Chain Plate Life Span

[Jon Hacking]

Originally Posted by stevensuf

ok some pics attached ...

Those turnbuckles are fairly common, but I have a problem with them. The strap-toggle goes around a big slug, & the stud from the turnbuckle threads into that slug. The stud is welded to the slug on the bottom, but in '83 we broke one of those turnbuckles on our headstay beating into Virgin Gorda. The stud broke about 1 turn down into the slug, an area that's impossible to monitor. OK, the turnbuckle could have been old (we'd only owned the boat for a couple of years then) but I still don't like not being able to inspect for trouble. We were very lucky not to lose the stick.

[Bridger]

I would rather drill, shape and polish myself.
Sounds like the key to drilling & grinding is to not let the 316 get to hot, is that right? Will that stop work hardening, If I keep plenty of water on it? What is the best way to polish?

[Erik de Jong]

When designed properly and made of low carbon stainless(316L for example) than your chainplates out-live you easily. Proper design means that the stress levels in a worst case scenario are below 40% of the yield strength of the material. If that is the case, fatigue is not a risk, if low carbon stainless is used, corrosion due to low oxigen is not a risk anymore.

Problem is that most chainplates are made of 316 and 304 ss and than glued airtight to another structure. If glued and bolted to an "aired" structure, they will live for life as well. The difference beteen 304, 316 and 316L cannot be seen with the bare eye, it needs to go to a lab. When changing your chainplates, consider upgrading to the low carbon steel or make the construction such that the chainplate is in conenction with air as much as possible.

[sabray]

I used a belt sander with 120 grit then a sisal wheel on a bench grinder/polisher used with with black emory compound. Then finish with green S.S. compound ans spiral sewn wheel.
You might check this place out. Plating Kits Electroplating Kits Aluminum Anodizing Kits Powder Coating Systems Metal Polishing And Buffing Supplies - Caswell Inc
+1 for 316L

[Marner]

It's what you can't see that you need to worry about. Pitting corrosion occurs in stainless steel in the absence of oxygen if in contact with water. The photo shows corrosion on chainplates removed after some 15 years of service. The corrosion only occured where the chainplate passed through the deck. Above and below they looked fine.



I had installed these without sufficient clearance to allow a good seal with caulking. Sealing is everything. They were reinstalled with a larger clearance and lots of sealant! I considered the pitting to be minor as these are 1" x 3/8" chainplates and the rigging wire is only 1/4".

On the subject of polishing: It's Electro-Polishing that is required to remove the impurities from the surface. This is something that requires special equipment.

Marner
__________________________________
http://cruising-cape-breton.info

[Cheechako]

For drilling, you need to get the feed rate and speed right. Then the drill will just cut it's way through making nice spiral chips. Too fast it will destroy the bit immediately and make the hole almost impossible to drill with a fresh one. Use a cutting fluid and go slow to start using a drill press. At the right feed rate, your drill will be just almost pulling it's way through the metal. You could eat up $25 in supplies easy and a small shop might drill your centerpunched holes for maybe $50... hard to say I guess.

[delmarrey]

Here's a good thread on drilling SS.>> http://www.cruisersforum.com/forums/...teel-9238.html

[sabray]

More then one way as always. once years ago I used cobalt tipped bits was very expensive. Someone here suggested using regular steel bits and water. So I tried it. Damn if I didnt do 9 chain plates 3/8" 316L with 7 1/2" holes in each used 2 bits. I sharpened them after finishing a chainplate. still have those 2 bits. Proper slow speed and lots of water cooling . Un believable how easy it was. No oily mess very little expense. knowing how to sharpen a bit helps but that is not hard.