Stainless steel backing plates, thoughts, where to buy? - Page 2 - SailNet Community
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post #11 of 34 Old 02-07-2012
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If aluminium would do, I would use it. It is vastly easier to work and is more forgiving. It does not hold its finish well, but you will be able to make those backing plates with a drill, a jig-saw and a file.

Stainless is very hard indeed, and very difficult to work it.

Also, stainless, it is very prone to corrosion cracking, particularly when oxygen-depleted, and the very hard nature of it will mean that it propagates cracks easily.

It is a pretty material, but I am suspicious of it.
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post #12 of 34 Old 02-07-2012
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You can get all the stainless shapes at a number of online metal dealers for a good price. Use 304 or 316. All can be welded very nicely with "Missileweld" rod with a little practice. As far as getting a high polish, if that's what you're looking for, it is easily done with a da and some fine paper. Sandpaper can be obtained down to 12000 grit. Soapstone will give you a glass finish. I personally do not know why everyone thinks stainless needs to be polished to a high degree. Tests of surface corrosion between polished/matte/304/316 in sea water environments show little difference. I fabricated all new rigging for my boat; new chainplates, masthead, bow plate, and lots of other parts out of 304 and 316. Some I polished, some not as much. Have seen no appreciable difference.

The tools you need are an abrasive chop saw(or metal-cutting band saw), a hand grinder, a grinding wheel, a good drill/drill press with cobalt bits, a flat belt sander, a da sander, some elbow grease if you want to obsess over polishing, and a stick welder with D.C. capability. If you have a gas-shielded welder, all the better.

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post #13 of 34 Old 02-07-2012 Thread Starter
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Really I want to polish it because it'll be next to another polished plate! I have access to all those tools apart from the welder, which actually I don't need as I'm just making flat plates.

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post #14 of 34 Old 02-07-2012
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A waterjet place is your friend as i did the whole boat including the SS mast step and electric pannel out of drops (leftovers from big jobs) for zero as they like me
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post #15 of 34 Old 02-07-2012
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Really I want to polish it because it'll be next to another polished plate! I have access to all those tools apart from the welder, which actually I don't need as I'm just making flat plates.
Sure, if it's next to something you need to match. The flat plates are easy to polish. The pieces with right angle welds are a pain. I smoothed mine down to, I think, 600 grit, not real shiny but smooth. I have a small 3" da sander that works well. Also used the old plates for some really good backing plates. I moved the shrouds outboard and increased them from 1/4" X 1 1/2" to 2". Was also able to slightly beef up the masthead and bow fitting which was showing signs of crevice corrosion. All my rigging and attachment points are now new. Paying someone else to fabricate the stuff would surely have been prettier but prohibitively expensive. There are also people who electropolish s.s. but I was not able to get a quote from anyone, I guess because it was not a big enough job.

Oh, and by the way, small chainsaw files are handy for tight spots. You'll also need some mill bastards for rounding edges.

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post #16 of 34 Old 02-07-2012
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I'm in the process of doing a similar job myself. What started as a "simple" job of fabricating new teak stand-off blocks for the pad eyes to which the boarding ladder attaches midship on both sides.

Once I got the old ones off, it was clear that new backing plates were gonna be a necessity, since the through bolts were not even close to being straight.

For the backing plates, I bought some 3/16" plate from McMaster-Carr.

Long story short, I bought some 1/8" stainless from McMaster-Carr. I marked the outline and cut it a little proud with a hacksaw, then to final size on a bench grinder, using it very gently at the slowest speed to keep the steel from heating up. I drilled the bolt holes with a 1/2 VSR drill, using first a 1/8" then 1/4" cobalt bits.

Polishing definitely was the most time consuming part of the project. Starting with 100 grit paper, and progressing through 150 emery cloth, then silicon carbide wet/dry in 220, 320, 400, 600, 800, 1000, 1500 and finally 2000. Followed that with some white rouge on a buffer wheel on the bench grinder. Final step was to hit it with some Prism Polish. They are now sporting a mirror finish.

Here's what I learned:

1. If you don't mind investing a pretty sizable amount of time, this can be done with hand tools alone. A bastard file probably wouldn't have been too much slower than the bench grinder for truing up the edges.

2. When you drill the plate, use cobalt bits. Drill at a very slow speed with a pretty good amount of force on the drill. If you aren't seeing a nice little corkscrew of material coming out of the new hole, all you are doing is heating up the metal -- which will harden it even further. As long as you go slow, cutting oil isn't necessary. After the first couple of holes you'll get a feel for the right speed/pressure combo.

3. Unless you are looking for a dead-flat surface, use a DA or RO sander for the initial sanding. After that, wet sand with a small sanding block.

Of course, if Garhauer can do this for you at a reasonable price then it'll probably be the best money you spend this week.
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post #17 of 34 Old 02-07-2012
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I second the Garhauer suggestion. I have always had good luck with these guys. But if you need something cut out of flat stock, find a machine shop that has a water jet for metal cutting. Supply them a drawing preferably in autocad, and they can cut parts very accurately with no tooling marks or heat distortion. You can even lay out holes to be cut instead of drilling them. Cool to watch too!

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post #18 of 34 Old 02-07-2012
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Quote:
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I'm in the process of doing a similar job myself. What started as a "simple" job of fabricating new teak stand-off blocks for the pad eyes to which the boarding ladder attaches midship on both sides.

Once I got the old ones off, it was clear that new backing plates were gonna be a necessity, since the through bolts were not even close to being straight.

For the backing plates, I bought some 3/16" plate from McMaster-Carr.

Long story short, I bought some 1/8" stainless from McMaster-Carr. I marked the outline and cut it a little proud with a hacksaw, then to final size on a bench grinder, using it very gently at the slowest speed to keep the steel from heating up. I drilled the bolt holes with a 1/2 VSR drill, using first a 1/8" then 1/4" cobalt bits.

Polishing definitely was the most time consuming part of the project. Starting with 100 grit paper, and progressing through 150 emery cloth, then silicon carbide wet/dry in 220, 320, 400, 600, 800, 1000, 1500 and finally 2000. Followed that with some white rouge on a buffer wheel on the bench grinder. Final step was to hit it with some Prism Polish. They are now sporting a mirror finish.

Here's what I learned:

1. If you don't mind investing a pretty sizable amount of time, this can be done with hand tools alone. A bastard file probably wouldn't have been too much slower than the bench grinder for truing up the edges.

2. When you drill the plate, use cobalt bits. Drill at a very slow speed with a pretty good amount of force on the drill. If you aren't seeing a nice little corkscrew of material coming out of the new hole, all you are doing is heating up the metal -- which will harden it even further. As long as you go slow, cutting oil isn't necessary. After the first couple of holes you'll get a feel for the right speed/pressure combo.

3. Unless you are looking for a dead-flat surface, use a DA or RO sander for the initial sanding. After that, wet sand with a small sanding block.

Of course, if Garhauer can do this for you at a reasonable price then it'll probably be the best money you spend this week.
+1 about drilling slowly with cobalt bits. My drill press, even on the slowest speed still tends to heat too much. I do use some cutting oil. The cobalt bits are also pretty easy to sharpen. Have also had some luck with good sharp titanium bits in a pinch. Don't worry about s.s. heating up when you work it. Heat treating does not harden s.s. Congratulations on a mirror finish! It's a LOT of work. Wish I had your patience but I usually give it the "good enough" classification below 1000 grit.

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post #19 of 34 Old 02-07-2012
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And you cant even remotely begin to cover the cost of drill bits and grinding wheels for what the water-jet place charges as its not like there super busy these days
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post #20 of 34 Old 02-07-2012
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Nice work Tom. I like your idea about plates under the stantion bases. May have to put that on the LONG to-do list. Wish I had thought of it when recoring the decks and all the hardware was off.

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