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Please note, our Harmondsworth office will be closed on Friday 6th December and will re-open on Monday 9th December. For assistance during this period, please call the Widnes office on Tel: 0151 495 3111. Apologies for any inconvenience.

Grading Definitions

31.     Check is a lengthwise separation of the wood, which generally occurs across the rings of annual growth.

         31 – a.         Small checks are not over 1/32” (1mm) wide and not over 4” (102mm) long.

         31 – b.         Medium checks are not over 1/32” (1mm) wide and not over 10” (254mm) long.

31 – c.         A through check is one extending from one surface through the piece to the opposite surface or to an adjoining surface.

32.     Edge Irregularities are those that occur in the process of machining, i.e. chipped out grain, or torn out knots.

33.     Free of Heart Centre (FOHC) means when the pith is not enclosed within the four sides of the piece.  An occasional piece showing pith for a short distance may be accepted.

34.     Grain. The fibres in wood and their direction, size, arrangement, appearance or quality.

34-a. Vertical Grain (VG) timber is a piece or pieces sawn at approximately right angles to the annual growth rings so that the rings form an angle of 45°or more with the surface of the piece.  If vertical grain is required it must be specifically stated on the order.  Pieces of clear timber 10 inches wide (254mm) and wider showing vertical grain for at least two thirds of the face width shall be considered vertical grain.

34-b. Flat Grain (FG) (sometimes referred to as Slash Grain) timber is a piece or pieces sawn approximately parallel to the annual growth rings so that all or some of the rings form an angle of less than 45°with the surface of the piece.

34-c. Random Grain (RG) or Mixed Grain (MG) refers to any combination of vertical and flat grain.

35.     Slope of Grain is the deviation of the line of fibers from a straight line parallel to the sides of the piece.  The deviation is expressed as a ratio, e.g. the slope of grain is 1 in 8, 1 in 10, 1 in 12, etc 

36.     Torn Grain occurs when parts of the grain have been chipped or torn out around the knots or local disturbances of grain, and it shall be admitted if considered no more damaging in effect than other irregularities mentioned in the respective grades.

37.     Knots.  Knots shall be considered as to form, size and quality.


         37-a.  As to their form, knots shall be considered as round and spike.

         37-b.  A spike knot is one sawn in a lengthwise direction 


37-c.  As to their size, knots admitted shall be considered in accordance with the size of the piece.

37-d.  The average of the maximum and minimum diameters shall be used in measuring knots except spike knots.  Spike knots shall be measured by the displacement method.



37-e.  As to their quality, knots shall be considered as sound and tight, loose, unsound, or in clusters.

37-f.   A sound and tight knot is red or black, solid across the face and so held by growth or position that it will retain its place in the piece.

37-g.  A loose knot is one not held firmly by growth or position in the piece.

37-h.  An unsound knot contains decay.

37-i.   A cluster of knots is a group of knots with a deflection of grain around the entire group. 

38.     Pitch Streaks are well-defined solid accumulations of pitch.

39.     Pockets (pitch or bark) are well-defined openings between the rings of annual growth that develop during the growth of the tree.  They usually contain pitch or bark.  Pockets shall be classified as small, medium and large as follows:

39-a.  Small pocket - 1/8” (3mm) in width and 4” (102mm) in length, or ¼” (6mm) in width and 2” (51mm) in length.

39-b.  Medium pocket – 1/8” (3mm) in width and 8” (203mm) in length, or 3/8” (10mm) in width and 4” (102mm) in length.

39-c.  Large pocket – any pitch pocket more than  1/8” (3mm) in width and over 8” (203mm) in length, or more than 3/8” (10mm) in width and 4” (102mm) in length. 

40.     Rate of Growth.     When an annual ring or rate-of-growth specification is mentioned, it shall mean an average number of annual rings at either one end or the other of the piece over a 3” (76mm) line measured at a right angle to the rings and located as follows:

40-a.  In boxed-heart pieces, the 3” (76mm) line shall be representative, and where the least dimension is 6” (152mm) or less the line shall begin at a distance of 1” (25mm) from the pith.

40-b.  When the least dimension is more than 6” (152mm), the 3” (76mm) line shall begin at a distance from the pith equal to ¼ the least dimension of the piece.

40-c.  In side-cut pieces (pith not present) the number of annual rings per inch shall be measured along the centre three inches of the longest radial line which can be drawn at either one end or the other of the piece.

41.     Close Grain shall mean an average on either one end or the other of the piece of not less than six (6) annual rings per inch (25mm), measured as described in Para. 40.  Pieces averaging five (5) annual rings per inch (25mm) shall be accepted as the equivalent of close grain if having one third (1/3) or more summerwood.  Summerwood is the dark portion of the annual ring.  The contrast in colour between the summerwood and springwood shall be distinct.

42.     Medium Grain shall mean an average on either one end or the other of the piece of not less than four (4) annual rings per inch (25mm), measured as described in Para. 40.

43.     Sap (Sapwood) is the outer layers of growth between the bark and the heartwood which contain sap.

         43-a.  Bright sap shows no stain.

44.     Sap Stain is a discolouration of the sapwood.  It has no effect on the intended use of the pieces in which it is permitted but affects appearance in varying degrees.

44-a.  Light stain is so slightly discoloured that it does not affect natural finishes.

44-b.  Medium stain has a pronounced difference in colouring.  Note: Sometimes the usefulness for natural finishes but not for paint finishes is affected.

44-c.  Heavy stain has so pronounced a difference in colour as to obscure the grain of the wood but the timber containing it is suitable for paint finishes.

45.     Shake is a separation of the grain either across or parallel to the annual rings.

46.     Split is a separation of the wood in the lengthwise direction. 

47.     Square Edged shall mean free from wane.

48.     Wane is bark or lack of wood.

         48-a.  Slight wane is ½ across the corner for 1/16 the length. 

49.     Wormholes.

         49-a.  Pin wormhole is one not over 1/16” (2mm) in diameter.

         49-b.  Small wormhole is one not more than ¼” (6mm) in diameter.

         49-c.  Large wormhole is one over ¼” (6mm) in diameter.

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