Engineer’s Straight Edge Maintenance and Care

29th February 2020


Engineer’s straight edge maintenance and care


	Shop for Engineer’s Straight Edges


		How to check that a straight edge is straight
		Without the aid of another straight edge or a surface plate, the best way to check that a straight edge is straight is to place it on a wooden board.

		With the working face of the straight edge at 90 degrees to the surface of the wooden board, run a marking knife along the length of the straight edge. Then turn the straight edge around 180 degrees and place it up against the line you have just marked.

		If there are any gaps between the line and the straight edge, then the straight edge is not straight. Note: This method is only suitable for roughly checking the accuracy of workshop grade straight edges. To accurately test if a straight edge is straight, it will need to be checked with precision tools, and this is best done at an accredited laboratory.

		Calibrating an engineer’s straight edge
		Engineer’s straight edges should be calibrated by an accredited UKAS (United Kingdom Accreditation Service) calibration laboratory in the UK or appropriate regional body in other parts of the world. The calibration laboratory should also be compliant with ISO/IEC 17025.

		UKAS publication ref:Lab 21 states that engineer’s straight edges should be calibrated at a minimum interval of yearly, in house, by competent staff, using appropriate calibrated equipment to a documented procedure. This is in addition to a minimum five yearly calibration at a UKAS accredited laboratory for which a UKAS calibration certificate is issued. A list of UKAS accredited laboratories can be found on the UKAS website.

		Cleaning an engineer’s straight edge
		How you clean your engineer’s straight edge will depend a lot on the material it is made of.

		If your straight edge has marking ink or any other fluid on it, then the first thing to do is wipe this off with a soft cloth.

		Steel and cast iron straight edges should then be sprayed with a water-repelling oil or grease and any excess wiped away with a cloth. This helps to prevent any moisture getting to the straight edge and minimises the risk of it rusting over time.

		Granite engineer’s straight edges should be sprayed with a purpose-made granite cleaner and any excess wiped off. This not only cleans the granite but helps to seal any pores in the granite structure, preventing moisture from entering which could cause the granite to crack.

		As aluminium straight edges do not rust they only require brushing and wiping clean of any debris or fluid before being stored.

		Storing an engineer’s straight edge
		Engineer’s straight edges should be stored separately from other tools to prevent damage to their working face.

		You should be aware that steel and cast iron straight edges can rust if they are left in a moist atmosphere, so it is particularly important to store these in a dry place.

		Some engineer’s straight edges will come with their own storage cases to prevent damage to the working face. If yours doesn’t, it is possible to buy these separately, or you could make one yourself. Many feature a form fitting rubber foam interior that provides excellent insulation from any knocks and shocks that could damage or affect the accuracy of your engineer’s straight edge.

		If you are not using a storage case, then engineer’s straight edges should be stored either supported by the supporting points/feet, or with the working face lying on a similarly flat surface such as a reference plate. This will minimise any deflection that may be caused to the working face of the straight edge.

		Some smaller and thinner rectangular and knife edge engineer’s straight edges have a hanging hole on one end. This allows the straight edge to be hung up when not in use and minimises forces through the working face, so reducing any possible distortion of the working face.

		Can a damaged engineer’s straight edge be repaired?
		If an engineer’s straight edge has become damaged, it may be possible to repair it, depending on the nature of the damage sustained. Minor damage such as slight warping of the working surface may be repaired by having the straight edge re-scraped or lapped.

		This should be carried out by an accredited laboratory in order to maintain and certify the accuracy of the straight edge. More serious damage, such as dents to the working surface, bent straight edges or cracks in granite straight edges will most likely require the straight edge to be replaced with a new one.

		How long does an engineer’s straight edge last?
		If properly cared for and maintained with regular calibration, then an engineer’s straight edge should last many years.