Tapered burs, round burs pear shaped burs and dozens of other shapes are available in a variety of different sizes. For instance, round burs are available with tip sizes ranging from .020" to .177". The shape and size that you select is largely a matter of preference, however there are a couple of things to consider.

It should be noted that there are sometimes huge differences in the quality of burs so you cannot go by shape alone. A poor quality bur will not work well regardless of the shape or size.

Tapered burs typically drill faster and last longer in the tests that we have performed. Care must be taken to avoid skipping and binding in the hole.

Round burs are typically a bit slower and don't last as long but there are few problems with skipping or binding in the hole.

Pear shaped burs such as the FG329 are a happy medium for many people. They offer relatively fast drilling and good durability while minimizing the chances of skipping or binding.

I highly recommend a larger bur such as the FG701 if you are creating bullseyes by tapping in the drill hole with a probe. The Delta Kits 77-7G works very well for this purpose, creating a perfect little bullseye nearly every time. We have experimented with many burs and many different pointed tools to create bullseyes, and this seems to be the best combination. Using a smaller tool often creates a small star break and using a larger point in a small hole often creates surface damage. Not everyone will agree on this, but that was our finding after some extensive testing.

Although there are literally hundreds of combinations of bur shapes and sizes that are offered on a special order basis, Delta Kits and other suppliers generally only list those that are the most popular and have been found to perform the best for windshield repair.

In our testing, carbide burs are more popular than diamond burs, because they work well without the use of a cooling fluid, drill faster, last longer and cost less.

My advise is to try several shapes, sizes and brands. You will probably find one that you are much more comfortable with than any other. That's the one for you. As I said, it is really a personal preference in most cases.

Good luck,

Brent Deines
Delta Kits, Inc.

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