Free Advice #003: Use a magnet, inside a plastic bag or beneath multiple layers of plastic wrap, to clean up shrapnel from drilling, cutting, or tapping metal

Earlier this month, I wanted to replace the bolt-feet on the bottoms of some filing cabinets with wheels, so I flipped one of them on its side, unscrewed one of the foot-bolts, and tried it in the closest-looking (size-wise) pieces of my bolt size-and-thread-check set, and found that it went smoothly into the female end of the M10-1.5 checker piece. Thence to the PC and onto Taobao, found solid stainless steel wheels I liked that attached via built-in M10-coarse-thread bolts, placed an order, and waited.

When the wheels arrived, I expected the switcharoo to be quick and painless. I tilted one of the filing cabinets, unscrewed the first of its four feet, and began threading in the first of the wheels. To my great consternation, the M10-1.5-bolt-topper on the wheel wouldn’t go in more than a few turns before binding. A realization struck. I fished out my other bolt size-and-thread-check set, the non-metric one, and found that the bolt screwed effortlessly into the #3/8-16 piece’s female end. Tried it in the M10-1.5 piece in the metric set and, sure enough, it went in fine. The bolt-feet on my filing cabinets were #3/8-16 and so were the four holes on the bottom of each cabinet but the holes were much less ‘forgiving’ than the feet-bolts.

Purchased with the thought in mind that it would be better to have one and not need it than to need it and not have it, I possessed a new-in-case, never-opened set of metric taps and dies. It’s a cheap set, by the standards of taps and dies, from IRWIN HANSON and all of the pieces are soft carbon steel. In online discussions, there are authoritative-seeming posters on both sides: those claiming carbon steel taps and dies are perfectly serviceable and will last a lifetime if used and maintained properly and those of the view that carbon steel taps and dies may as well be made of butter and, if one lasts long enough to thread one hole or one a short length of metal rod, it’s a minor miracle.

Three filing cabinets and thus twelve holes to re-thread. A single set of carbon steel taps and dies containing a sole M10-1.5 tap. Tapping didn’t seem overly complex. If I screwed up one hole, it would suck but I figured I could ram the original foot-bolt back in one way or another. Tapping some holes and then breaking the tap or having it dull to the point of uselessness before I’d finished all one dozen holes would suck too. Plumbing the depths of my memory banks, specifically of YouTube machinist videos I’d watched, I came up with gems like “Go slow”, “Periodically reverse a bit before going forward again”, and “Use tapping fluid” and set to work. I have a bottle of never-opened tapping fluid, but it was still packed away in an unknown moving box, so I went with spray-bottle-dispensed WD-40.

Long story short: I got-r-done. All holes re-threaded and wheels screwed on. Happily ever after. But then, as always, came the clean-up phase of the project.

As you can see in the first photo above, I’d wadded up a paper towel behind and beneath every one of the holes to be tapped. Most of the WD-40 wound up and most of the metal shards were caught thereon. Most, but not all. This was a manual job and I’d turned the tap wrench slowly. Nevertheless, small bits of steel were scattered throughout the immediate vicinity. If the flooring in that space hadn’t been ceramic tile, I’d have laid down sheets of cardboard or a small tarp first, but the metal swarf would still have had to be dealt with.

The final step in tidying and safe-ifying the area up was a thorough wipe-around with a wet paper towel (and eyeballing the floor with a bright flashlight resting on the floor to make remaining shards and specks gleam more obviously) but the preceding step was picking up as much as possible of the stuff using a large magnet, wrapped in plastic or placed within an inside-out ziplock bag (so that the bag can be carefully turned right-side-out and zipped shut and discarded without any of the metal bits escaping). You can see the magnet I used in the second image above, with some steel crumbs sticking to the piece of clear packaging tape I placed, sticky-side-out, over the plastic.