section is behind Advanced (GD&T, surface finish). Tick that box in the Make Drawing window.
• The Advanced box is ticked and greyed out. The drawing holds a symbol or a frame, so the section stays shown. Remove them all with Remove to be able to hide it again.
• "There are 21 symbols. A sheet holds at most 20" Remove some symbols.
• "Symbol 1 (surface finish) says nothing yet." Type an Ra value, or pick Machining required, No machining allowed, a lay or an allowance.
• "an Ra of" with "is not offered." Type an Ra in the range shown, or leave Ra empty.
• "is not a number." Type a plain number such as 0.05, with a dot for the decimals.
• "has a hidden or control character in it." The box has an invisible character, often from pasted text. Clear the box and type the number again.
• "the diameter sign does not go with" Untick Diameter.
• "is a form tolerance and takes no datum." Set the datums to None.
• "needs at least one datum." Pick a letter for Datum 1.
• "Fill the datums in order" Datum 2 cannot be used while Datum 1 is None; move the letter up.
• "is used twice." Pick a different letter for one of the datums.
• "which is not on the sheet." Add that view (for example tick Add an isometric view), or pick another one in Attach to.
• "its edge is no longer in the" A view changed. Pick the edge again in Edge.
• "points at the true length dimension, which is only on a sheet with a broken view." Set Break, or pick a view edge.
• "finds no free place on the sheet clear of the views." Pick a smaller scale or a bigger sheet, or point the symbol at an edge in another view.
• "Placing the surface finish symbols and tolerance frames took longer than 2 seconds" Remove some symbols, or pick a bigger sheet.

Tips

• Point a surface finish symbol at the edge that shows the surface edge on, so the leader lands on the surface it is about.
• For a hole's position, attach the frame to an edge of the hole in the view that shows its outline, and tick Diameter.
• Use one general surface finish symbol pointing at the biggest face's edge, and a note for the rest of the part.

Related Pages

• Make Drawing (Views, Sections and Center Marks)
• Detail, Auxiliary and Broken Views
• Drawing Notes, Balloons and Parts Table