Sharpies and Glue Sticks Fight the Gummy Metal Machining Blues

“Gummy” might not be an adjective that springs to mind when describing metals, but anyone who has had the flutes of a drill bit or end mill jammed with aluminum will tell you that certain metals do indeed behave in unhelpful ways. But a new research paper seeks to shed light on the gummy metal phenomenon, and may just have machinists stocking up on office supplies.

It’s a bit counterintuitive that harder metals like steel are often easier to cut than softer metals; especially aluminum but also copper, nickel alloys, and some stainless steel alloys. But it happens, and [Srinivasan Chandrasekar] and his colleagues at Purdue University wanted to find out why, and what can be done about it. So the first job was to get up close and personal with the interface between a cutting tool and metal stock, to observe the dynamics of cutting. In a fascinating bit of video, they saw that softer metals tend to fold in sinuous patterns rather than breaking on defined shear planes.

Source: American Physical Society.

Having previously noted that cutting through Dykem, a common machinist’s marking fluid, changes chip formation in soft metals, the researchers tested everything from Sharpies to adhesive tape and even correction fluid, and found that they all helped to reduce the gumming action to some degree. Under their microscope they can clearly see that chips form differently once the cutting edge hits the treated surface, tending to act more brittle and ejecting rather than folding. They also noted a marked decrease in cutting force for the treated metal, and much-improved surface finish to boot.

Will Sharpies and glue sticks enter the book of old machinist’s tricks like gauge-block wringing? Only time will tell. But for now, this is a pretty fascinating bit of research that you might be able to put to the test in your shop. Let us know what you find in the comments.

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Hand-Machined Companion Cube Can Be Destroyed and Rebuilt

[Michael Gainer] is a big fan of Portal, and it shows in the Weighted Companion Cube he made. [Michael] hand-machined the many pieces that comprise the Cube’s body and medallions out of 6061 aluminum. Dykem was used to transfer the marks for accurate machining, and the color is powder-coated to a heat tolerance of 400F. A CNC was used to make the distinctive hearts. [Michael] notes the irony was “very Portal” in having them cut by a heartless machine when everything else was done manually. The attention to detail is striking, the level of design more so when [Michael] proceeds to incinerate the poor Companion Cube with a brush burner. In the video shown at the link above, the Cube falls apart as the glue holding it together melts. When all is said and done, just grab more glue to bring that Cube back to its six-sided glory. Repeat to your heart’s content. Huge success! We have to be honest, after seeing all those pieces, we aren’t sure we’d want to do this very often. Companion Cubes have been featured in various iterations on Hackaday before, but they were never built with the idea of repeatedly destroying and rebuilding them. This novel take would make GlaDOS proud.

[Michael] has plans to put an Android device inside it with some light and temperature sensors. He wants to give it a voice resembling Portal’s turrets so it can whine when it needs to be charged or scream when it’s too hot or cold. He dubs this next project the “Overly Attached Weighted Companion Cube.” It wouldn’t be a good idea to incinerate this upcoming version, though we’d probably be inclined to if it demanded so much of our attention!