case mod 101: cutting a freestyle, low-profile window

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Completing the cutout for this steel panel took around 90 minutes. I hear people complaining that cutoff wheels shatter easily–if you have the correct technique, they don’t. One wheel was enough to cut the entire window opening, and there was enough material left on the wheel that I kept it. Remember that you are using a fast-moving abrasive edge to grind away the material. Listen to the tool and you can hear when it gets less effective.

cutting complete
we’ve finished cutting
insert removed
so we remove the scrap from the cutout
my used cutoff wheel
my used cutoff wheel and a new wheel for comparison–if you break wheels you are applying too much pressure

The cut edge needs to be deburred. A file works well for removing the loose metal that the cutting leaves behind. Files can remove a lot of material, so if you need to straighten an edge, a flat file can help. If you just need to deburr, a light tough with the file gets the job done. Removing material takes considerably more pressure.

file the edge
a file removes the burrs from the cut edge

After deburring, our corners look much cleaner, but you see the wheel has a tendency to make a cut that looks more polygonal than rounded. A drum sander bit can remove material and even out the curvature of our rounded corners. Again, a light touch is called for because we want to avoid removing much material. Just shaping the curve is best accomplished with a medium speed and fairly long strokes that draw the bit over the rough edge. Sanding drums can really mess up your finish if you slip, so go carefully.

a radius corner
this corner could be smoother
after sanding
the sanding drum helped shape the radius corner

The final step in finishing the cut edge is sanding. After sanding, the edge will be perfectly safe to touch, and feel as smooth (or smoother usually) as a factory finished edge. Using fine grit on a sanding block is just the thing for the straight edges. Once those are cleaned up, take the paper off and use your hands to finish the curved corners. You’ll feel any irregularities in the curves, and you can go back and address these with the sanding drum if they warrant it.

the sanding basics
basic sanding equipment: wet/dry sandpaper and a sanding block
work the flat edges
the flat edges of your cutout can be straightened and smoothed with a sanding block

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