Lumitec Minute Expert: Drilling & Screwing Fiberglass

If you're like us, you've mounted a lot of things on your boat over the years and had mixed results. We're here to give you some tips that will help you mount like a pro.
You want to get that new GPS or fish finder on your boat and get on out there! So you grab your drill and start drilling right? Not so fast! If you go in to the fiberglass with a regular twist drill a number of things can happen:
-chipping from the drill bit itself
-Gelcoat chips away during screwing
How do you get around it?
-start with a countersink bit. Gives a nice, clean start to hole and locate it accurately.
-Next, pick out the bit that will go through the material for your screw. Make sure you are sizing your drill bits to match your screws.
-Screws have major and minor diameters. You want to start with a drill bit that's about 50% between the major and minor diameters.
It's critically important when drilling & screwing into fiberglass to select the right bit size, start with a nice counters

[@scdrescher1]

Way more than I needed but absolutely worth the watch. Thanks for sharing!

[@MediaFilter]

This guy is an excellent, well-spoken teacher.

[@KMT15]

You can also use a normal drill bit in reverse to get through the top layer of gelcoat without chipping it

[@Beenthere2xs]

This was excellent advice! I had to drill holes in my fiberglass ladder to attach extension legs and the countersink bit was exactly what I needed. Thank you!

[@mikesobera5204]

Great video and advice! Seeing all of these Lumitec videos have convinced me these are the best lights to purchase for my boat. Awesome customer resources to help DIY'ers.

[@dustins3400]

Thanks for the tips - I'm doing some work on my boat this weekend and that will come in handy.

[@juliejoyner1117]

THANK YOU! I really appreciated the information about the mechanics of a screw and how/why to pick the correct bit.

[@familykeepersca]

thank you very much, solved my questions about drilling problems on fiberglass.

[@leandrozerbo8034]

good advice! I'm installing name lights on a 50+ million dollar yacht .. So im soaking all of this in like a sponge !!

[@rmanicom]

Nice shot video and answered my question too

[@ReelinTension]

What counter sink bit would be used for # 12 x1.5 stainless screws

[@mfawls9624]

Didn't answer my question...but...gave me the necessary caution as far as simply drilling into fiberglass and chipping. I'm trying to attach a porch railing to a fiberglass (I think composite and fiberglass) column. Pulling off the railing chip the column and I've repaired that with Bondo but don't want further damage.

[@terjelundsten5193]

Thanks for your nice tutorial. Could you elaborate slightly on the 50% between part? Is that closer to the minor or closer to major diameter, as I suppose 100% between would be in the center between the two...

[@LumitecLighting]

Sorry for the later response on this. Got missed! The 50% refers to the center point (approx) between the bit cutting edge and the main shaft of the bit.

[@hepper7]

I want to screw a 1/2 “ piece of plywood onto fiberglass. I was told to use a # 8 countersink bit first. What kind & size of screw should i use to secure it?

[@louie4445]

I want to add new chrome trim moldings to my cloth top on my Lincoln town car. What tools will I need exactly? That way when I go to Home Depot or Lowe's I can just have a list ready.

[@LumitecLighting]

Luis, sorry but we have no experience with Lincoln town cars and therefore can not suggest which tools would be required for your project.

[@LuckyBuff4949]

What works for me. Drill two sizes smaller than the screw size.

[@owengerig]

not sure how to calculate bit size. (50% of major minor doesnt really make sense to me)

[@D3nn1s]

Basically the average. So if the threads are 5mm and the solid core of the screw is 4mm youd use 4.5mm

[@bentleynut1648]

Good video but it would have been useful to provide a chart of recommended drill size vs screw size

[@LumitecLighting]

Bentley, there is a graphic (not a chart) on this reference page link beside the video that illustrates the drill bit size selection that may be helpful. lumiteclighting.com/minuteexpert/

[@Z-Ack]

Screwing fiberglass sounds painful..