Achievement Unlocked: Drill a Square Hole With a Rotary Broach

square hole rotary broachThere are times in a man’s life when he needs to drill a square hole through an 8mm thick piece of steel. If that man doesn’t have one or two thousand dollars to spend on commercial tooling to do this, he might just shrug his shoulders and make do with round holes. But if that man is [Chris], he rolls up his sleeves and makes his own tool to drill square holes with a rotary broach.

This tool that [Chris] has named the Wobble Drive drills a square hole by applying force to each of the corners of a square bit one a time. How, you might ask, did he achieve this? With a two-part tool and the power of offset driving. He took a cylindrical chunk of steel and bored a little cup for a ball bearing to move around in. He didn’t have one rolling around his tool box, so he liberated one from a 2209 double row self-aligning cylindrical bore with a screwdriver. Then he hammered a square rod of steel into a hole in the other end and made the rod’s bottom a little bit concave on the grinding wheel. He also took a little off the sides to aid the weeble wobble action. A second steel cylinder with a ball bearing cup sits in the chuck of his Bridgeport mill and wobbles the tool bit through the power of a 1/4″ offset.

[Chris] tested it on the same sacrificial plate he used to demonstrate the awesome power of Lil’ Screwy, his 100-ton homebrew press. He drilled a 3/8″ round pilot hole and then went to work with the Wobble Drive. The tool bit side proved to be too long to provide the requisite stroke, so he cut it down by about half. Once the tool has chewed through the steel, the tool bit decouples at the ball bearing and [Chris] has himself a square hole and that much more hacking cred.

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Behold Lil’ Screwy, A Homebrew 100-Ton Press

Here we have a magnificent example of the power of the inclined plane. [Chris] has built Lil’ Screwy, a 100-ton home-built press for about $35 plus scrap on hand. He demonstrates its frightening power by punching a 17-mm hole through 8mm-thick steel using an Allen key.

As [Chris] explains in his hilarious video waiting for you after the jump, the force comes from using really big screws. Lil’ Screwy uses four 1-inch L7-rated ready rods with eight threads to the inch. The bolts run between two 1″ steel plates to form the press. In the top plate, he drilled 1″ holes. The bottom holes are drilled out 7/8″ and tapped so the two plates clamp together with awesome crushing power when you twist the giant coupling nuts.

[Chris] milled a pocket in the underside of the top plate for a big neodymium magnet that will keep, for instance, a 17-mm Allen key in place while you punch a piece of steel with it. He has a ring of smaller ones embedded into the bottom plate to hold supports in place for broaching.

As a special bonus, [Chris] shows you how to stick it to the man when it comes to using that last bit of Never-Seez in the can, and also how to make your decals temporarily repositionable.

[Read more...]

Rebuilding a Bridgeport mill

It looks like the Internet’s resident steampunker is moving up a century or two. [Jake Von Slatt] rebuilt the CNC portion of a Bridgeport Series II mill so it can interface with a computer. It’s a feat even more impressive than moving the mill into [Jake]‘s garage.

The first step of the build was tearing out the BOSS 5 industrial microcomputer and replacing it with a Win XP laptop running ArtSoft’s Mach 3. This allows G-code to be displayed directly on the screen. The old power supply for the mill did give [Jake] a few problems. The Gecko stepper drivers that replace the old electronics couldn’t handle the voltage of the old power supply. That can be dealt with by opening the transformer and removing a few turns of wire.

[Jake] has been sending in a few of his hacks as of late, so it’s good to see Hack a Day has another fan, especially one of [Mr. Von Slatt]‘s caliber. There is a problem with the mill modifications though – [Jake] hasn’t figured out how to program it. If any HaD readers would like to chime in on the best way to program G-code for the mill, feel free to leave a message in the comments.

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