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Old 26-01-2009, 12:02   #1
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Anyone fabricate their own chainplates?

Along with damage to my bowsprit, pulpits, stanchions, deck, gelcoat, mast and engine - hurricane Ike also bent or severely damaged every chainplate on the boat. I found that I can get enough 1/8 304 ss flat bar to replace all of them for about what most 'marine outfitters' are asking for a single chainplate (if not less). Has anyone fabricated their own chainplates? What special consideration needs to be taken when approaching such a project (ex. bending, drilling, polishing)?

Looking for any advise and/or guidance.
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Old 26-01-2009, 12:29   #2
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Drilling stainless is a royal pain. Wouldn't even want to think about cutting it to width. First, I'd get 316ss or, better yet, bronze. 316ss is way more corrosion resistant than 304 and won't bleed or suffer as much from crevice corrosion as 304. Bronze has none of the corrosion problems of SS but is way more expensive. The machining costs should be less for Bronze, however.

I'd look for stainless flat stock in the thickness and width that you need. You could cut the chainplates to length with a cutting wheel on a hand grinder then buff and polish as necessary. You'll need to either buy or borrow a drill press to drill the holes. Get Cobalt bits and drill really slowly with a constant high pressure feed. A machine shop with a mill is way more efficient at drilling the holes.

When I get around to replacing my chain plates, I'm going to find a source of the proper sized flat stock and then have a machine shop cut them to length, drill the holes, and bend them where necessary. It's way more efficient than doing it myself and should be way cheaper than buying them ready made.

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Old 26-01-2009, 14:36   #3
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Find a small local machine shop and have them fabricate them for you. Don't mention the word "Marine", just tell them it's some kind of project you are working on. Polish them yourself.
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Old 26-01-2009, 14:53   #4
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Find a small local machine shop and have them fabricate them for you.
You really need good stock to start with 316 SS is what to use. 304 is not acceptable yet it is a lot cheaper. The corrosion resistance is more important. If you can layout a pattern for cutting any decent machine shop can do this work. In the spectrum of machine work this isn't at all difficult compare to much of the precision work they regularly do. Most shops can sneak in a small job and it does not need to be a expensive job.

Given the pain it is getting the old ones out and having to reinstall new ones cheaping out on a little labor and material isn't that much. If the stock can be cut with a water saw you can reduce the polishing needed at the end. The holes come out square when done that way. Stainless is polished to reduce potential crevice corrosion. Any shop that works 316 will know what it takes. You really won't look forward to doing this job again so get it right and sleep better knowing.
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Old 26-01-2009, 15:53   #5
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Definately opt for 316. Most steel suppliers can shear the stainless to the width you need or a slow bandsaw (50 fpm) and a good nmetal cutting blade will make short work of it. Drilling it is'nt a problem if you have a slow drill press, a good bit, and a can of wd-40. You can even use holesaws on stainless if your turning them slow enough.

Small machine shops that will do small custom jobs can sometimes be difficult to find. If you're in the New England area there is a good one in the Wickford Ship Yard, Wickford R.I., and if you stop in to see Don, tell him hellow from his freind in Cinncinati.
Quidam (pronounced "key-DAHM"; IPA: /kiːˈdɑːm/) means "a certain one" -or- "a certain thing", "an anonymous passerby" in Classical Latin
One must be constantly on guard against advocates of the "Be reasonable and do it the hard and expensive way" school of thought.

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Old 26-01-2009, 16:00   #6
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>I found that I can get enough 1/8 304 ss flat bar to replace all of them for about what most 'marine outfitters' are asking for a single chainplate (if not less).<

I bought some 304 and 316 stainless flat stock last year to make some parts for the Catalina 27. Surprisingly, 316 was not much more expensive than the 304, and neither were very expensive considering the small amount of material needed.

The corrosion resistance of 304 vs 316 may only be important in a salt water environment, although for critical parts like chainplates I wouldn't scrimp. Also note that if the parts require welding--the chainplates on my 38 Irwin do--there is a special grade of 316 required (316L??).

Stainless is easy to drill if you have a drill press and use the right technique (lubricant, pressure, a sharp drill bit, and slow turn speed). Any steel is hard to drill without the right technique.

With patience you can rough cut the parts to size using a metal cutting bit and a hand jig saw. I used a metal cutting blade on my small bench mounted band saw, and it worked great. I tried the jig saw a little and saw that it could work, but was slower--buy extra blades

>Stainless is polished to reduce potential crevice corrosion. Any shop that works 316 will know what it takes.<

The polishing and passivating steps are critical if you are going to make SS parts that will last in a salt water environment. The steps are:

1) Rough cut part to shape and drill holes
2) Sand edges smooth using a belt or disk sander
3) Sand all surfaces smooth using a DA sander and progressively finer grits
4) Mechanical polish using Buffing wheel and buffing rouge
5) Passivate (using citric or nitric acid)
6) (Optional) Electropolish (using citric acid)

The passivation and electropolishing steps get rid of the last remaining bits of iron extending through the chromium dioxide passivation layer. With the iron gone, the part cannot rust unless the CRO2 layer is scratched.

Even a lot of "professionally" manufactured stainless steel parts are not well passivated and polished, and you can tell it by the way that they start to rust in the ocean environment.

Good luck with it,

Don W.
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Old 26-01-2009, 16:08   #7
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The attachment bolts are probebly carriage bolts so the holes through the chainplates will have to square. A shop with a water jet is the way to go, and they can do all the other cutting, too. Leaves very nice edges and causes no metal discoloration from the heat generated by a friction wheel for example.
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Old 26-01-2009, 16:25   #8
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I found a machine shop which cut my chain plates from 1/2"X 3" 316ss bar stock using a cnc water-jet. Quick and easy. Bring a drawing. Dimentions are entered on a computer and the bar stock loaded in the machine. It will
cut using a water-jet and abrasive. The process generates no heat. Heat will cause stress in stainless which will lead to cracks.They also did the bends necessary to match the originals. The work was done while I waited and the cost was very reasonable.
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Old 26-01-2009, 16:27   #9
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Yes, I have. Here's a good place to get your 316: Speedy Metals Online Industrial Metal Supply
You wont need to cut it for width, they have every size you will need. Call them, and see if they will cut precise length...I didn't do this and I should have. Shape corners and ends with a table belt/disk sander, BUT DON'T OVERHEAT THE METAL! (unless you want it to rust) To drill this GOD AWFUL stuff, use a constant flow of condensed milk. (nice, nutty smell) If you cant find a drill press and a way to constantly flow coolant... DON'T BOTHER WITH THIS PROJECT! Slower drill speed is best. You can polish with SS rouge and a sewn buffing wheel in a hand drill mandrel. Passivate as above. This aint fun work, trust me!

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Old 26-01-2009, 16:56   #10
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I made new chainplates using 316ss. I had to oversize a bit as the exact dimension stock was not available. I had access to a metal worker machine for cutting to length, used a sander to round the ends and had a machine shop drill all the holes ( they charged about what I figured it was going to cost for the bits). Having polished stanchion bases that I made, I opted to have a polishing shop do the mirror finish polishing and I'm glad I did (to get a good mirror finish takes a LOT of time). There is nothing very easy about working with SS. I figure that I saved about 50% off a quote I was given to have them made, if I don't count my time.
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Old 27-01-2009, 15:38   #11
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Without commenting on what others are posting above here's my normal dissertation on chainplates:

Material Choice:
Type 316 is an ideal choice and for thru-deck type chainplates should be the only one seriously considered but it is not the only choice. Type 304 is certainly acceptable for external chainplates that have been well polished and are well maintained. Aluminum of sufficient grade and thickness can also be used and in some production cases is used to great effect. Refer to "Skene's Elements of Yacht Design" for scantlings.

If you are making simple strap type chainplates purchase bar stock the width you need. Do not cut or drill your stock until 95% of your polishing work is done (see below). Chop saws with abrasive bits make the quickest work with bandsaws being a close second if you have access to a bandsaw with a deep enough throat. You can (regardless of what you may hear) cut stainless with a hacksaw. Use the best quality blade you can find and mount it to a high tension saw. Lubricate the cut frequently and you will not have any issues.

There's a world of misinformation out there on stainless drilling. It's an easy material to deal with if you use the correct technique. Best choice is a drill press (well, aside from a mill) set to it's slowest setting but a good hand drill will be able to do it. I've drilled a 3/8" hole through 1/4" stock with a black and decker hand drill from walmart. The key is a variable speed drill operated as slow as possible. One you are set to drill get on it and commit. Do not stop to check your progress. If possible, use a steady stream of actual cutting fluid but in a pinch any cooling, lubricating fluid will work. If you burn up your drill bit you are generally stuck with a hardened hole you'll never get through so you generally get one chance. Do not rush the job and you'll have no problems. Also, while a high quality bit is nice it is by no means required.
DO NOT use square holes. This applies to chainplates, holes in masts, etc. Corners are a stress nightmare. Countersunk fasteners in external chainplates aren't great either.

Mounted belt sanders and hand angle grinders are your friends. I've had much more luck with sanding discs on a grinder than I've had with a stone. I wouldn't necessarily duplicate your old plates just because that was the original equipment. Just because it was original doesn't mean it was correct. Try Skene's again to get general dimensions for the top end of the chainplates. I believe there is also a copy of the Skene's table in Brion Toss's "Riggers Apprentice"

Cold bending should be able to take care of most of your needs. Ideally a press and a jig you make up for the task is the way to go but it is possible to get acceptable results with a vise and rubber mallet. Any bends need to be made before you drill.

Mill finish bar stock is heavily pitted from the rollers the sheet stock is pressed through. It's also frequently slightly cupped. Step one is getting down below these imperfections. Using drywall screws edge-screw your bar stock to a work table.
Now hit with a belt sander armed with 60 or 80 grit. This is the singlemost time consuming and mind-numbingly boring part of the whole job. Keep the belt sander orientated the same way and work the metal over slowly and consistently until you've sanded away the last of the pits.
Cool the metal with water frequently or you'll burn through the sandpaper and scorch your table. A belt sander really is the only tool aggressive enough to do the trick but it's easy to screw up. Keep it flat or you'll gouge the metal.
After you get a good consistent finish with the coarse paper drop to 120 grit and sand again until you get an even dull look. After the 120 grit it's time to switch to a buffer/sander with 220 grit also worked with a flat tool (do not pick it up to edge sand no matter how strong the urge). 400 grit on that same sander is the last step before the buffing wheel. It's at this stage that you are ready to cut,bend,and drill your stock.
Chances are you'll need to touch up areas after you drill. The little spirals of metal coming out of the holes tend to scratch up the area around your holes. Hit these with the buffer/sander again with the 400 grit if they are light enough or the 220 followed by the 400 if they are deeper.
Buff with white rouge on a bench grinder or angle grinder fitted with a buffing wheel. Mount and enjoy. Seal with 101 or other polysufide based sealant NOT 5200.
All of this represents a good saturday's worth of work and is certainly within the realm of do-it-yourself. It's not unusual to the able to buy the stock AND the tools and do it yourself for less than buying a set of chainplates and then you have the basic toolset for doing 99% of the custom metalwork on your boat (linkplates, tangs, backing plates, etc.) and a good bit of experience to boot.
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Old 27-01-2009, 16:51   #12
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Boats is dead on.....

I made my own chain-plates on a couple of boats. In fact, I wouldn't let anyone else make them.

The one thing that I added was that I sanded mine down to 220G then had them electro-polished. I also had them x-rayed for cracks. I rejected a lot of material.

I will repeat what others have said. S/S is easy to work with if you follow Boat's instructions. Using the correct cutting fluid is critical. Also (as Boats said) once you start cutting, don't stop. If you do, the metal cools and hardens. S/S is a soft material and cuts easily. As you drill it gets very hot and if you let it cool, you'll have a hell of a time getting started again and may ruin a drill bit or two.
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Old 27-01-2009, 18:14   #13
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And, as an alternative opinion, carbon fiber chain plates seem to me to be the ideal for through deck chain plates.
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Old 15-03-2009, 10:19   #14
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I made mine out of 10x50 mild steel which I then had galvanised, for my wooden 60s sloop. They seem to work fine.

Electrolytically, galvanised and stainless are not that far apart for it to be a problem I have been told and no problems after 2 years.

Certainly a biggish slowrunning bench drill press is a real boon for this type of job.
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Old 15-03-2009, 11:13   #15
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I have always made my own but I was a machinist/toolmaker at the time. Forget 1/8"...use 1/4". Buy flat bar the width you need, so cutting to length with a chop saw is all you need to do. The technique to drilling stainless is a steady solid drilling base and lower drilling speeds with new drills and sulfur base cutting oil. Do it right! No hand drills with motor oil. You would be wasting your time and posting in forums how difficult stainless is to drill. Use a drill press at about 300 rpm. Start with a center-drill. These are had at a machine shop supply house. It's unlikely the center-drill will drill all the way through, so finish it with a 1/8" drill through, all the time brushing on plenty of oil. Then use your finish size drill. I find I have the best luck using what is called a stub drill. They are short and the grind on them is better for stainless. Use a chamfer tool to pretty the entries of the holes. Power sand a finish on the stainless and if you can afford it, get them electro-polished.
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