Drilling Techniques

When starting to repair a stone break, one of the first things a professional repair technician does is determine whether or not this break will require drilling. Most professional technicians can tell at a glance whether it will be needed. If there is a bullseye (dark circles under the impact point), it will normally NOT require drilling. If, however you question whether you need to drill or not there are a few steps you can take to determine this.

The most common step to determine drilling is to take one drop of thin, stone damage resin and place it on the impact point. If you see resin seep into the break, the impact point will not require drilling. If no resin flows in, drilling is required.

Drill into the impact point if there is no bullseye. About 3-5 seconds is enough. Then using a size 14 sewing machine needle place tip in hole and tap lightly with a razor blade holder (the one shaped like a piece of gum). This will make a miniature bullseye which will allow easy access to the crack or cracks, (this technique has been used for more than a decade.) The rule of thumb in windshield repair is if it didn’t fill, drill. That means any part of the break not filled with resin should be drilled and filled or your repair is worthless. When not drilling into an impact point, drill about half way through the outer layer and then tap. Do Not Drill into the Lamination, that would leave a permanent blemish. While her humor

Break Description Diagram Drilling Technique

  • Star: Establish a shallow pilot hole in the pit. Remove the bit from the pilot hole before starting to drill a shallow angle hole. Drill to extreme angle. Drill toward the hard-to-fill crack(s).
  • Disconnected star break: Lightly press inside the glass to see if the crack connects with the pit. Establish pilot hole in the pit. Drill at an angle toward the disconnected crack. Expand pit toward the crack and drill at an angle again. Drill into the visible beginnings of the disconnected crack(s).
  • Half Bullseye: Drill into the air space only. Inject the break through the drill hole. Cure the break and pit.
  • Bubble in cured pit: Drill an oblong (not round) opening in the drill hole. Refill and cure the pit.
  • Combination with Fishhooks: Drill the elbows and ends of the fishhooks. Cover the center of the breakfishhooks with tape. Cure the resin-filled fishhooks. Remove the tape. Repair the remainder of the break.
  • Combination with Bees Wings: Attempt to fill the break without drilling. If necessary, establish a pilot holebees’ wings and drill an angular hole toward each large crack. Drill into each bee wing in the widest area of the crack. Inject through each drill hole.
  • Combination with Impacted Bullseye: Establish deep pilot hole in the pit. Widen the deep drill hole to develop flow
    impacted bullseye to the cracks deep in the cone. Drill again immediately next to the existing pit if the cracks are not filling.
  • A Cured Repair Containing an Air Pocket: Large unfilled air pockets should be drilled and filled. Small air specks pose an air pocket no danger of “crack out” and should be left untouched.
  • Combination Break with a Long Radial: Drill the end of longer cracks (over 21⁄2″). Use drill coolant or resin when a long radial drilling deep in glass with a carbide drill bit. Fill crack, then bullseye.
  • Baseball Break: Drill one end of break. If necessary, drill one end of the break and vacuum from the opposite end of the break.
  • Star with No Impact Pit: Drill a deep pilot hole in the the intersection of the radial cracks. Drill shallow no impact pit angle holes only if the break will not fill. Drill Deeper. Drill a hole next to the first hole. 
  • Edge crack: Lightly press the inside of the crack (from inside the windshield) to determine the location of the crack. Drill a hole about 3⁄16″ beyond the visible end.
  • Star: Establish a shallow pilot hole in the pit. Remove the bit from the pilot hole before starting to drill a shallow angle hole. Drill to extreme angle. Drill toward the hard-to-fill crack(s).
  • Disconnected star break: Lightly press inside the glass to see if the crack connects with the pit. Establish pilot hole in the pit. Drill at an angle toward the disconnected crack. Expand pit toward the crack and drill at an angle again. Drill into the visible beginnings of the disconnected crack(s).
  • Half Bullseye: Drill into the air space only. Inject the break through the drill hole. Cure the break and pit.
  • Bubble in cured pit: Drill an oblong (not round) opening in the drill hole. Refill and cure the pit.
  • Combination with Fishhooks: Drill the elbows and ends of the fishhooks. Cover the center of the breakfishhooks with tape. Cure the resin-filled fishhooks. Remove the tape. Repair the remainder of the break.
  • Combination with Bees Wings: Attempt to fill the break without drilling. If necessary, establish a pilot holebees’ wings and drill an angular hole toward each large crack. Drill into each bee wing in the widest area of the crack. Inject through each drill hole.
  • Combination with Impacted Bullseye: Establish deep pilot hole in the pit. Widen the deep drill hole to develop flow
    impacted bullseye to the cracks deep in the cone. Drill again immediately next to the existing pit if the cracks are not filling.
  • A Cured Repair Containing an Air Pocket: Large unfilled air pockets should be drilled and filled. Small air specks pose an air pocket no danger of “crack out” and should be left untouched.
  • Combination Break with a Long Radial: Drill the end of longer cracks (over 21⁄2″). Use drill coolant or resin when a long radial drilling deep in glass with a carbide drill bit. Fill crack, then bullseye.
  • Baseball Break: Drill one end of break. If necessary, drill one end of the break and vacuum from the opposite end of the break.
  • Star with No Impact Pit: Drill a deep pilot hole in the the intersection of the radial cracks. Drill shallow no impact pit angle holes only if the break will not fill. Drill Deeper. Drill a hole next to the first hole. 
  • Edge crack: Lightly press the inside of the crack (from inside the windshield) to determine the location of the crack. Drill a hole about 3⁄16″ beyond the visible end.