Which Bur for Windshield Repair?

When do I drill? Which bur for windshield repair should I use? Are carbide burs really better than diamond burs? While the answer may not make a difference in whether you land a customer or not, the questions are worthy of consideration. By the end of this article, I hope to have cleared up any confusion in regard to bur selection.

“When do I need to drill a break?”

We at Delta Kits recommend drilling during the windshield repair process in three situations: (1) those where you are unable to get the resin to flow into the break, (2) to anchor a crack longer than a couple of inches in length, and (3) when a pit must be capped for the injector to seal properly.

In most cases, repair resin will be able to fill the break if you are properly using Delta Kits equipment, 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 of minutes. To me, it is definitely worth the wait if the result is a better cosmetic appearance.

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 into an existing air pocket.

You may also want to drill the end of long cracks. This is to help stop them from running as they are being filled with resin and add additional strength to the completed repair. After drilling the end of the crack (actually about 1/32″ past the end of the crack), follow your slide hammer or spring hammer instructions. Create a mini bull’s-eye and fill it with resin. Do not drill past the first layer of glass. The spring hammer includes a handy depth gauge that helps you drill to the perfect depth for making a mini bull’s-eye.

Finally, if you have encountered an impact pit that is large enough to prevent your injector end seal from sealing properly, you will need to cap the pit and drill a hole through it to allow the break to be filled. You can see this process online in the video titled “How to ‘Cap’ a Pit”.

“What is the best drill bur for windshield repair?”

Now here is something to argue about. You can go a couple of different ways on this one. Many technicians stick to one all-purpose bur, and others take the fly fisherman’s approach, carrying several styles and use the one best suited for the situation. Let’s take a look at your choices.

26020 Tapered Point Carbide Bur, previously known as the FG701 (hole size .047in), – The 26020 is “Delta’s Choice” because we feel it is the best all around bur. It is a fast cutting, extremely durable, tapered bur. It can be used in just about any situation that might come up. The Tapered Point Carbide Bur is the perfect size for drilling the ends of cracks. This is because the tip of the slide hammer fits neatly in the hole. It  “pops” a perfect bull’s-eye nearly every time. Smaller holes will not accommodate the slide hammer. Too tight of a fit can also cause damage to the glass. This is the only bur recommended by delta kits for use with the slide hammer and spring hammer.

26030 Round Tipped Carbide Bur, previously known as the FG2 (hole size .039in) – The 26030 is popular with many technicians because the round head makes it less apt to skip or travel across the glass when you start drilling. The 26030 also drills a smaller hole, which is preferable to many technicians. Although not as durable as the Tapered Point Carbide Bur, the Round Tipped Carbide Bur still outperforms most other burs on the market for most break types. It is not, however, recommended for stopping long cracks.

26065 Long Tapered Point Carbide Bur, previously known as the FG170L (hole size .039in) – The 26065 is great for the technician who desires the benefits of a tapered bur, but with a long narrow point that drills the same size hole as the 26030.

26050 Long Tapered Point Carbide Bur, previously known as the FG169L (hole size .031in) – The 26030 also features a long tapered point, but drills an even smaller hole. The Long Tapered Point Carbide Bur is a great bur for tiny breaks. Especially where a larger drill hole may be very apparent.

26040 Pear Shaped Carbide Bur, previously known as the FG329 (hole size .024in) – The 26040 features a unique pear shaped head that drills the smallest hole of any Delta Kits bur. Many technicians feel the 26040 drills faster and lasts longer than the Round Tipped Carbide Bur. Yet, it provides the skip free qualities that make the 26030 so popular. Testing by Delta Kits indicates the Pear Shaped Carbide Bur is less durable than the Round Tipped Carbide Bur. But, if desiring the smallest possible hole size, the Pear Shaped Carbide Bur is a good choice.

Key points:

As a rule, the smaller the hole size, the less durable, and easier it is to break the bur. Size does matter when you intend to “pop” a bull’s-eye at the end of a crack. The smaller is certainly not better in this instance.

Delta Kits does not sell diamond burs, as carbide burs are far superior in durability and cutting speed. Carbide burs are also much less expensive, although that is not our main consideration.

My opinion: 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 will buy only Fords. The only way to know which bur will best suit your windshield repair needs is to try them.

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