Cylinder Wall Finish

[AlisoBob]

"Many shops bore or rough hone cylinders to within .003 inch of final oversize (.010 to .030 in. depending on the application), then finish hone the last .003 in. of the bore with #220 or #280 grit vitrified abrasives. "Most shops do not have a profilometer to measure surface finish parameters such as RA, RK (core roughness), RPK (average peak height) and RVK (average valley depth), bearing area and so on, so they rely on stone grits along with the right honing pressure, head speed, stroke rate and lubricant to achieve the desired bore finish. Consequently, there�s no way to know if the bore finish actually meets the requirements of the ring manufacturer or the OEM, unless someone complains about excessive ring wear, blowby or oil consumption. But even if you have not experienced any ring problems, it does not mean the cylinders are as good as they could be or should be."

Roosty, do you measure RA, RK, RPK, or RVK?

Just curious.....

[bigred1977]

[Roostius_Maximus]

RA, but we dont check it all the time. Only when breaking in a new set of diamond stones do we check to see if they are correct. Our guys know on the chart we've made what pressure and how many strokes per minute equal what ra, and similar, but not as accurate on the mandrel machines you visually check the degree of crosshatch and watch your pressure.