DRILLING COMPASS HOLE

[Bill Armstrong]

Adding a bigger, bulkhead mounted, compass. Current hole is 4" and now I need 5". The compass hole is directly opposite the wires entering the electrical panel. Need advice as to which tool(s) to use. After scribing the circle, my first thought is to drill small holes completely around the circle, mask it, then use a super small,
sharp saw blade. Has anyone done this? Appreciate any suggestions. Thanks. Bill....



meislandbill@yahoo.com

[Dana]

When I converted from a Aquameter Saturn to Gemini compass. I joined the hole "dots" ...if it was an original hole I would have generally use a hole saw.



darenius@aol.com

[Larry DeMers]

Bill,

Well you could nibble it away, using the method you highlighted, or something similar. But if the hole edge is to be close to round and smooth, then you will have to redrill the hole. Here, you can take a piece of 1x6, and temporarily tack it into place behind the panel you want to redrill. Sticking it down witha couple dabs of 5 min. epoxy, you should be able to pop it free after this all done, as the 5 min. epoxy is pretty brittle and should shatter easily. Get a hole cutter for 5 inches. I use (very carefully) a flying head cutter mounted on my variable speed drill. The idea is to drill a hole in the wood, at the exact center of the existing hole. Insert the flying head cutter (adjusted to 5 in.) and begin to rotate the cutter slowly. This can be a dangerous proposition, so be careful. It will create a scratch int he fiberglass, then the scratch gets widened and deepened until the fiberglass skin is cut through.
I cut our fireplace stack (also a 5in. hole) with this tool and it takes some careful effort toget it done right, but it does work out.

Cheers,

Larry DeMers
s/v DeLaMer
Cape Dory 30

Adding a bigger, bulkhead mounted, compass. Current hole is 4" and now I need 5". The compass hole is directly opposite the wires entering the electrical panel. Need advice as to which tool(s) to use. After scribing the circle, my first thought is to drill small holes completely around the circle, mask it, then use a super small,
sharp saw blade. Has anyone done this? Appreciate any suggestions. Thanks. Bill....

demers@sgi.com

[Richard Woolson]

Adding a bigger, bulkhead mounted, compass. Current hole is 4" and now I need 5". The compass hole is directly opposite the wires entering the electrical panel. Need advice as to which tool(s) to use. After scribing the circle, my first thought is to drill small holes completely around the circle, mask it, then use a super small,
sharp saw blade. Has anyone done this? Appreciate any suggestions. Thanks. Bill....

To add on to Larry's method a bit,...after you have scribed the outer circle with a fly cutter (which you might want to do turning the drill by hand) switch to a hole saw. The fly cutter is seriously out of balance by design and is intended for use on a drill press.

To find the center of your backing plate, scribe several diameters across the hole at various points around the circumference, then average their intersections.

Good Luck!
Richard W.



richwools@netscape.net

[SLOOPJOHNL]

you may want to rotate that hole saw backwards a few revolutions to get a cut started in the fiberglass, then go forward. this may reduce the chipping of the fiberglass. light pressure helps also. some people tape the fiberglass but that tends to gum up the saw blade.

Adding a bigger, bulkhead mounted, compass. Current hole is 4" and now I need 5". The compass hole is directly opposite the wires entering the electrical panel. Need advice as to which tool(s) to use. After scribing the circle, my first thought is to drill small holes completely around the circle, mask it, then use a super small,
sharp saw blade. Has anyone done this? Appreciate any suggestions. Thanks. Bill....

To add on to Larry's method a bit,...after you have scribed the outer circle with a fly cutter (which you might want to do turning the drill by hand) switch to a hole saw. The fly cutter is seriously out of balance by design and is intended for use on a drill press.

To find the center of your backing plate, scribe several diameters across the hole at various points around the circumference, then average their intersections.

Good Luck!
Richard W.

[Dan]

I have the same problem - need to go from a 4" to 5" hole to add a compass. I can't center the new hole exactly on the existing one as my knotmeter is directly above - the new hole has to extend downward. I was thinking about using a jigsaw or reciprocating saw with FG blade. Wouldn't come out as clean or perfectly round as a hole saw, but the cut will be completely covered by the compass. Is this a bad idea?

[Olli Wendelin]

Bill,

I have done similar jobs by routing free hand using a Dremel tool. Both on the aft cabin bulkhead and the foredeck. Just practice a little beforehand. This has been my handiest tool for getting in tight places or doing odd shapes.

Olli Wendelin
BLUE MOON
Charleston, SC



wendelin@spawar.navy.mil

[Neil Gordon]

>>The compass hole is directly opposite the wires entering the electrical panel.<<

Is the compass more than decorative? I would think there'd be significant interference from the wiring. Most boats I've seen with bulkhead mounted compasses have them on the side away from the wiring.


Regards, Neil
s/v LIQUIDITY, Boston
CD28 #167



neil@nrgordon.com

[Lou Ostendorff]

Hi Bill and others;
I did this very thing when I was installing a 12v accessory plug...the first hole I cut (with a Forstner Bit) was too small for the assembly...so I took a piece of 2X4 and glued a dowel into it that just fit in the hole I cut. I then temporarily fastened this to the backside, with the dowel fitted, and flush, in the hole...from the front, it was a simple matter to rebore the hole to the correct size. I was going from about 1" to 1 1/4"...a little smaller than your project, but the principle is the same; cut a circular pattern to fit the old hole, fasten it to a 2X4 or backup plate, then recenter and drill the correct size hole. The pilot hole is important because it keeps the holesaw or bit centered. If you try to do it freehanded, the cutter may (probably) wander all over the fiberglass, making a mess of things...Good Luck!
Lou Ostendorff
CD25D Karma
Hailing Port "Oriental, NC" ('cause I like the name)



louosten@ipass.net