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Old 20-09-2010, 15:05   #1
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Question How to Drill Parallel Holes ?

My current project is removing all the deck fittings, drilling out the holes a good bit larger, and filling them with epoxy. This is what I mean:

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Some of the fittings have backing plates that I would like to re-use.

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HOW does one drill parallel holes? I can't even do it when the backing plate has two holes. And everything curving and sloping doesn't exactly help.

As an aside, less than three years ago I paid a rigger to set the boat up for me to single-hand and he put Starboard backing pads under the blocks, deck organizers and clutches to raise them up. Most of those bolts were leaking! The Starboard came off the deck and fittings so easily I think the sealant just couldn't keep hold of the starboard well enough to keep water out. Now I've got teak backing pads added to this project list.
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Old 20-09-2010, 15:09   #2
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Some drills have levels built in. Might help with the "parallel holes", if I understand you correctly.

Starboard is not a good material for backing plates. Nothing sticks to it and it compresses all too easily. Ask me how I know (yep, a professional shipwright)!

Doesn't rot, though :-)

Bill
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Old 20-09-2010, 15:28   #3
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Make a pilot Jig using 1/2" ply. If its a curved surface you can apply that to the jig easily without doing any "trial and error" damage.

Thats what I would do at least, but I tend to over-complicate things.
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Old 20-09-2010, 15:40   #4
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The only way I know to drill parallel holes regardless of the surface slant or curve is to use an industrial rig that is set up on an Ibeam and can traverse and drill down. Each time it is used it must be reset to what ever datum you are using. I've used them while working as a millwright. I suppose if one were to set up something similar with wood beams and a drill mounted in a cradle, it could be done.

To use a level would require some sort of wedge on the drill if the hole was to be off axis since the level will only show horizontal and vertical. This way you could have all the holes at the same angle in one plane. Keeping them from pointing at each other is a trick I haven't tried yet for manual drilling. I would expect the best you could do is measuring from a fixed vertical surface at two points, one being the tip of the drill, the other the far end of the drill motor itself. To do that you would need to know how thick the drill motor is so you can subtract half that from the distance. Measurements at the drill tip would be X-half the diameter of the drill, measurement at the drill motor would be X- half the thickness of the drill motor at that point. This way you would be able to keep the drill axis parallel.

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Old 20-09-2010, 21:24   #5
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Hi, thanks for your responses.

Bill - Even if I was able to rig a bulls-eye bubble level to the drill (for drilling vertically-ish) I have my doubts about the level's accuracy and being able to maintain the drill position with the drill vibration and boat moving with the wind and wakes. The holes in the backing plates are not over sized - if one of my holes is off by 1/8" the backing plate won't go on. And a level won't help with horizontal positioning when I drill the 54 boltholes for the opening ports. (Starboard compresses easily?! I would have never guessed - and now I have some to experiment with!)

Sabre - you think like I do, I know exactly what you are talking about. I've been mulling this over for months and never could get past any sort of mobile drill press for the drill concept.

Patient - A jig! Ah, the wheels are starting to turn. I'm thinking make a jig out of a 4 x 4 block of epay (or whatever that really hard wood is called). I could lay a piece of plywood over the area to drill, use Sabre's idea of wedges to keep the plywood tangent to the deck, and use the backing plate as a template. That would work. But it sounds a lot more complicated than "using 1/2" ply". I can't visualize your idea at all is there any way you can describe it?

Priscilla
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Old 20-09-2010, 21:53   #6
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Small hole saw maybe?

If I understand correctly what it is you are trying to do, would using a small hole saw with a pilot bit not work? If the pilot bit is the same size as the hole, or larger, it should make the hole saw track perfectly perpendicular to the surface without having to fabricate jigs. Cut the holes just deep enough from the outside to get thru the core, but not the bottom layer of glass, then use heavily waxed or greased bolts thru the backing plates when pouring the epoxy to make sure the holes line up correctly on the outer surface. Duct tape or similar will hold it in place. The epoxy won't stick to the bolts this way and will remove easily after the epoxy sets without having to re-drill the holes. I have done this on balsa cored curved cabin tops to mount radar pedestals and antenna mounts, worked fine for me.
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Old 20-09-2010, 22:13   #7
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I am not sure if you are trying to drill perpendicular to the outside surface or vertical to the boat centerline.

I think you also want a "group" of holes to be parallel with each other.

There are lots of different type of drill guides out there. This one has a drill stop and adjusts on one plane. There are fancier ones that adjust in two planes as well.


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Old 20-09-2010, 23:15   #8
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Doing some work currently (glass ,Kevlar & foam). Pre- drill PVC rod. decore to expose bottom layer & glue PVC.(ruff up the surface of the PVC rod) Intend to fit helicoils on top section & tap the rest of the PVC rod. Screw from top & fit bottom plate with nuts. One man job to to & undo.The PVC is the spacer to prevent compression as well. Seal top plate. Completely water tight job.
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Old 21-09-2010, 01:09   #9
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Using a drill press, dill a hole the diameter you want though a piece of wood that has been cut perpendicular to the dill axis. This then becomes your drilling guide. Aline over the hole you want to drill, start slowly and you'll do fine. This simple rig will drill a hole perpendicular to your work.
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Old 21-09-2010, 01:21   #10
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Drill your holes as best you can and measure the resulting holes by paper rubbing. Then get new backing plates made. That will probably be easier and quicker.
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Old 21-09-2010, 21:03   #11
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Eureka

Thanks for the replies!

Mintyspilot - the backing plates are already there, if I can't get the holes just right then washers are perfectly adequate. I'm not putting the headliner back and my boat's increasingly Mad Max look is starting to freak out my husband a little bit - those pretty backing plates allow me to claim the Shabby Chic look.

PAR - that was the idea I came up with last night, and it will work great except when the holes are spread over a curved surface. And then there is the part about getting the hole drilled perpendicular through the guide in the first place.

bill good - very cool! Too much work for the current project, but I will keep it in mind for the future.

Mi2ndwind - that was how I did my project-from-hell jib sheet tracks. Hole saws don't work so well on fiberglass - the teeth are too big, and fiberglass wears everything out pretty quick, I use a 3/4" drill bit, which makes a big enough hole to easily pick out the wet or rotten core around the inside of the hole, and also allows the epoxy to extend under the deck giving more compression strength like bill good's PVC pipe method.

For the jib sheet tracks I did three boltholes at a time, and my first try was the way you described except I used softwood dowels coated with mold release wax. Thank goodness I was able to drill out the dowels without enlarging the holes. My second try I listened to a friend and tried plastic drinking straws. I won't be listening to him any more. I didn't really want the holes threaded, and after the waxed dowels not working no way was I going to try a waxed bolt. I called the West Epoxy tech support and they said to use slick box tape wrapped around a dowel. It worked! Except for the part that the epoxy makes the tape unstick from itself and start unrolling in the hole.

So NO, I am not going to do it your way again. (What kind of wax did you use?)

Ex-Calif Moderator Person - THAT'S IT! THAT'S THE THING! Someone told me about this device several months ago and I couldn't find it anywhere because I didn't know what it was called - I kept describing it as a portable drill press type object and that gives all the wrong returns in searches - it is a drill GUIDE. I made this post because I finally decided that thing did not exist - and THERE IT IS!!! I just looked it up on McMaster-Carr and they have that exact one for $40 - that's reasonable, tomorrow I'll shop around and see what is out there. Thank you thank you thank you!

Priscilla
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Old 21-09-2010, 21:12   #12
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May have made it sound too hard!! will try to collect pictures. It would not add 5mins to the over all job if material was at hand.
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Old 21-09-2010, 21:22   #13
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Consultancy Bill:

Googling Drill Guide = $1
Pasting image on CF = $3
Knowing it's called a drill guide = $956.02

Cheers!

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Old 22-09-2010, 10:33   #14
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"(What kind of wax did you use?)"
Plain white paraffin (Ball canning wax) works very well and being white, you don't notice if a little smears on something. Or you can buy a toilet bowl seat ring for about $3 in any hardware store, that's a generous piece of yellow bee's wax, which is easier to smear and work by hand. Much cheaper than bee's wax candles.<G>
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Old 22-09-2010, 11:56   #15
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As I understand the problem is that you want the holes from your existing backing plates to line up with the holes in your hardware? Will the backing plates stay where they are and be held in place while you do the drilling?

The drill guide will work on a flat surface. Are you going to use your backing plates in place as your flat surface?

That's a hard one but I think the idea of a jig prepared on a drill press is a pretty good answer. I'd use thick plastic for the jig and after the first hole is drilled run a bolt through and bolt the jig, the backing plate and hardware in place (dry fit) then drill the remaining holes.

I'm going to be doing the same thing eventually so would like to know how it turns out for you.

kind regards,
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