Captain Daggett Boat Maintenance Series - Enlarging an existing hole in fiberglass.

When replacing instruments and other mounted items there are often times that the hole needs to be sized up from the existing hole. Doing that is easiest with a hole saw but requires using the following method to properly cut the new hole without damage to the fiberglass from the hole saw "dancing". This technique will allow you to cut a perfect and clean hole every time.

[@alraguc]

I used the same method to drill my bathtub holes bigger for a new surface faucet. Thanks. It worked well. Only suggestion from someone else that helped was to drill in reverse for the complete process since the teeth are less aggressive..

[@pafrazier56]

Genius on all counts. . . I knew the other method and honestly never thought of putting the wood on the surface! Also running the drill backwards. I have to install a 1" drain plug over a ¾" opening and this is the perfect solution! Thank you Captain Daggett! It's why you're the Captain and I'm just a Bilge Boy! Ha!

[@johnalbers8020]

Good idea about drilling a slightly larger hole. It seems so obvious after I watched your video

[@thebluepill1496]

Many thanks Captain. Very concise and informative video.

[@keikikipapa4804]

Thank you so much for this video. Also, glad you mentioned going in reverse, I can see the difference.

[@captaindaggett1934]

Glad it was helpful!

[@Bierdaddy1]

Great video! You were to the point and easy to understand. Do you do any prep work on the fiberglass? Is there any sanding or smoothing after required? Is there a gasket or sealant needed a good fit?

[@captaindaggett1934]

No prep work on the fiberglass other than removing and debris and cleaning the surface with acetone. I use Down Corning 795 or Life Caulk for the sealant.

[@raybates3119]

Great tip!

[@ClinToneCust23]

Thanks!! Great tip

[@mmlamendola4227]

Good tip - I was looking for a decent method to do the same thing in a fiberglass motorcycle fairing

[@captaindaggett1934]

Glad it helped!

[@pierremitham2964]

Another method that works really well is to install the hole saw on your mandrel for the hole you want to cut AND install a hole saw the same size old hole on at the same time. There is usually enough thread on the mandrel to do this. That way the smaller holes aw acts as a guide for the larger hole saw.

[@captaindaggett1934]

That is a good option if you can find the hole saw kit that allows it. Many hole saws do not allow it and often times people only want to spend the money on the size they need instead of the whole kit. But yes, if you have them and they fit that is a really effective and easy way to do it.

[@pafrazier56]

@@captaindaggett1934 I have a stacking set of hole saws for much smaller holes. Wondering however, how can you offset the smaller size so it goes into the existing opening first as a guide? Sounds good in theory but not sure in actual application.

[@bryanzera]

Really enjoying your videos. Could you have clamped the wood in place somehow? I was surprised that bluetape held.

[@captaindaggett1934]

The wood didnt have much stress or pressure on it so the tape was sufficient.