Choosing the right drill bit size for rivets seems easy but it often trips people up quickly. Holes must be drilled before installing the rivets, just like for bolts or pins. Logically you use a drill of the same size, for instance a 1/8″ drill bit for 1/8″ rivets, because a 1/8″ bit makes a hole that fits a 1/8″ rivet.
Rivets fit a particular size, so a 3/16″ rivet goes in a 3/16″ hole The end part is a bit bigger, and the back part expands to tie two bits together.
How to Choose the Right Drill Bit for Rivets
For solid rivets there is a handy trick called the Rule of 7. A #40 drill bit goes with a -3 rivet, because 4+3=7, and a #30 drill bit for a -4 rivet, because 3+4=7. Like this AN426-AD3 and AN470-AD3 rivets both require a #40 drill.
Similarly AN470-AD4 and AN426-AD4 rivets use a #30 drill. The common part in the names is AD3 or AD4. Solid rivets are named by type, diameter and length.
Use a #30 dril bit.
In typical flush riveted metal projects you use mainly 3/32″ or 1/8″ rivets. For 1/8″ rivets (about 3.2 mm) a #30 drill works well. It has a diameter of about 0.1285 inches or 3.26 mm.
A #30 drill is a bit bigger than a 1/8″ drill by some thousandths, which eases the install of the rivet and cleco. A #30 is for A4 (1/8″) rivets and copper clecos.
For removing rivets there are also specific drill sizes. A letter D drill (0.246 inches) is used for 1/4″ MS20470 and AN470 solid rivets. A 0.191″ bit works for 3/16″ rivets, and 0.159″ for 5/32″ rivets.
One way for removal is first drill a 1/16″ hole for a guide, then a 3/16″ drill to remove the rivet head.
Rivet nuts work differently. Different grades of rivet nuts require different hole sizes. For instance an M8 rivet nut requires an 11.0 mm drill.
1/4″ rivet nuts go well with a 23/64″ drill. 4-40 threaded rivet nuts are very small, so the body and hole will be small too. It is always good to check a chart for rivet nut drill sizes for right specs.
5 mm and 3.5 mm drill bits simplify the work with common metric rivets. Right drill sizes help to avoid pain when putting in rivets, so a bit of clearance is usefull. Keep the drill straight to the surface, considering the material and grip range.
A sharp drill of the right size makes everything much more easy. Use the righttool.
