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  #11  
Old 12-24-2012
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They do minimum 1/8th step up last I checked. I don't like dremel tools for things like this, maybe if you have a really thin hull to work with, and an aggressive carbide bit. Otherwise neater and much faster with the right tool for the job imo. As faster points out, no good if you have to move the hole, but otherwise handy.
They are pretty common, Lee valley charges 9$, but I've seen them all over once I knew the name for them.



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Last edited by Jgbrown; 12-24-2012 at 05:51 PM.
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Old 12-24-2012
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Re: Enlarging hole in hull

Would a flapper wheel do the trick?
Cheap and effective for the work I do with them.
Come in different diameters and height of flaps too.


As my post count is under 10 I can't provide a live link sorry.

josco.com.au/newsite/jia/Images/flap_wheels_standard_group.jpg
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Old 12-24-2012
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Re: Enlarging hole in hull

Interesting challenge. Here are some thoughts:
  • If you go with a regular hole saw with a block of wood inside the hull, pre-drill the 1/4 pilot hole. Then turn the pilot bit around in the hole saw so the smooth part of the drill bit rides in the pre-drilled pilot hole. This will give you minimal wandering.
  • The oops arbor looks interesting. I would think the slower turning drill you could find the better. A powerful slow turning 1/2 drill would probably work out better than a fast 3/8 rechargeable jobby
  • The other way to get a nice round hole is to make a template and then use a router with a collar to "trace" around the template. But the odds are low you could easily clamp a piece of wood on the inside or the outside of the hull for this to work.
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Old 12-25-2012
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Re: Enlarging hole in hull

If you don't want to use a dremel then a block of wood would be best. But a good way of doing this is take the 1 1/8th hole saw and drill a plug out of a block of wood. When you remove the piece from inside the hole saw this should make a plug real close to a 1" plug. Might have to sand a little or wrap with tape to fit existing hole in hull. Now mount this 1" plug to a block of wood. Now when you put this into the hole to drill larger it will give a perfect center pilot hole. Greg
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Re: Enlarging hole in hull

I had to do the same thing last season for a pump out fitting. I had used the wrong hole saw, at least I used one too small rather than too large. I ended up using a rotary rasp on a power drill.

http://www.sailnet.com/forums/attach...1&d=1356466075

Going very slow and keeping the drill at a right angle to the work suface allowed me to enlarge the hole in just few mins. Make sure you have drawn a very clear border to work out to, stop just shy of the line then finish with a small sanding drum or sandpaper wrapped around a dowel. Again, keeping the tools at a 90 degree angle to the hull will be key for this project.
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Old 12-25-2012
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Re: Enlarging hole in hull

Oopsie arbor: damn, I need to buy another neat new tool I never heard of before!

The block of wood to allow a new hole saw with pilot is the conventional way to go, but you can also often skip that by running the new larger hole saw IN REVERSE to score the hull and get a ring started. If you do that very carefully, once you have the ring started you can go into forward and just cut through.

Of course, the block of wood and new pilot hole eliminates a whole world of possible errors. Use a hot glue gun to attach it, and you can pop it off easily afterwards.
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Old 12-25-2012
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Re: Enlarging hole in hull

Quote:
Originally Posted by baboon View Post
I had to do the same thing last season for a pump out fitting. I had used the wrong hole saw, at least I used one too small rather than too large. I ended up using a rotary rasp on a power drill.

http://www.sailnet.com/forums/attach...1&d=1356466075

Going very slow and keeping the drill at a right angle to the work suface allowed me to enlarge the hole in just few mins. Make sure you have drawn a very clear border to work out to, stop just shy of the line then finish with a small sanding drum or sandpaper wrapped around a dowel. Again, keeping the tools at a 90 degree angle to the hull will be key for this project.
I've put in new holes...





and enlarged holes very quickly with a carbide bit. I have a lot of air at home to use one but not so much at the boat. We were going to do so much work there that we did buy a $100 portable air compressor to use there on 110. It won't run long, but I don't need it that much.

The other thing I like about the air tool/carbide bit is that...



...I can get up into places and enlarge holes or make them where it would be very hard to do with another tool.

I do think I'll make an oops arbor tomorrow though. I was going to order one, but $8 shipping on a $8 tool made me think twice. It should take less than an hour to make one. I don't get paid much for my time so I'm good there ,

Sum

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Old 12-25-2012
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Re: Enlarging hole in hull

I echo the dremel recommendation. Have done this many times. Trace the circle and dremel out to the trace. A dremel is an incredibly precise tool. Far more precise, and less risky, than a hole saw IMO. I use hole saws to start fresh, but to just enlarge, I'd have this hole perfect in just a couple minutes. Easy peasy.

Like so much, it's really just a question of what makes you comfortable, and how you are willing to fail!
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