Drilling into Fiberglass with a hole saw. WARNING

[freddo411]

Today I learned that fiberglass is really tough stuff.

I was using my 18v Dewalt drill as a 1" hole saw. The hole saw has an approx 1/4 centering bit, that enters the material first.

Surprisingly, after I started slowly, then ramped up to high speed, the centering bit got part way into the fiberglass and then suddenly seized up, causing the drill to torque violently out of my grip. The force was great enough to shatter the hardened steel of the bit.

Upon reflection, it appears that the bit is too good at biting into the material. A slower approach, slicing less deeply into the material yields better (less violent) results. I accomplished this by using the drill on a quite slow speed.

The hole saw blade didn't seem to mind higher speeds.

[Darwin Maring]

Placing Masking tape over the spot you will drill tends to keep the edges smother.
Always wear a dust mask because of the GLASS Dust.

[Earl E. November]

Cocking the drill or breaking through probably had more to do with the catching and binding than the bit did..

Once the saw started cutting the larger diameter tends to keep things squared up.

But then that is drilling with a hand drill.

[Sue and Henry]

Hum. So instead of hiding a little portable air conditioner in the closet and venting out the wall I should cut a hole in the plastic window instead. Thank you for the heads up!

[freddo411]

Sue and Henry:

You can cut through the 'glass, I cut three holes for water, electric and lights. Just watch out and go slow as needed. ;-)

[Eddie Longest]

When using a hole saw on vinyl siding and thin fibreglass run the drill in reverse. The material is soft enough to be cut and the drill won't grab.
Eddie

[Sue and Henry]

Thanks Fred, Natalie and Eddie - so much to learn!

[Ron in BC]

To put to rest any fears people might have gained from this post I have to say that I've being working with many fiberglass projects, including large fiberglass boats all of my adult life. The event described has never happened to me and I've drilled thousands of holes with standard bits and hole saws. As has been mentioned sometimes a bit will grab as it breaks through the bottom of the hole but that's true for many materials.

So I'd say, if you have a hole to drill, do it without worry, it's easier than drilling some other materials.

One trick I do for using handheld hole saws is: use a 3/16" bit or whatever size the bit is in the hole saw and drill the hole. I then use the hole saw with a 3/16" smooth rod. There is less danger, when drilling freehand, that the drill bit will work sideways and make the guide hole sloppy and provide less guidence for the hole saw. Hope that makes sense

Ron

[Ed Harris]

Originally Posted by Eddie Longest

When using a hole saw on vinyl siding and thin fibreglass run the drill in reverse. The material is soft enough to be cut and the drill won't grab.
Eddie

Exactly,running in reverse will prevent blowout on the back side.