Weld-Repair

Deep hole drilling is a high-risk process. When something goes wrong – a drill breaks in the bore, the bore wanders off position, or the surface finish is out of spec – the part is not necessarily scrap. I have salvaged thousands of dollars worth of components by knowing how to repair and rework bores. The key is knowing when a part can be saved and when it cannot. I have a simple rule: if the repair costs less than 60% of the replacement cost, it is worth doing. Anything over that and the customer is better off starting fresh. ...

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. ...