By Chuck Lynch
No, we aren’t talking about the Hot Wheels car track, but I got your attention, didn’t I? If you look up the definition for crisscross and crosshatch, you will find nearly identical explanations.
Crosshatch: If two sets of parallel lines crosshatch, or you crosshatch them, they are close together and cross each other.
Crisscross: (of a pattern) containing a number of straight lines or paths that intersect each other.
Over the past few years, we have really pushed the need to understand the surface finish/roughness or texture of the cylinder bore that interfaces with the piston rings. We have shared the tools required to measure the surface texture and the factors that impact the texture but there is another key factor that can impact the performance of the ring seal; and as a rule, we don’t typically give a great explanation as to why it is important. Therefore, we are going to discuss cylinder bore crosshatch; how to establish and what changes impact it.
Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2026EPQ2/#p=14
I was recently involved in a conversation regarding a V8 engine block that you would expect to have a 45-degree crosshatch. Typically, a V8 engine block would have a short cylinder and therefore that is why we would expect to see a 45-degree crosshatch. Things are not always governed by “rule of thumb” as we continue to learn. The only constant is change, right?
Rule of thumb can get you in trouble if you rely too heavily on it. Oddly enough, the idiom has a strange history. Some sources state that the rule came from the ruling centuries ago that stick that you beat your wife with could be no larger than your thumb or James Kelly’s The Complete Collection of Scottish Proverbs, 1721, includes: “No Rule so good as Rule of Thumb, if it hit,” meaning a practical approximation. So, in short, approximately is not always accurate enough to keep you from taking a beating later.
Why are there different crosshatch angles specified? Just as there are requirements for surface texture, bore geometry and size, crosshatch is a factor in the effectiveness of a cylinder and ring to work in concert. Below, I will list the parameters that should be considered when considering a crosshatch angle.
Crosshatch affects the following:
- Ring rotation
- Oil retention in the surface texture
- The rate at which oil is squeegeed back to the crankcase/oil sump by the oil control rings. (This can and will cause blow-by. If there is no oil at the interface or if there is too much oil for the rings, the rings will fail to do their duty.)
What features determine the different crosshatch angles?
- Cylinder length-long cylinders need steeper angles to get oil to return to the crankcase more easily. Short cylinders need lesser angles to retain oil.
- Horizontally opposed lay in oil and require steeper angles to get oil to return to the crankcase more easily.
- V-type engines usually have shorter cylinders…usually!
- Crankcase windage devices and vacuum pumps.
- Ring face material dictates the surface texture. Slight adjustments in crosshatch could help with oil retention at the ring/bore interface. A Nitrided ring may require a little flatter/lesser angle than is required by a moly faced ring because the moly retains oil.
Hopefully, these illustrations and definitions can help with visualization for your customers.
Too flat or too shallow a crosshatch angle will create oil control problems as oil is being pushed horizontally, not vertically down the cylinder. It can also create excessive blow-by as extremely flat angles cause the rings to ‘chatter’ as they travel in the cylinder. Caveat, engines with windage devices, vacuum pumps, aero-wing crankshafts may reduce oil on the cylinder wall and result in ring scuffing.
Too vertical (too steep) of a crosshatch angle can create excessive blow-by and high ring rotation speeds thus causing rings to align on the piston. This is also the spec for most horizontally opposed engines. Remember, application can dictate the difference between normal and absolute.
How do you establish a crosshatch angle? That is really a two-part question, I suppose.
What does the OE state that crosshatch angle should be for the application?
What control do I have with my machine to adjust crosshatch angle?
If you have a machine that has belts and pulley setting to establish a stroking rate and spindle speed, then you are not going to have as much latitude to adjust the crosshatch angle. If you have a CNC hone, you can set the angle to more exact specifications.
How can I measure the crosshatch angle in the bore? There are methods that range from fax-film to transparencies from ring suppliers to electronic methods. I recommend checking the angle of modern core engine blocks rather than go with assumptions. Several shops have added software to see a digital image of surface finish gathering equipment. You can do the same with a camera that you can put in the cylinder bore and capture the OE finish and validate what your machine is producing as well.
Everything that we touch in the engine machinist world seems closely related to an onion…you just keep peeling back layers. It is often said “don’t sweat the small stuff” but in our world, the small stuff may really be the big stuff.
Please remember that you have resources at AERA that can help you get the devil out of the details. We have an eager team that wants to help you be successful. If we don’t have the answer immediately, let us dig in for all of us in our community.
Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2026EPQ2/#p=14