hole saw questions

paulga · Aug 19, 2024

I was looking for some odd sized HSS hole saws with fine teeth - 94mm (for inside cabin wall) and 43mm (for fiberglass on topside), but they have turned out to be difficult to find. Both sizes are available from this Carbide Hole Saw

does this saw make a hole on the fiberglass with edges as smooth as a fine teeth hole saw?

the hole on the fiberglass will need to avoid the plank lines on the outside, and avoid wires and pipes on the inside. once the location is set, the cutting can start from either inside or outside, then switch back and forth as needed.

sean9c · Aug 19, 2024

94mm is only .050" smaller than 3-3/4" and 43mm is only .060" bigger than 1-5/8". You should be able to find both of those in steel. .050" bigger than your 94mm shouldn't be a problem. Drill the 1-5/8" and file it out to 43mm. It's only a boat, it ain't that critical.

paulga · Aug 19, 2024

sean9c said:
94mm is only .050" smaller than 3-3/4" and 43mm is only .060" bigger than 1-5/8". You should be able to find both of those in steel. .050" bigger than your 94mm shouldn't be a problem. Drill the 1-5/8" and file it out to 43mm. It's only a boat, it ain't that critical.

so this type of hole saw does not work well on fiberglass?

1-5/8" is ok, but I only found 4-6 tpi HSS hole saws at this size. could you post a link what you would use for topside fiberflass? as i checked last time it's b/t 3/8" to 5/8" thick and not cored

sean9c · Aug 19, 2024

paulga said:
so this type of hole saw does not work well on fiberglass?

1-5/8" is ok, but I only found 4-6 tpi HSS hole saws at this size. could you post a link what you would use for topside fiberflass? as i checked last time it's b/t 3/8" to 5/8" thick and not cored

That hole saw you pictured would, I'm sure, work great in fiberglass but it's also a lot more expensive than a steel one and since it's likely a one time use why spend the money. I'm my experience any hardware store HSS hole saw would work fine in fiberglass.

Comodave · Aug 19, 2024

When you are going to drill a hole in the hull I put a large rare earth magnet on either the inside or the outside depending on which is more critical. Then go to the other side and take a second rare earth magnet and it will find the first magnet. That way you know for sure exactly where the hole will be and you can check for interference.

Then for the hull you want to drill from the outside because if you drill from the inside when the hole saw punches through it will make some damage in the glass. When you start to drill, drill the pilot hole first, then start the hole saw in reverse and cut through the gel coat. Then put the drill in forward and cut through the glass. This way you will get a cleaner cut. If you drill through the gel coat going forward you may chip the gel coat because the teeth in the hole saw may grab the gel coat and lift pieces up and off.

paulga · Aug 19, 2024

sean9c said:
That hole saw you pictured would, I'm sure, work great in fiberglass but it's also a lot more expensive than a steel one and since it's likely a one time use why spend the money. I'm my experience any hardware store HSS hole saw would work fine in fiberglass.

in my situation i'm looking for the saw that is easiest to use to allow a beginner to nail it, other factors are secondary for now.

How does this Synthetic Diamond Grit Hole Saw compare to the carbide bit in post #1 for fiberglass?

ABfish · Aug 19, 2024

That looks to be a major upgrade over a bimetallic hole saw. I never regret buying a better tool.

jleonard · Aug 19, 2024

I always put blue painter’s tape on fiberglass before i drill. It helps prevent the fiberglass from chipping.

paulga · Aug 19, 2024

Thanks all for your input.

I just tested the clearance in the cabin closet with my DeWalt drill and a 1.5" hole saw. I will have to make an opening in the closet wall to access the hull. Even a 5" opening on the plywood is too small. It would allow the chuck go in, but before the arbor tip could touch the hull, the battery in the handle would have been barred by the wood. searching how to avoid cutting a large panel just to accommodate the drill's handle, I found an angle drill
is this the solution? or is there a way work around?

sean9c · Aug 19, 2024

Those things don't have much torque, that's how they keep them small. It'd likely have enough power for your small holesaw but nowhere near enough for your large.

paulga said:
Thanks all for your input.

I just tested the clearance in the cabin closet with my DeWalt drill and a 1.5" hole saw. I will have to make an opening in the closet wall to access the hull. Even a 5" opening on the plywood is too small. It would allow the chuck go in, but before the arbor tip could touch the hull, the battery in the handle would have been barred by the wood. searching how to avoid cutting a large panel just to accommodate the drill's handle, I found an angle drill
is this the solution? or is there a way work around?

View attachment 157482

RT Firefly · Aug 19, 2024

Greetings,
Extender: 3/8" x 12" Bit Extension

paulga · Aug 19, 2024

RT Firefly said:
Greetings,
Extender: 3/8" x 12" Bit Extension

Thanks.
I bought this 12"x1/2" hex shank extension
my arbor bit is 7/16" and my drill chuck is 1/2"
this extension can adapt to 3/8" - 7/16" shank, while the other 10" extension only adapts to 1/4" -3/8"

DDW · Aug 19, 2024

To answer the original question, almost any carbide saw tooth has less rake (cutting angle) than a steel one. That may make it chip more. The diamond grit one (or carbide grit if you can find it) will often cut a smoother hole in fiberglass, as it is essentially sanding the material rather than ripping it apart, however it will be slow work. The grit will load up quickly so you will be going a very short distance, removing and vacuuming or blowing it clear, then repeating. Fine it you have the time. The Starrett one you pictured has an interrupted rim to help mitigate this, dust has a place to go.

SIBERNUT · Aug 20, 2024

Ever hear the song "Poison Ivy"?
Suggest you have a helper with a vacuum right up next to the cutting, and overhead use mask & glasses. And wash up with cold water, closes the pores.

paulga · Aug 20, 2024

SIBERNUT said:
Ever hear the song "Poison Ivy"?
Suggest you have a helper with a vacuum right up next to the cutting, and overhead use mask & glasses. And wash up with cold water, closes the pores.

Does anchorlube work?
Do you spray it onto the saw grit or the gelcoat and fiberglass?

sean9c · Aug 20, 2024

You don't need any cutting fluid or anything like that. it'll just make a mess. Fiberglass dust might make your skin itch, if you're worried about it use a vacuum while you drill. Though with the big hole I'd have both hands on the drill. On the hole thru the hull if you'd plan to drill from the inside drill a little bit from the outside first just to score the surface. you'll end up with a cleaner hole.

SIBERNUT · Aug 21, 2024

It's not just the skin itch - drilling overhead that stuff is going in your eyes and lungs.

paulga · Aug 21, 2024

SIBERNUT said:
It's not just the skin itch - drilling overhead that stuff is going in your eyes and lungs.

any recommendations?

it seems the safety goggle that the professionals wear is not fully closed on skin, so dust can still get into the eyes from the gap

for the dust masks, I have kn95 without the breathing valve, it can block pm2.5 so should be sufficient

dhays · Aug 21, 2024

paulga said:
any recommendations?

it seems the safety goggle that the professionals wear is not fully closed on skin, so dust can still get into the eyes from the gap

for the dust masks, I have kn95 without the breathing valve, it can block pm2.5 so should be sufficient

View attachment 157524

View attachment 157523

If the goggles were tight to the skin they would tend to just fog up and you wouldn't be able to see. The goggles that you pictured are going to be good enough. You want to stop any falling particles, you don't need to be as concerned with the floating dust for the eyes.

NStenger · Aug 22, 2024

As others have said, running the drill in reverse to cut the gelcoat first is critical to avoid chips.

Bmarler · Aug 22, 2024

Don’t know where you’re drilling but if you can fit one or these it will keep the dust contained.

Amazon.com

paulga · Aug 22, 2024

Bmarler said:
Don’t know where you’re drilling but if you can fit one or these it will keep the dust contained.

Amazon.com

Thanks.
This looks a clever design.

HeadedToTexas · Aug 22, 2024

Sorry if this was already covered, but don’t forget that the hole saw needs to be as deep as the material is thick. Hulls can be thick. Measure twice, cut once, as they say.

hole saw questions

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