Mechanisms: Abrasives

In our “Mechanisms” series, we’ve featured the fascinating bits and pieces that go into making our mechanical world work. From simple machines such as screws and levers, from springs to couplings, and even more complex mechanisms like zippers and solenoids, we’ve covered the gamut. But we haven’t talked about one of the very earliest mechanisms, captured from nature by our clever ancestors to do useful work like grinding grain and shaping materials into tools: grit, sand, abrasives.

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Fail of the Week: The Semiconductor Lapping Machine That Can’t Lap Straight

It seemed like a good idea to build a semiconductor lapping machine from an old hard drive. But there’s just something a little off about [electronupdate]’s build, and we think the Hackaday community might be able to pitch in to help.

For those not into the anatomy and physiology of semiconductors, getting a look at the inside of the chip can reveal valuable information needed to reverse engineer a device, or it can just scratch the itch of curiosity. Lapping (the gentle grinding away of material) is one way to see the layers that make up the silicon die that lies beneath the epoxy. Hard drives designed to spin at 7200 rpm or more hardly seem a suitable spinning surface for a gentle lapping, but [electronupdate] just wanted the platter for its ultra-smooth, ultra-flat surface.

He removed the heads and replaced the original motor with a gear motor and controller to spin the platter at less than 5 rpm. A small holder for the decapped die was fashioned, and pinched between the platter hub and an idler. It gently rotates the die against the abrasive-covered platter as it slowly revolves. But the die wasn’t abrading evenly. He tried a number of different fixtures for the die, but never got to the degree of precision needed to see through the die layer by layer. We wonder if the weight of the die fixture is deflecting the platter a bit?

Failure is a great way to learn, if you can actually figure out where you went wrong. We look to the Hackaday community for some insight. Check out the video below and sound off in the comments if you’ve got any ideas.

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Bolt-Together Belt Grinder for the No-Weld Shop

Belt grinding offers a lot of advantages for the metalworker, and since belt grinders are pretty simple machines, shop-built tools are not an uncommon project. A bolt-together belt grinder makes this tool even more accessible to the home gamer.

With no access to a welder but with a basic milling machine and an ample scrap bin at his disposal,  [IJustLikeMakingThings] had to get creative and modify some of the welding-required belt grinder designs he found online to be bolt-up builds.  The key to a cool running belt grinder is for the belt to be as long as possible, and the 2″x72″ belt seems to be the sweet spot, at least here in the States. Machined drive and idler wheels with the crown needed for proper belt tracking were sourced online, as was the D-bracket for holding the two guide wheels. But the rest of the parts were fabricated with simple tools and bolted together. [IJustLikeMakingThings] provides a lot of detail in his write-up, and it shouldn’t be too hard to build a belt grinder just like this one.

Looking for other belt grinder plans to compare notes? Here’s a grinder with an even simpler design, but with welding required.