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Old 12-09-2013, 09:33   #1
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Cutting Clean-Out Port in Black Iron

My 1967 Rawson 30 Ave del Mar has two custom-built black iron fuel tanks that were installed in New Zealand years ago. When I started getting the boat back into sailing shape last month I decided to bypass these with a temporary exterior tank instead of fighting with sediment and possible corrosion.

As she and I are settling in I would like to see if the permanent tanks are viable or not, although a thread of the merits or lack thereof on black iron is not my goal. As these tanks do not have clean out ports I was thinking of cutting holes for a Seabuilt access plate system [ Seabuilt - Access Plate Systems ] that would allow me to examine the tanks' interiors. Then, if I am satisfied, I can spend the money to buy the access ports.

I am pretty mechanically adept and do most of my own work, but I have no idea how to cut a clean, round hole in black iron. Thoughts? Advice?
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Old 12-09-2013, 09:37   #2
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Re: Cutting Clean-Out Port in Black Iron

I dont have your answer but hope you get one! I had a 74 Rawson that I sailed extensively... just curious, where are the tanks located in yours?
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Old 12-09-2013, 09:39   #3
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A hole saw will cut a nice round hole. If the cut circle falls in a magnet will pull it right back out.
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Old 12-09-2013, 09:45   #4
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Re: Cutting Clean-Out Port in Black Iron

Hole saw would probably be your cleanest hole, if you can get one of those magnetic drill press stands, that would probably be the best of all worlds, don't forget the lubricant.
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Old 12-09-2013, 10:02   #5
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Re: Cutting Clean-Out Port in Black Iron

These tanks are located under the cockpit -- to port, slightly forward and closer to the cabin, and to starboard further aft.

I am looking at a 6"-8" cut, which I thought might be bigger than a hole saw could handle.
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Old 12-09-2013, 10:08   #6
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Re: Cutting Clean-Out Port in Black Iron

Before you do any cutting, will you be able to completely (as in being able to access all the corners, up and down) clean the tank afterward? Whichever size access port you cut, all the detritus from the cutting will fall into the tank, and be sure the port will let you get your whole arm in.

For cutting the hole, I'd use the scribe and a string trick to get my circle the size I chose, then drill a hole just at the inside of the cutting line that will accommodate the right sabre saw (jig saw) blade, and carefully cut along the line. Carefully control the saw, and lubricate the cut. A little work with a file will smoothe the edges. Even if you chase the blade with a vaccuum, some little iron bits will fall inside.
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Old 12-09-2013, 10:46   #7
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Re: Cutting Clean-Out Port in Black Iron

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Originally Posted by j-hood View Post
My 1967 Rawson 30 Ave del Mar has two custom-built black iron fuel tanks that were installed in New Zealand years ago. When I started getting the boat back into sailing shape last month I decided to bypass these with a temporary exterior tank instead of fighting with sediment and possible corrosion.

As she and I are settling in I would like to see if the permanent tanks are viable or not, although a thread of the merits or lack thereof on black iron is not my goal. As these tanks do not have clean out ports I was thinking of cutting holes for a Seabuilt access plate system [ Seabuilt - Access Plate Systems ] that would allow me to examine the tanks' interiors. Then, if I am satisfied, I can spend the money to buy the access ports.

I am pretty mechanically adept and do most of my own work, but I have no idea how to cut a clean, round hole in black iron. Thoughts? Advice?
Say, are you not the same Rawson that we met in Tassie years ago -- like 1995? IIRC you left her on the hard at DSS for a while, then departed toward the Horn solo. Stretching the old memory, but is Jamie the name? Ann and I were still sailing in the original Insatiable (old one-tonner) then, and I think that we met in Port Arthur...

If so, I'd love to know how your ambitious passage worked out... and glad to have you here on CF.

Cheers,

Jim
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Old 12-09-2013, 11:03   #8
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Hole saws do come in the size you listed, but are a bear to control. If you go this route rather than the jig saw route, I would recommend a cordless drill as opposed to a plug in one. The cordless will stall before breaking your arm. The best drill for this job would be a mag base drill press, these can usually be rented.
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Old 12-09-2013, 11:28   #9
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Re: Cutting Clean-Out Port in Black Iron

John, you don't mention what gage the black iron is in the tank construction, so this may not help... There is a tool called a nibbler that is used in sheet metal work. It has a "snout" that incorporates a tiny shear, driven by hand or a small motor, and it works by taking tiny "bites" from the material. They make a perfectly clean cut and generate no swarf, and some models can cut up to around 3 mm steel stock. I should imagine that they can be rented, and would make a good solution to your problem.

Cheers,

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Old 12-09-2013, 11:29   #10
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Re: Cutting Clean-Out Port in Black Iron

Quote:
Originally Posted by j-hood View Post
My 1967 Rawson 30 Ave del Mar has two custom-built black iron fuel tanks that were installed in New Zealand years ago. When I started getting the boat back into sailing shape last month I decided to bypass these with a temporary exterior tank instead of fighting with sediment and possible corrosion.

As she and I are settling in I would like to see if the permanent tanks are viable or not, although a thread of the merits or lack thereof on black iron is not my goal. As these tanks do not have clean out ports I was thinking of cutting holes for a Seabuilt access plate system [ Seabuilt - Access Plate Systems ] that would allow me to examine the tanks' interiors. Then, if I am satisfied, I can spend the money to buy the access ports.

I am pretty mechanically adept and do most of my own work, but I have no idea how to cut a clean, round hole in black iron. Thoughts? Advice?
I have some photos of the job I did copying the Seabuilt system with my aluminum tank, post #38, you can see it here-
Diesel Tank Cleaning?
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Old 12-09-2013, 11:32   #11
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Re: Cutting Clean-Out Port in Black Iron

Great stuff so far, thanks. Unsure as to the thickness of the iron at this point.
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Old 12-09-2013, 12:02   #12
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Re: Cutting Clean-Out Port in Black Iron

A few observations from my somewhat limited experience restoring old cars. First things first, I assume the tank will be purged with water or an inert gas. This is more important with gasoline than diesel but you could still get one hell of a fire going if you got a good spark in the tank. Diesel starts hard but burns pretty hot once it gets going. Second, I am not sure a nibbler is a good solution I have only seen them used on thin sheet metal and depending on the type of iron it may be too brittle to be cut in that manner. I would stick to a hole saw or jig saw if I was doing it. A cordless drill will eat batteries like crazy cutting with a hole saw that large, it can be done but it will take time. I would use a good corded drill with a handle down by the chuck. Run it slow with lots of cutting oil and you should avoid binding. Also to catch shavings you might try a bunch of wheel grease around the blade instead of cutting oil. You'll make a mess, but it should catch all the shavings. A good cleaning and a magnet in the tank should catch the rest of the contamination.

Tom
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Old 12-09-2013, 12:13   #13
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Re: Cutting Clean-Out Port in Black Iron

Having the flat space on top of a tank to run a jig saw could be a real issue. Few tank installs will have the room.

Issue with hole saw on sheet metal is when part of saw cuts through in one section of circle. Hole saw can jam up and twist your arm off, plus bugger up the hole. The bigger the hole the harder it is to do. Drill press type approach would be great if you have that kind of tool available.

Sheet metal nipper to cut circle (pre-scribe with metal tipped compass), then smooth out with a Dremel tool might be the way to go. Mask area off before grinding (like you were going to spray paint) to keep iron shavings/dust from getting under the floor.

Would need nippers similar to these:
The Official Site of Wiss Brand Cutting Products
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Old 12-09-2013, 12:34   #14
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Re: Cutting Clean-Out Port in Black Iron

Do a search, I describe cutting inspection ports into stainless using a high-torque jigsaw from Porter-Cable
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Old 12-09-2013, 12:38   #15
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Re: Cutting Clean-Out Port in Black Iron

I assume we are talking a 6 or 8" diameter hole. Forget a hole saw for that. You would need a big 1/2-3/4HP drill for that. They are dangerous! and big. alot of power there. Jig saw with the right blade may work. iron is pretty abrasive, I guess you would need a carbide hole saw? or several high speed steel ones.... big $.
I knew a guy who lost a finger and severely damaged another one using one of those big drills. The 3/4" drill jammed, the drill motor spun immediately wrapping the cord around his fingers and the trigger, couldnt stop it. twisted on finger right off. yuck.
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