Corkscrew milling saves USD35,000 in machine time

摘要

Corkscrew milling - different than orbital milling - provides sweat-fit hole dimensions and finish for precision dieset guide-pin holes, plus saves USD35,000 annually in machine time. Sinking large-diameter blind holes into tough hot-work steels isn't easy, but die- and-moldmakers often have no choice. They need to create guide-pin holes in mating halves of a toolset for forging, stamping or molding. Unless the holes are perfectly round and smooth-sided, the sweat-fit with the guide-pin won't hold. And if the mating holes don't align exactly, the dieset can seize or be damaged when put to use, endangering the machine and anyone nearby. The problem is perhaps most extreme in big forging dies, where guide-pin holes run big enough to hide a bagel - 2" - 4" diameter by more than 4" deep. Standard indexable mills have not worked well on guide-pin holes because they cut out-of-round or score the bore with zigzag tool marks, leading to loose sweat-fits with the guide-pins. For a lot of tool and die shops, prevailing practice is to do it the old fashioned way. Open the hole with a spade drill, then finish-bore for final size, roundness, straightness, and finish on one half of the dieset. Then repeat for the other holes until all four are done. The problem is, it's very slow. It can take a full day to complete just one toolset this way, even when all goes well.