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Old 14-10-2013, 05:47   #1
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Grease in bolt threads

Hi and Thanks in advance,

I have hauled my boat and am doing some extensive maintenance. One of the things I have come across are bolts and fittings that are well rusted into place.

I have, for example, nuts that can't turn off their bolts because the threads are rusted badly; bolts (that compress my gland packing) so badly rusted in place that the snap instead of coming free; etc etc.

I also had a prop-shaft coupling that had rusted (a bit) onto the shaft and was v.diff to remove. In addition I have a rudder heel fitting with lots of large bolts that, although it wasn't a problem to remove, I would like to protect for the future.

After the difficulties in getting these apart I want to avoid that kind of rusting in future. If my budget was better then perhaps I could replace with better metals or something; but alas my budget isn't better.

So I am interested in what experience people have with greasing threads (perhaps copper grease?) before assembly. To me I can see the great idea of rust prevention and easy disassembly, but the fear that my stuffing box will undo its self and fly apart halfway to France because I greased the bolt threads and the nuts simply undo themselves.

I am thinking of areas like the threads/bolts that compact my stuffing box, my prop-shaft couplings, the bolts that hold my rudder-heel fitting to the keel. So a mix of damp moving parts and wet static parts.

Thanks for any help.

Duncan
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Old 14-10-2013, 06:36   #2
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Re: Grease in bolt threads

I think the usual standard for bolts used on yachts is Grade 316 Stainless Steel.
If you look around, these can be sourced fairly cheap (avoid yacht chandlers).
Rather than use grease, and anti galling compound may be a better means of protecting threads.
If you are worried about nuts working loose, use nylocs or a spring washer.
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Old 14-10-2013, 06:41   #3
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Re: Grease in bolt threads

I grease most anything. Lithium, polymer, lanocote, tefgel ... You can use spring washers if you fear things may come undone.

Loctite will stop things coming undone, if you prefer.

b.
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Old 14-10-2013, 06:44   #4
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Re: Grease in bolt threads

I use lanolin a lot. I even put it on the shackle to my anchor. Still holds tight and can be removed years later.
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Old 14-10-2013, 07:34   #5
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Re: Grease in bolt threads

The fastener I use where high-strength is required is the grade 8 ultra corrosion resistant (armor coat) fastener. They don't rust and they are very strong.

The stainless fasteners are not rated for strength.
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Old 14-10-2013, 07:52   #6
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Re: Grease in bolt threads

Quote:
Originally Posted by nigel1 View Post
If you are worried about nuts working loose, use nylocs or a spring washer.
Nylocs work well, but 1) they should be used only once; and 2) large stainless nylocs are somewhat more susceptible to galling than normal nuts.

Spring or split washers don't really work any better than plain flat washers once they are torqued flat. A chemical locking compound like Locktite is more effective. It can also help prevent corrosion and galling.
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Old 14-10-2013, 08:47   #7
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Re: Grease in bolt threads

Thanks everyone for the replies. i feel more comfortable using grease or oil. But perhaps the best way to go would be a locking compound as it would inhibit corrosion/galling and help keep everything together.

Thanks again.

Duncan
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Old 14-10-2013, 08:57   #8
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Re: Grease in bolt threads

Quote:
Originally Posted by DuncanC View Post
Thanks everyone for the replies. i feel more comfortable using grease or oil. But perhaps the best way to go would be a locking compound as it would inhibit corrosion/galling and help keep everything together.

Thanks again.

Duncan
Lanocote is grease, just one that that works well in this application.

John
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Old 14-10-2013, 09:40   #9
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Re: Grease in bolt threads

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Originally Posted by Ziggy View Post
Nylocs work well, but 1) they should be used only once; and 2) large stainless nylocs are somewhat more susceptible to galling than normal nuts.

Spring or split washers don't really work any better than plain flat washers once they are torqued flat. A chemical locking compound like Locktite is more effective. It can also help prevent corrosion and galling.
I think you can reuse the Nylok nuts until you see the plastic starting to come out the end ,I have also heated the plastic and pushed it back into the nut,would not do this on an airplane but i think its ok in most other places that are not going to be a high risk...I recycle most everything,some things are better off being replaced if critical..finger nail polish works well for thread lock and coating if not in a high heat app..
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Old 14-10-2013, 09:57   #10
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Re: Grease in bolt threads

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I think you can reuse the Nylok nuts until you see the plastic starting to come out the end ,I have also heated the plastic and pushed it back into the nut,would not do this on an airplane but i think its ok in most other places that are not going to be a high risk...I recycle most everything,some things are better off being replaced if critical..finger nail polish works well for thread lock and coating if not in a high heat app..
Actually, I reuse nylocs too, but not in any safety critical applications. If you intend to reuse them, you need to be careful not to exceed the torque limit. For most people, it's probably simpler to just replace them.
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Old 14-10-2013, 10:46   #11
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Re: Grease in bolt threads

I reused metric nyloks on the mounting bolts for my self steering vane. One of the nuts on the two bolts that hold the vane in place fell off. Nearly cost me the rig and forced a turn back and 180 mile motor to repair the transom. If it had happened much later would have been a long sleepless solo sail to Hawaii. Reused the bolts because I couldn't find a source for the metric SS nuts. Know about McMaster Carr now.

Lanolin is a great corrosion protectant but not a good lubricant. Water proof axle grease would probably be better for threads. LocTite works because it seals the threads so water doesn't get in. Antisieze compound should be used on SS bolts with high torque loads to prevent galling the threads. It seems to be good at preventing thread corrosion though don't know its long term resistance to water penetration.
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Old 14-10-2013, 10:59   #12
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Re: Grease in bolt threads

Boeshields T-9, good enough for Boeing aircraft. I have used it for 16 years on my boat. Dismantled my laptop, radar, autopilot and coated the electronics, my throttle/shift linkage, my fuel tank, my engine, wiring harness and everything else.. and have never seen a spot of corrosion.
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Old 14-10-2013, 11:01   #13
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Re: Grease in bolt threads

Lanolin or grease is great. Very often over looked and should be put on those things. Also, for protecting exposed parts of the fasteners, CRC 5-56 is great. It's pretty much the same as Cosmolene used to protect military arts in storage etc. (it's getting a little hard to find for some reason)
Also, DO NOT use nylok nuts on a engine shaft coupling. During a haul out and "trying to make everything perfect" episode, I removed, cleaned up and painted the coupling. I put new bolts and decided that nyloks would be good there. The coupling came loose in less than a month! What a rattle, damaged some of the coupling holes too.
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Old 14-10-2013, 11:08   #14
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Re: Grease in bolt threads

Anti Seize and Never Seize are two products that come to mind.
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Old 14-10-2013, 11:47   #15
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Re: Grease in bolt threads

Obviously, those bolts that snapped off need replacing. And I have to admit, I feel a little weird about using anti-seize on those ones, but honestly, you'll want to use something, and we have NOT found that Loc-tite functions well as an anti-rust device. Probably, the snapping is due to weakening of the bolt due to oxygen deprivation corrosion, and we've lost both bolts and nuts from that cause. And, IMO, not a good place to use Ny-Loks.

What we use now is anhydrous lanolin, and have not had the nuts try to un-do. Still, if I were in your shoes, I would check the buggers, possibly before and after each run, till I taught myself to trust them. They gotta prove themselves trustworthy.

Roverhi, sorry to disagree with you on this one, but that old pound tub of lanolin has been wonderful over the years, and we wouldn't be without it. Even use it in some places where there are dissimilar metals, and so far, so good. And this on a boat that thinks it's fun to un-do stuff like gooseneck fittings, main boom and boom vang, and the sistering plate where the vang attachment exits the boom. Incidentally, we used to use the silver anti-seize exclusively.
YMMV
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