Tech Tips: Drilling and Burs

When do I drill? Which bur should I use? Are carbide burs really better than diamond burs? Those are three widely debated topics that we here at Delta Kits happen to know quite a bit about. By the end of this article, I hope to have cleared up any confusion still out there regarding any of these subjects.

“When do I need to drill a break?” The debate rages on. We at Delta Kits recommend drilling breaks only if you are unable to get the resin to flow into the break, or there are cracks longer than a couple of inches present. In most cases resin will be able to fill the break, even when there is very little glass missing from the impact point. Many technicians drill the break to create a large channel so the resin will flow more easily. This does speed up the repair, but it also affects the repair cosmetically. Each time you drill a break; there will be a visible drill hole. It is up to you to decide if the cosmetic difference is worth the extra couple minutes. To me it is definitely worth the wait. But, sometimes you have to drill. Every once in a while you come across a chip that doesn’t have enough glass missing from the impact point to inject the resin. In those instances, just drill through the center of the impact point or air pocket. You may also want to drill the end of long cracks. By drilling the end of a crack, using your slide hammer to pop a mini bull’s-eye, and filling it with resin, you will stop the crack from growing.  Remember; do not drill past the first layer of glass. About 1/16 of an inch is as deep as you should ever need to drill.

“What is the best drill bur for windshield repair?” Now here is something to argue about. You can go a couple different ways on this one. Many technicians stick to one all-purpose bur, and others carry several styles and use the one best suited for the situation. Let’s take a look at your choices.

FG701 (hole size .047in) – The FG701 is “Delta’s Choice” because we feel it is the best all around bur. It is a fast cutting, extremely durable tapered bur, and can be used in just about any situation that might come up. The FG701 is the perfect size for drilling the ends of cracks because the tip of the slide hammer fits neatly in the hole, and “pops” a perfect bull’s-eye nearly every time. Make no mistake, smaller probes often crush the glass inside the drill hole or worse yet, create tiny cracks at the end of the large crack you are trying to stop. Smaller holes will not accommodate the slide hammer, and too tight of a fit can also cause damage to the glass.

FG2 (hole size .039in) – The FG2 is popular with many technicians because it the round head makes it less apt to skip or travel across the glass when you are starting to drill.  The FG2 also drills a smaller hole, which is preferable to many technicians. Although not as durable as the FG701, the FG2 still out performs most other burs on the market for most break types, but is not recommended for stopping long cracks.

FG170L (hole size .039in) – The FG170L is great for the technician that desires the benefits of a tapered bur, but with a long narrow point that drills the same size hole as the FG2.

FG169L (hole size .031in) – The FG169L also features a long tapered point, but drills an even smaller hole.  The FG169L is a great bur for very small breaks where a larger drill hole may be very apparent.

FG329 (hole size .024in) – The FG329 features a unique pear shaped head that drills the smallest hole of any Delta Kits bur. Many technicians feel the FG329 drills faster and lasts longer than the FG2, yet provides the skip free qualities that make the FG2 so popular. However testing by Delta Kits produced data suggesting the FG329 is less durable than the FG2.

Conclusion:  As a rule, the smaller the hole size, the less durable, and easier it is to break the bur. Delta Kits does not sell diamond burs as carbide burs are far superior in strength and speed. Carbide burs are also much less expensive, although that is not our main consideration. Size does matter…at least when you intend to “pop” a bull’s-eye at the end of a crack. My opinion is that if you only want to carry one bur in your tool box the FG701 should be that bur. That said it’s much like buying a car. Some people swear by a Chevy, and others buy only Fords. The only way you can know for sure which one will best suit your personal needs is to try them for yourself.