Bore-Repair

I drilled a bore that came out 2mm off position. The part was a hydraulic cylinder barrel forged from 4140 steel, about 700mm long with an outside diameter of 180mm. The bore was supposed to be 80mm diameter through the full length, positioned within 0.2mm of the centerline. When I put the part on the CMM after the first drilling pass, the CMM reported the bore centerline was 2.1mm offset from the print position at the mid-length point and 2.4mm offset at the far end. ...

Sleeving is a repair technique I have used to salvage deep hole drilling parts when the bore was machined oversize, damaged during drilling, or worn in service. The process involves boring the damaged hole to a larger diameter and installing a thin-walled sleeve that restores the original bore size. I have saved parts worth thousands of dollars this way. Problem Description An oversized bore in a deep hole drilling application can mean the part is scrap. The bore diameter is outside tolerance, the surface finish is damaged, or the bore is out of round. Replacing the part entirely costs 3-5 times what a sleeving repair costs and takes longer to procure. ...