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View Full Version : Drilling square through a bulkhead - is there a jig?



CT
09-01-2011, 09:28 PM
I've got to drill through a 45mm bulkhead to run some plumbing. It will be a holesaw job but I'm wondering if anyone knows of a jig or a trick for getting my pilot hole to go through square on. I was going to cut from both sides, but was hoping for a little better than a calibrated eye and pot luck to get them to line up neatly in the middle.

Cheers
Craig

The-easyrider
09-01-2011, 09:40 PM
Drill through with a smaller pilot hole from one side only. if not sure about going through hold a square against the work surface and keep the drill paralel to it as you drill

Jarrah Jack
09-01-2011, 09:56 PM
The trick would be to do a hole first in about a 35mm piece of timber and clamp that somehow in place where you want the hole. that should act as a guide for the hole saw. If the guide hole is fight then the rest should be good.

Luc
09-01-2011, 10:28 PM
I have a jig into which a drill can be clamped and the jig's base plate will hold the drill perpendicular to the surface to be drilled.

Luc

STUIE63
09-01-2011, 10:42 PM
drill the pilot hole right through . if the pilot drill is not long enough the get a drill that is the same size
Stuie

D river
10-01-2011, 05:44 AM
And remember to sleeve it with condute and sica to prevent any chance of water getting into the bulkhead

finga
10-01-2011, 07:09 AM
Put some masking tape down before you drill too.
That helps with chips in the gelcoat.

CT
10-01-2011, 09:55 PM
Thanks all. Good tips. I've bought a dowel jig that I can use to get a square pilot hole and then I'll use Jarrah Jacks idea of a pre-drilled offcut to guide the holesaw. I'll drill that in the press so I know it will be square.


And remember to sleeve it with condute and sica to prevent any chance of water getting into the bulkhead

I was debating this vs. painting the inside of the hole with resin to seal it and then using sica around the pipes where they go through. The bulkhead should be all glass (no timber). I guess in part it will be determined by how close I can match my holesaw to the pipe diameter.

I'll keep planning and measuring twice!

Cheers
Craig

D river
11-01-2011, 05:37 AM
It depends on the breed of boat but even if it is all glass it'll be hollow and resin without mat will just crack out remember to grind all the glass area properly or any glass work you do will just come apart. If you make your hole a little bigger and sleeve it it'll allow any water that gets there to drain easily to the back of the boat.

deckie
11-01-2011, 07:50 AM
Try to keep away from stress/structural/join areas in glass boats if u can, but here's one guys way....a little more effort but worth it for mine. There's a hundred things u can poke thru as sleeving after drilling but pvc can cut thru wire/cable/fuel lines just as easily as anything else so just make sure its well rounded.
This was a thinner bulkhead and done with a 50mm holesaw so that i could use a couple of standard rod holder caps on 2inch 316 tubing, u can get them at Whitworths or other for about $2.50. They work a treat and no chance of vibration/rubbing causing long term issues to batt cables/fuel lines etc...5 bux for both ends of the sleeve seemed cheap insurance. I had some 2inch tubing already but u can hit the local metal man for an offcut.
If its 45mm and u want it square try glueing/clamping a cpl of small but thick ply offcuts together to make up about 30mm then drill a pilot hole preferably with a drill press or anything to get a vertical/square hole. Line it up to the bulkhead where the holesaw bit will be and glue it fairly solid but not so much u cant get pry it off easy enough. Drill a pilot hole thru for the holesaw then take off the offcut and use the holesaw. Should keeps it pretty square or good enough to square.
Sand out/round off edges and put some epoxy in to seal it up then sand more for a real snug fit and then tap the tubing in with a hammer and epoxy/sika...sika it up and pretty it up if visible and whack on the rod holder caps. Obviously if u dont need a biggish hole go as small as possible and if not a potentially stressed area of bulkhead u shouldnt need to be so anal about sleeving/strength. Definitely seal the hole v well.

CT
16-01-2011, 07:30 PM
Thanks for all the good suggestions. Got the holes drilled yesterday with a combination of dowel jig and home made jig and they went through perfectly square. The was glass and timber in the bulkhead so I sealed the whole lot with resin before adding in the conduits and gluing them into place with resin. Now just the plumbing to go.

Cheers
Craig