Aircraft Sheet Metal – Drilling Fastener Hole at 90 degrees to surface!

A Drill Square is likely a Good Choice

The use of a Drill Square is a simple yet common sense approach to improving the quality and accuracy of fastener holes

Have you ever experienced a time when you wished you had a more precisely drilled a fastener hole?

It may not be that critical if you are just drilling rivet holes to fasten two pieces of thinner sheet metal (eg.  0.020″ up to 0.032″ thick sheets).  If the stack-up is thin, the angle of the fastener (rivet) hole is not precisely at 90°  to the surface of the sheet you say “What’s the dig deal?”  The result only slightly adversely affects the installation of the rivet or the strength of the joint.  As a result, forming this inferior joint, the slight misalignment might seem acceptable, but certainly not the outcome you wanted.

“Holemaking” at Precisely 90° and Precisely the Correct Location.

Two examples of fastener hole that require a more precise fastener fit are:

  • a fastener hole to accept  a “Hilock” or other high strength fastener;  or
  •  a fastener hole drilled through thicker or multiple layers of metal

As a result, these fastener holes must be drill at precisely 90° to the surface of the sheets.  It is especially relevant to note the holemaking process must be precise. It is to be accomplished without compromise.

Even experienced craftsmen, from time to time probably need a bit of help. Therefore, even experienced  personnel can benefit while hand drilling from drilling aids.  Technician work constantly to ensure fastener holes are at 90° to the surface of the sheet.  Drill blocks, Drill Egg Cups and other devices are extensively employed as drilling aids by many.

If adequate access is a problem, or a quick and simple solution is needed, a Drill Square is a good ; some might even say a smart choice.

Drill Square
Drill Square with drill bit ready to drill a precise 90 degree hole

At first glance the Drill Square seems to simple, even somewhat “silly”.  However, once you have experience the subtle improvement in the precision of your work, its not silly anymore.

In conclusion, whether you are new to the trade, or are an experienced sheet metal/structures technician, the tools offered on this website can help you to be a better and more precise craftsman.

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