Additional tips for part finishing

Wrapping up the theme of my previous three columns, presented here are more tips and tricks for effectively performing finish work.

■ A ceramic blade scraper is effective for deburring gummy, grabby plastics like ultrahigh-molecular-weight polyethylene and ABS (acrylonitrile-butadiene-styrene) plastics. The ceramic has just the right amount of edge sharpness to peel off burrs without gouging softer materials. Another trick is to put soft plastics in the freezer. This makes the burrs more frangible and easier to snap off crisply and cleanly.

All images courtesy T. Lipton

Media wedging is a deadly booby trap when deburring parts in a vibratory tumbler.

Mask features you want to protect or remain sharp while the rest of the part goes the vibratory tumbler deburring cycle.

■ Vibratory tumblers are a double-edged sword, with the potential to decrease hand deburring time by a huge amount, or to destroy an otherwise simple job in a matter of minutes. The secret is in the media and part geometry. The deadly booby traps are material cross contamination and media wedging into and plugging part cavities—not to mention just plain losing small parts. It’s a real pain to remove ceramic media from a tapped blind-hole without messing something up, and you can waste significant time trying to find small parts if you’re not set up properly. Run sample parts first before you commit a large batch of critical parts. Also, beware of overloading large parts, which can clank together and cause serious part damage.

■ Always note the part count when you drop a batch in a tumbler. There’s nothing like finding a missing part months later when you change media.

■ For really small parts, you can use a subcontainer inside the main bowl. This prevents tiny, gray parts from becoming hopelessly lost in a sea of tiny, gray media. It’s also a neat trick to allow you to switch media sizes and shapes without having to dump 300 lbs. of abrasive to find one little part.