| Term |
Definition |
| Machine burn | Darkened burn mark on dressed timber caused by overheating of knives or rollers. Sometimes called ‘pause marks’. |
| Machine graded pine (MGP) | Structural grading system used for certain plantation pines that measures the bending stiffness of a piece in terms of its ‘modulus of elasticity’ (MOE). |
| Machine ridge | Lengthwise ridge on dressed timber caused by a gap in the cutter. |
| Modulus of Elasticity (MOE) | Measure of the stiffness of a piece expressed in megapascals (MPa). Used as the basis of MGP grades. For example, a piece graded to MGP 10 will have an MOE of 10,000 megapascals (MPa). |
| Modulus of Rupture (MOR) | Pressure required to rupture the fibres in a sample piece of timber in a test machine. Used in the calculation of F grades, where the formula is based on the MOR of the species divided by a safety factor, after which allowance is made for specific defects in the piece. |
| Moisture content (MC) | Weight of the moisture contained in a piece of timber – expressed as a percentage of the weight of the woody substance. |
| Mould | Superficial fungal growth on timber, often in form of a woolly or furry coating. Sometimes called ‘surface mould’. |
| Moulding | Timber that has been machined to a profile for use in finishing or decorating. |
| Needle trace | Marks on the surface of softwood timber caused by needle-type leaf casings that have become embedded in the wood tissue. |
| Nominal size | Cross-sectional size of a piece in its sawn state, without taking into account the reduction in size that may occur due to shrinkage, dressing, etc. Sometimes referred to as ‘called size’ or ‘named size’. |