38-03 Countersinking & Trimming Rear Window


After reaming the holes in the Rear Window up to #27, it was time to countersink the holes.

The holes over the Roll Bar need to have a countersink to fit a #6 screw, and the ones under the rear skin to accept the dimples.

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After practising on some scrap plexiglass from the landing light lenses, I achieved good consistent results using the countersink cage and a #27 countersink bit.

You have to be sure to place the countersink bit pilot in the holes very carefully, avoiding any sideways force … for the obvious reason!

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I used a test dimple to check for depth. But as I usual I started with flush plus 0.007″ for the skin countersinks.

In the end I went to about 0.010″.

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I used the magic potion (Isopropanol & baking soda) to lubricate & cool during the countersinking.

I found it best to go slowly, and when removing the bit from the finished hole, to keep the bit gently rotating.

It took a while going carefully, but all worked out fine.


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I marked the forward edge of the window with tape.

There wasn’t that much material to remove, about 1/8″ at the most I guess.

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There is a company called Perma-Grit here in the UK, and they make a brilliant little cutting disk which can be used in a Dremel or similar.

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Anyway, this proved great at gently removing material.

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Then I fine tuned using a sanding block with 80 grit sandpaper.

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I had heard that a sharp Cabinet Scraper is also a good tool to finish the edges.

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And so it turned out!

Great for removing fine slivers, and it came into its own for beveling the edges.

Top Tip – do not be fooled by the detail view showing the bevels on page 38-03. I don’t think they are to scale, and the bevel at the size depicted (1/64″) is a lot smaller in reality!!

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I discovered there was another trimming job not mentioned in the manual.

This picture shows one of the F-01474A Stiffener Angles, and you can see that the window needs to be trimmed to clear these.

The picture below shows how I trimmed my window to clear the Stiffener Angles.

I finished off the edges with wet & dry paper, working down to 600 grit for a mirror & smooth finish.

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