Which drill to use for a 1 inch hole

sailcapt340

sailcapt340

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Sep 26, 2008
698
Hunter 340 0 Wickford, RI
I plan on mounting my Standard Horizon Ram4 Remote Mic cable on my pedestal. In either one of the 2 highlighted areas shown here. Both are dependent on easy enough access inside the pedestal. I need to know which drill to use that will cut through the fiberglass and then the plywood backing without damaging the fiberglass itself.
When I had to widen the original VHF mounting hole to fit a small shelf to fill the space, I had a heck of a time just cutting down the edges of the existing hole, probably had dull dremel bits but I don't want to chance damaging the 1 inch round hole I need for the cable end to fit into.
Thank you for the guidance.
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dLj

dLj

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Mar 23, 2017
4,301
Belliure 41 Back in the Chesapeake
It kind of depends upon the precision you need for that 1" size. Not super precise, I've had good luck using Lenox Bi-metal hole saws. You do have to be very careful as you are starting the cut on the fiber glass to get it started nicely. But slow and careful starting seems to work. You also need the depth for the pilot drill to extend into the space you are drilling.

dj
 
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stickinthemud57

stickinthemud57

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Apr 11, 2020
783
MacGregor 26s Scott's Landing, Grapevine TX
A decent quality hole saw from a big box store should do the trick - the kind that fits on an arbor and has a small drill in the center to start and guide the part that cuts the hole. Definitely not a spade bit. Like dLj says, go slow, especially when the hole saw itself first makes contact with the surface. Withdraw the bit and clear the teeth several times during the process. If you see smoke or get a burnt smell, slow down.
 
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Project_Mayhem

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Sep 24, 2018
3,303
Catalina 30 MKIII Chicago
For the absolute best cut, use a new hole saw. I'm partial to the style below for metal and fiberglass, even if it is a Chinese one. Before you start, put some masking tape over the area to be drilled out (can reduce chipping). Drill your pilot hole and reverse your drill to get through the gelcoat, or at least a through a significant portion of it. Once you get at or close to the fiberglass you can use the drill in the normal direction to complete your hole.
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sailcapt340

sailcapt340

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Sep 26, 2008
698
Hunter 340 0 Wickford, RI
The manual states drill a 30mm hole, so just over 1 inch. Once drilled I can fine tune the hole to just fit the cable end in.
I haven’t been up and inside that side of the pedestal in quite a while, but there is definitely more room in there than the other side. I have a horn button, utility plug and on/off switch for the pedestal light on that side.
I‘ll have to remove the tachometer for somewhat easier access and I think the upper location will be better, as the cable end, ferrite core and inside washer will extend about 2 inches long. I don’t believe there will be that much room inside the area near the tachometer.
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,208
Hunter 310 West Vancouver, B.C.
Everything above and be sure to cover with masking tape before starting. Makes the difference between not bad and perfect and that was for a 3-1/2" hole for a windless.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,879
CAL 35 Cruiser #21 moored EVERETT WA
For fiberglass boats, I learned it is recommended that you start to drill the hole with the drill running in reverse. This will be easier on the gelcoat as it is brittle. Once you have the whole started then turn the drill direction around to finish the hole in forward motion. This precuts the gelcoat creating fewer chips.
 
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colemj

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Jul 13, 2004
517
Dolphin Catamaran Dolphin 460 Mystic, CT
Project_Mayhem said:
For the absolute best cut, use a new hole saw. I'm partial to the style below for metal and fiberglass, even if it is a Chinese one. Before you start, put some masking tape over the area to be drilled out (can reduce chipping). Drill your pilot hole and reverse your drill to get through the gelcoat, or at least a through a significant portion of it. Once you get at or close to the fiberglass you can use the drill in the normal direction to complete your hole.
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Click to expand
This. And these hole saws. They are amazing, and the only thing I've found that will cut through fiberglass more than a few times before becoming trash. Cuts through metals like butter also. Follow the above advice about operating in reverse to cut through the gelcoat first, and you won't need any tape to make it clean. Use tape anyway - it's good practice.

Having said the above, if all you need is a single hole and you are sure you won't need to make holes in the future, then a cheap Harbor Freight hole saw will be good for one hole. A more expensive one like a Milwaukee or Lenox bimetal will get you a few holes before being trash.

DON'T borrow a hole saw for fiberglass from a friend. It puts them in a bad situation. I've learned to just say no and accept whatever effect comes. Otherwise, you are just buying the person a hole saw because it will not be returned in good shape.

Mark
 
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dLj

dLj

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Mar 23, 2017
4,301
Belliure 41 Back in the Chesapeake
colemj said:
DON'T borrow a hole saw for fiberglass from a friend. It puts them in a bad situation. I've learned to just say no and accept whatever effect comes. Otherwise, you are just buying the person a hole saw because it will not be returned in good shape.

Mark
Click to expand
This is REALLY good advice!

dj
 
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thinwater

thinwater

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Mar 26, 2011
3,684
Corsair F-24 MK I Deale, MD
If you cannot tolerate a center hole (you are drilling over and existing hole or there is something back there), drill a hole in a wood scrap, clamp the scrap in place, and drill with the pilot drill removed. Just start slow, no problems, I've done this many times. Drilling tile in a bathroom is the classic case. Also replacing through hulls.

Also water to cool the saw, if the hole is more than 1/8-inch of fiberglass. This greatly reduces dulling as well.

Lots of good advise above.
 
sailcapt340

sailcapt340

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Sep 26, 2008
698
Hunter 340 0 Wickford, RI
Thank you all, great help. Still a bit too cold to try to get this done, given where the boat is on the hard. Not a lot of sun hitting it right now. Another week or so. So this gives me time to look at getting what dLJ and Project mayhem suggest. And I completely agree with not borrowing also.
The cold weather was a blessing in running the cables through the boat, wouldn’t have wanted to tackle that in the heat, cutting into the gel coat etc can wait a bit.
Thank you all, again.
 
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