When working on automotive engines a long heavy machinist straight edge is a must. This is the best way to tell if the mating surfaces are flat and true. That includes cylinder heads, engine blocks, intake and exhaust manifolds as well as critical sealing metal to metal covers and housings.
This 24" Bevel Straight Edge is made from hardened steel and features a satin chrome finish and is ground and lapped for straightness and parallelism. It has true right angles for all edges. One long edge is beveled with a US standard scale in increments of 1/64 of an inch. This is really handy when you need to precisely measure the length of a surface. From one end to the other accuracy is within .001 to .003 of an inch.
PLEASE NOTE: The accuracy of this tool is more than adequate for most D.I.Y. automotive engine work. For instance, if you are checking a cylinder head it will give you a really good idea if the head is warped. Of course, when you take it to the machine shop they can measure and mill to within .001 of an inch. If you are a machinist then this tool may not be for you. If you need 100 percent accuracy you will need to purchase a straight edge in the $80 to $120 range.