# Keel bolt torque values ????



## anerussis (Dec 26, 2011)

After reading some postings suggesting that the keel bolts should occasionally be re-torqued I decided to do just that on my recently acquired 1977 C&C 26.

There are several 1/2" nuts and 1- 1/2" nuts on the keel bolts. I used my breaker bar on the 1/2" nut expecting a battle but was able to quite easily tighten it at least 1/2 a turn. I did not attempt to tighten the rest fearing that I may cause more damage then good and possibly break the seals causing leaks.
Does anyone know the torque values for these 1/2" and 1 1/2" nuts or does one just tighten by feel which would of-course very by the size and strength of the individual.


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## RobGallagher (Aug 22, 2001)

anerussis said:


> After reading some postings suggesting that the keel bolts should occasionally be re-torqued I decided to do just that on my recently acquired 1977 C&C 26.
> 
> There are several 1/2" bolts and 1 1/2" keel bolts. I used my breaker bar on the 1/2" bolt expecting a battle but was able to quite easily tighten it at least 1/2 a turn. I did not attempt to tighten the rest fearing that I may cause more damage then good and possibly break the seals causing leaks.
> Does anyone know the torque values for these 1/2" and 1 1/2" bolts or does one just tighten by feel which would of-course very by the size and strength of the individual.


CNCphotoalbum.com has torque values listed by bolt size.


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## anerussis (Dec 26, 2011)

RobGallagher said:


> CNCphotoalbum.com has torque values listed by bolt size.


Yes I saw that but it does not list 1-1/2 " bolts --- It show 80 lbs for 1/2" and 450 lbs for 1 1/4 bolts - but would that apply to all keel boats large and small - 18 ft to 40 ft + boats?

Feel a bit dumb but just realized the nut size is 1- 1/2" and not the bolt size. I measured the nut in order to buy the socket - bought a 38mm socket which fits fine. The 1 1/2" nut / 1"bolt size to be torqued to 350 lbs -- and the 1/2" nut 5/16 bolt to 80 lbs right?


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## Sabreman (Sep 23, 2006)

One of the routine maintenance chores that I do in spring is to tighten keel bolts. I use a 3/4" socket wrench with a 1 1/2" socket and a pipe extender. Then I torque as much as I can. It's a keel. They're big honkin' bolts. As much torque as I can apply is what I want. :laugher

With that said, Sabre recommends 90 ft lbs torque.


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## anerussis (Dec 26, 2011)

Sabreman said:


> One of the routine maintenance chores that I do in spring is to tighten keel bolts. I use a 3/4" socket wrench with a 1 1/2" socket and a pipe extender. Then I torque as much as I can. It's a keel. They're big honkin' bolts. As much torque as I can apply is what I want. :laugher
> 
> With that said, Sabre recommends 90 ft lbs torque.


According to the chart 1 1/2" socket is for a 1" bolt - torque to 350 ft lbs - if you tighten past that would there not be a danger of pulling the bolts from the keel or crushing the fiberglass?


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## RobGallagher (Aug 22, 2001)

I can only tell you that I rented a large (monster) torque wrench and sockets from a tool rental joint and followed the chart for 1" bolt w/ 1.5" nut. There where no disasters that followed. If memory serves me...


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## Sabreman (Sep 23, 2006)

Sabre recommends 90 ft lbs for a 6,800# keel. I'm pretty sure that it's a 1 1/2" nut on the bolt, but either way, I tighten as much as I can by hand while the boat is blocked. Close enough. On both my Sabres, I was able to get about 1/8 a turn on some of the bolts the first time that I did it. Thereafter, they've never budged.

If the bolt breaks from hand tightening using a standard socket wrench, then the bolt was going to let go anyway. The keel area is one of the most heavily reinforced areas on all boats. If the fiberglass crushed on a hand tighten, then the keel bed was degraded anyway and it's a blessing that you found out sooner rather than later.


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## SloopJonB (Jun 6, 2011)

Sabreman said:


> One of the routine maintenance chores that I do in spring is to tighten keel bolts. I use a 3/4" socket wrench with a 1 1/2" socket and a pipe extender. Then I torque as much as I can. It's a keel. They're big honkin' bolts. As much torque as I can apply is what I want. :laugher
> 
> With that said, Sabre recommends 90 ft lbs torque.


"Give me a lever and a place to stand and I will move the world".

There is a reason torque wrenches were invented - you can exert a HUGE amount of force when you put a pipe extension on a wrench, enough to shear the threads or snap the stud. Stainless steel is also easily galled when too much torque is applied. I can quite easily apply over 100 Ft. Lbs with one hand and a 1/2" drive torque wrench.

Use a torque wrench and tighten the nuts to the torque specified for that size stud. Even a cheap torque wrench is going to be a LOT more accurate than "a piece of pipe and as hard as I can".


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## Sabreman (Sep 23, 2006)

SloopJon- you are correct and I don't do that any longer, just tightening by hand with a regular socket wrench. I should have been more clear in my explanation. Thanks for pointing that out. I should buy a torque wrench, and this may be my impetus.


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## jgeissinger (Feb 25, 2002)

I am glad SloopJonB made his response. Re-torqueing keel bolts (actually you are torqueing the nuts, not bolts) is a subject that comes up periodically, and almost always with bad advice. He is absolutely correct in that it is not that hard to break perfectly good bolts by over tightening. It should also be noted that torque values are given for clean and lubricated fasteners, which keel bolts and nuts usually are not. Just my two cents.


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## msmith10 (Feb 28, 2009)

If you have 1-1/2" keel nuts, you should have 1" keel bolts. In that case the torque setting is 350 ft lb. You can also get a tool called a torque multiplier to attach to your torque wrench since most torque wrenches won't go up that high. I bought one years ago for only this job. You'll probably also need a deep-well socket. You'll need 3/4" drive to get this kind of torque.
I'd also recommend watching your keel-hull joint. The C&C smile (separation of that joint) is common as the keel nuts loosen up with time, and the fix most guys do is just to fill the joint with caulking or epoxy, neither of which will last long.
If you have some separation, or it's been filled, I'd recommend cleaning out the joint before you tighten the nuts, then torque the nuts, then fill the seam if there's any left. Also be sure to caulk around the bolts before tightening the nuts-- I remove the nuts and washers, one at a time, clean out any bad stuff, recaulk, make sure the washer or backing plate is in good shape, then replace the nut and tighten, but not to full torque setting. After doing this with all the nuts, I go back and retorque part way on each nut at a time, like you're doing a cylinder head, until all nuts are at desired torque.
You should only have to do this every several years.


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## Sabreman (Sep 23, 2006)

> I remove the nuts and washers, one at a time, clean out any bad stuff, recaulk, make sure the washer or backing plate is in good shape, then replace the nut and tighten, but not to full torque setting. After doing this with all the nuts, I go back and retorque part way on each nut at a time, like you're doing a cylinder head, until all nuts are at desired torque.
> You should only have to do this every several years.


I've not done this on either of my keel boats. I'll have to think about it. I've only ever tightened the bolts using the logic that if the keel joint isn't separating and if it isn't leaking, why open a can of worms? On the other hand, my logic is flawed on several levels because when I've opened seemingly solid covers, dry walls, tiling, etc, etc, I've found stuff in desperate need of repair. Thanks for raising an important consideration.


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## msmith10 (Feb 28, 2009)

On a 35 year-old boat, everything must be considered suspect.


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## anerussis (Dec 26, 2011)

Sabreman said:


> One of the routine maintenance chores that I do in spring is to tighten keel bolts. I use a 3/4" socket wrench with a 1 1/2" socket and a pipe extender. Then I torque as much as I can. It's a keel. They're big honkin' bolts. As much torque as I can apply is what I want. :laugher
> 
> With that said, Sabre recommends 90 ft lbs torque.


Well I did just that - bought a 1 1/2" socket and a 3' breaker bar - was told that no way would I be able to torque past and most likely not even to the 350 ft. lbs spec. of a 1" bolt. My keel has three (3)1" bolts with 1 1/2" nuts - was able to turn each one an additional 1/2 to 3/4 turns. The keel also has two (2) bolts with 1/2" nuts the specs suggest 90 ft. lbs of torque - I have a cheapy torque wrench and to my surprise the nuts of these bolts turned several times before reaching 90 ft. lbs. *NOW I'm a bit concerned because just because the specs for these bolts state that they may be torqued to specified values doesn't necessarily mean that for keel applications they should be maxed out - or does it*?


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## midnightsailor (May 23, 2003)

FWIW: I just came across the following keel bolt torque specifications on another Sailboat Forum. This was taken it said from DIY magazine 2004-3 :
KEEL BOLT TORQUE SPECS :

Bolt-Diameter.........Foot-Pounds............Nut-Size
0.5".......................80........................0.75" 
0.75"....................250.......................1.125"
1.0".....................350........................1.50"
1.25"....................450.......................1.875"

Rick


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## SloopJonB (Jun 6, 2011)

anerussis said:


> Well I did just that - bought a 1 1/2" socket and a 3' breaker bar - was told that no way would I be able to torque past and most likely not even to the 350 ft. lbs spec. of a 1" bolt. My keel has three (3)1" bolts with 1 1/2" nuts - was able to turn each one an additional 1/2 to 3/4 turns. The keel also has two (2) bolts with 1/2" nuts the specs suggest 90 ft. lbs of torque - I have a cheapy torque wrench and to my surprise the nuts of these bolts turned several times before reaching 90 ft. lbs. *NOW I'm a bit concerned because just because the specs for these bolts state that they may be torqued to specified values doesn't necessarily mean that for keel applications they should be maxed out - or does it*?


Yes. Torque specs are merely a best effort substitute for the ideal method of tightening a bolt/nut, which is to measure the *stretch* of the bolt. Since measuring bolt stretch is difficult to impossible in many cases, torque values which equate closely are used instead.


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## anerussis (Dec 26, 2011)

midnightsailor said:


> FWIW:
> KEEL BOLT TORQUE SPECS :
> 
> Bolt-Diameter.........Foot-Pounds............Nut-Size
> ...


Yes the same table can be found on the C&C do it yourself web pages. However as I stated earlier I used a 3' breaker bar and torqued as much as I could. I did go to a rental place and they showed me a MONSTER of a torque wrench that could do 350 to 500 Ft Llbs. It's handle was longer then 4' and it was also quite bulky and heavy.There was no way that I could get enough clearance to work this thing in my 26' C&C. Was advised that if I used a 3' breaker bar it would be near impossible to get close to 350 ft lbs and therefore no worry on damaging the bolts. *Has anyone actually torqued their 1" keel bolts to 350 ft lbs ? * What difference would it make if the bolts were torqued less to between 150 & 200 ft lb??? .I am still concerned that a high torque (350 ft lbs) on an older boat may result in damage such as crushing the fiberglass and worse.


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## anerussis (Dec 26, 2011)

SloopJonB said:


> Yes. Torque specs are merely a best effort substitute for the ideal method of tightening a bolt/nut, which is to measure the *stretch* of the bolt. Since measuring bolt stretch is difficult to impossible in many cases, torque values which equate closely are used instead.


Yes I am aware of this having been involved in studies on the elongation of rebar and bolts used in the containment areas of nuclear power stations. However we are talking about sailboat keels of say 2000 - 2500 lbs the weight of which is distributed over several bolts. The torque values most likely should be calculated per application and consider other factors such as crushing of fiberglass and other materials used. I am not questioning the tables showing the max torque values of bolts but would like to know the torque numbers the actual boat designers and builders suggest.


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## unhappysailor (Mar 18, 2015)

Hi there, I have a Carter 33 and a small crack has appeared between the keel and the hull from the front going back 12 inches. I'm going to check the keel bolts but I don't know the torque values. Any idea where I would find them and is there anything else I need to know? Many thanks


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## SloopJonB (Jun 6, 2011)

unhappysailor said:


> Hi there, I have a Carter 33 and a small crack has appeared between the keel and the hull from the front going back 12 inches. I'm going to check the keel bolts but I don't know the torque values. Any idea where I would find them and is there anything else I need to know? Many thanks


Look here;

Steel Bolt Torque Specifications Table - Engineer's Handbook

Torque values depend on the fastener material & size, not so much the job they are doing.


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## RichH (Jul 10, 2000)

Use this table and use the 18-8 Stainless for the torque values: Bolt Torques - Stainless Steel, Brass Aluminum Bolts - Engineer's Handbook
For suspected 'weakened' fastners due to corrosion, etc., I personally would use only ~80% of max. of those 'table values' ...... and trust/depend on the inherent safety factor that the OEM designer '_probably_' applied.

Do it this way: apply 50% torque value, unload and then repeat to -60%, unload and repeat to ~70% etc. etc. etc. ... and done 'slowly'; dont 'jerk it' when torquing. Obviously if you have bolt failure at 50% etc. , then there's no use in 'busting them all'.

Also do websearch for: 'repetitive torquing' .... and also the differences between and "dry" vs. "lubricated torquing"


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## casey1999 (Oct 18, 2010)

Interesting Article:
http://www.j24class.org/news/keel-bolt-maintenance-bulletin/

Keel Bolt Maintenance BulletinJune 09, 2011
There aren't many maintenance areas that are more important, or more often overlooked than keel bolts. This is true for every boat, but particularly so for J/22s, J/24s and J/80s, all of which routinely hoist the boats in and out of the water using the bolts.

Failure of any keel bolt is bad, but most bolts are part of a massively redundant system, where the failure of any one bolt is rarely immediately catastrophic. For boats that are hoisted, the failure of a bolt holding the lifting gear can be catastrophic and has the potential to lead to the loss of the boat, or much, much worse.

While this article is being distributed to USWatercraft and J/Boats customers, it applies to virtually all production boats, regardless of builder or brand. If they use Stainless Steel keelboats and most of them do, it applies. Feel free to pass it along to your friends and fellow boat owners. It's pretty important.

Since they live in the bilge, keel bolts can fall into the category of "out of sight, out of mind". It is because they live in the bilge that they need routine care and attention.

J/22 keels are made using 316 Stainless Steel threaded rod, which is cast into the lead. The nuts, washers and lifting bar are made using 304 Stainless and are then electro polished. This has been the industry standard for many years, and has provided many years of service life.

Stainless Steel is corrosion resistant, not corrosion proof

The basic resistance of stainless steel occurs because of its ability to form a protective coating on the metal surface. This coating is a "passive" film, which resists further "oxidation" or rusting. The formation of this film is instantaneous in an oxidizing atmosphere such as air, water, or other fluids that contain oxygen. Once the layer has formed, we say that the metal has become "passivated" and the oxidation or "rusting" rate will slow down to less than 0.002″ per year (0,05 mm. per year).

Unlike aluminum or silver this passive film is invisible in stainless steel. It's created when oxygen combines with the chrome in the stainless to form chrome oxide, which is more commonly called "ceramic". This protective oxide or ceramic coating is common to most corrosion resistant materials. Unfortunately Halogen salts, especially chlorides easily penetrate this passive film and will allow corrosive attack to occur.

CONCENTRATED CELL OR CREVICE CORROSION

This corrosion is common between nut and bolt surfaces. Salt water applications are a severe problem because of the salt water's low PH and its high chloride content. Here is the mechanism:

• Chlorides pit the passivated stainless steel surface.

• The low PH salt water attacks the active layer that is exposed.

• The absence of oxygen inhibits the re-forming of the passive layer.

These three factors work together in a vicious cycle, repeatedly attacking the same small area. If the metal is under tensile stress- like from an over torqued keel bolt nut, the pit formed can transform itself into a crack. When a crack forms the process repeats and accelerates as the surface area of the 'active' layer is now much larger.

Prevention is the best cure

The best way to prevent corrosion is to keep salt away from your bolts. The best way to do that is to keep your bilge clean and dry. We've designed our interiors to be easily washed down. Take advantage of this. At the end of the day, when you hose off your deck hardware, stick the hose down the companionway and blast out the bilge and bolts. Pump and sponge dry and leave the floorboard off when you leave. Not only will this protect your keel bolts from corrosion, it will prevent mildew and keep your interior looking and smelling fresh.

Important note! Avoid using any cleaning products containing chlorine. Chlorides are just what we are avoiding. Read the label. Clorox, Comet, and Fantastic are all products that while good for most stuff are bad for this application. Check the label.

Annual Maintenance

Checking your keel bolts should be part of your annual maintenance plan. Working one bolt at a time, remove the nut and washer and clean the threads with a small nylon or brass brush or scotch brite. Do not use a steel wire brush, as this can lead to other corrosion issues not covered here! Check for signs of rust. If everything looks good, use a generous coating of anti-galling compound and re-torque the nut. Most J/22 keel bolts are 5/8

Keel Bolt Torque Table

Bolt Diameter Torque Ft/Lb 
1/2″ 19.2 
5/8″ 48.7 
3/4″ 95.9 
7/8″ 140.1

This Table is derived from information in Table A7 from ISO/DIS 12215-9.2. These values are for well greased threads. Friction in the screw and under the bolt head makes up approximately 90% of the tightening torque and approximately 10% contributes to prestressing of the bolt. The user is cautioned to use good judgment in applying these values.

Tip- If you can pull in your mainsheet, you probably don't need a big breaker bar to torque your nuts. Over-torqueing is extremely bad. Particularly on the bolts holding your lifting rig, under-torqueing is equally bad. If the nut is loose enough to allow movement in the bar, the bolt can be loaded unequally, leading to tension stress on one side of the bolt.

While you are there

Since you are spending some time with your bilge anyway, this is a good time to give the rest of your lifting gear a good look over. Check your sling for any signs of wear; fraying, cuts, abrasions and the like. Your sling should look essentially new.

If you use a shackle in your system, check it too. If it is bent, rusted or shows signs of wear, just replace it. A new sling costs around 50 bucks and a shackle around 9 bucks. It is the cheapest peace of mind available.

If you think you find a problem

If you find or suspect you have problems beyond a good cleanup you should contact a marine surveyor who can inspect and report findings. Your surveyor will have the specialized knowledge and tools to give you an informed recommendation.


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## albrazzi (Oct 15, 2014)

casey1999 said:


> Interesting Article:
> http://www.j24class.org/news/keel-bolt-maintenance-bulletin/
> 
> Keel Bolt Maintenance BulletinJune 09, 2011
> ...


Casey; how do you feel about washers spanning two bolts in a keel mounting system. Specifically my cs30 has three sets of (2) keel bolts and they each share a plate not a regular washer but a backing plate connecting the two nuts. There is a packing of some sort between the plate and the stud itself.
I know you didn't write the bulletin but I would appreciate your thoughts. The "standard" of 316/304 mentioned here got my interest. I will elaborate if necessary.

Thanks for your thoughts AL


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## casey1999 (Oct 18, 2010)

albrazzi said:


> Casey; how do you feel about washers spanning two bolts in a keel mounting system. Specifically my cs30 has three sets of (2) keel bolts and they each share a plate not a regular washer but a backing plate connecting the two nuts. There is a packing of some sort between the plate and the stud itself.
> I know you didn't write the bulletin but I would appreciate your thoughts. The "standard" of 316/304 mentioned here got my interest. I will elaborate if necessary.
> 
> Thanks for your thoughts AL


I see no problem with a washer spanning two bolts- sounds like this type of washer has more surface area than a standard and therefore perform better than a standard washer- that is spreading the load of the keel bolt over the hull. 316 is more corrosion resistant than 304 so always best to use 316 in salt water environment. But seeing J boats are using 304 for the washer only, and the washer can be easily replaced- use of 304 should not be a problem.

On my 37 year old boat the keel bolts/nuts have never been touched. I do not have any keel/hull cracks and the bolts look good. When surveyed 5 years ago the surveyor tapped the keel bolts with a hammer and said they were fine based on the clear ring. I would be hesitant to start messing with the keel nuts as the nut could be seized on the keel bolt, and if I were to get the nut off, I might not be able to seal the nut as good as it is now. Now the J boats may be built less stiff and as the manufacturer recommends, maybe it is a good idea to re-torque once a year.

As far as nut/bolt torque, I never go as high as the bolt chart shows. Even when working on my car the specs call out for much higher torques on some items than I feel comfortable with. I have broken or stripped a lot of bolts when torqueing well below what a bolt torque chart indicates is acceptable. the J boat chart I provide looks reasonable- notice the torque values are well below allowable (less than 1/2 of the allowable torque value).


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## SloopJonB (Jun 6, 2011)

casey1999 said:


> As far as nut/bolt torque, I never go as high as the bolt chart shows. Even when working on my car the specs call out for much higher torques on some items than I feel comfortable with. I have broken or stripped a lot of bolts when torqueing well below what a bolt torque chart indicates is acceptable.


Really, really bad "Internet" advice.

If a fastener breaks below specified torque values it was defective or failing and would have broken or failed in service.

If a factory engineering manual says "XXX foot Lbs" then that is what you should use, not something less that you "feel more comfortable with".

P.S. Spanning two or more bolts with a backing plate is BETTER than single washers, not just "O/K". Wider load distribution is always better than less or narrower.


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## casey1999 (Oct 18, 2010)

SloopJonB said:


> Really, really bad "Internet" advice.
> 
> If a fastener breaks below specified torque values it was defective or failing and would have broken or failed in service.
> 
> ...


Please quote me correctly. This is what I said:
"I see no problem with a washer spanning two bolts- sounds like this type of washer has more surface area than a standard and therefore perform better than a standard washer- that is spreading the load of the keel bolt over the hull. 316 is more corrosion resistant than 304 so always best to use 316 in salt water environment. But seeing J boats are using 304 for the washer only, and the washer can be easily replaced- use of 304 should not be a problem."

And as far as torque values, the charts give maximum. So say your stainless keel bolt has some corrosion or fatigue. Do you really want to torque it to max value a factory new bolt could handle? Do you want to torque over 2x over what the boat yard torqued who built the boat. And torque values depend on fastener thread to thread condition as well as lubrication. Torque to a max value could lead to breakage that benefits nothing. Any way my newest car is a 91 with over 200K miles- do all the work myself and they are more reliable than many new cars- so I'll stick with what works for me.


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## casey1999 (Oct 18, 2010)

If you really want to get technical:
Tightening using the Bolt Head or Nut

When applied torque and the resulting tension (preload) in the bolt are measured during tightening and plotted on a graph, there is a linear relationship between the torque and the tension. The bolt tension is directly dependent, and proportional to, the applied torque. This is illustrated by the graph, which is based upon experimental results, that is shown in the diagram above. From such test results it is possible to establish the appropriate torque for a required bolt preload that may be required.

One of the disadvantages of using torque control is that there can be a significant variation in the bolt preload achieved for a given torque value. There are several reasons for this e.g. inaccuracy in applying the torque, dimensional variations of the thread and hole size variation amoungst others. However, the dominant factor is usually due to the frictional variation that is present between the contact surfaces that are being rotated.

Torque Distribution

From tests, it is known that approximately 50% of the tightening torque is dissipated in overcoming friction under the bolt head or the nut face (whichever is the face that is rotated). Typically only 10% to 15% of the overall torque is actually used to tighten the bolt, the rest is used to overcome friction in the threads and on the contact face that is being rotated (nut face or bolt head). This is illustrated in the piechart shown above. Relatively small changes in the nut face friction can have a significant effect on the bolt preload. As more torque is perhaps needed to overcome friction, less remains for the bolt extension and hence as the effect of adversely reducing the preload. If the friction under the nut face is reduced, then, for a given torque, the bolt preload will be increased.


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## casey1999 (Oct 18, 2010)

Another good article:

Located within arctile:
"Bolt suppliers sometimes have customers say that their bolts are no good because they have started breaking while being installed. Thorough investigation commonly reveals that the customer has started lubricating the bolts to make assembly easier, but maintained to same torque as was used when the were plain finished"

Proper Bolt Torque - by Zero Fasteners

What is the Proper Torque to Use on a Given Bolt 
by Joe Greenslade

"What torque should I use to tighten my bolts?" is a question suppliers of bolts are frequently asked by end user customers. Many times I have been asked if a chart is published on the recommended tightening torque for various bolt grades and sizes. I do not know of any. This article provides such a chart for "Initial Target Tightening Torque. It See Figure 1. The formula for generating these values is explained below.

The widely recognized engineering formula, T= K x D x P (to be explained later in this article), was used to provide the chart's values, but it must be understood that every bolted joint is unique and the optimum tightening torque should be determined for each application by careful experimentation. A properly tightened bolt is one that is stretched such that it acts like a very ridged spring pulling mating surfaces together. The rotation of a bolt (torque) at some point causes it to stretch (tension). Several factors affect how much tension occurs when a given amount of tightening torque is applied. The first factor is the bolt's diameter. It takes more force to tighten a 3/4-10 bolt than to tighten a 318-16 bolt because it is larger in diameter. The second factor is the bolt's grade. It takes more force to stretch an SAE Grade 8 bolt than it does to stretch an SAE Grade 5 bolt because of the greater material strength. The third factor is the coefficient of friction, frequently referred to as the "nut factor." The value of this factor indicates that harder, smoother, and/or slicker bolting surfaces, such as threads and bearing surfaces, require less rotational force (torque) to stretch (tension) a bolt than do softer, rougher, and stickier surfaces. The basic formula T = K x D x P stated earlier takes these factors into account and provides users with a starting point for establishing an initial target tightening torque.

• T Target tighten torque (the result of this formula is in inch pounds, dividing by 12 yields foot pounds 
• K Coefficient of friction (nut factor), always an estimation in this formula 
• D Bolts nominal diameter in inches 
• P Bolt's desired tensile load in pounds (generally 75% of yield strength)

The reason all applications should be evaluated to determine the optimum tightening torque is that the K factor in this formula is always an estimate. The most commonly used bolting K factors arc 0.20 for plain finished bolts, 0.22 for zinc plated bolts, and 0.10 for waxed or highly lubricated bolts.

The only way to properly determine the optimum tightening torque for a given application is to simulate the exact application. This should be done with a tension indicating device of some type on the bolt in the application. The bolt is tightened until the desired P (load) is indicated by the tension indicating device. The tightening torque required to achieve the desired tension is the actual tightening torque that should be used for that given application. It is extremely important to realize that this tightening value is valid only so long as all of the aspects of the application remain constant Bolt suppliers sometimes have customers say that their bolts are no good because they have started breaking while being installed. Thorough investigation commonly reveals that the customer has started lubricating the bolts to make assembly easier, but maintained to same torque as was used when the were plain finished

The table in this article shows that by using this formula a 1/2-13 Grade 5 plain bolt should be tightened to 82 foot pounds, but the same bolt that is waxed only requires 41 foot pounds to tighten the same tension. A perfect 1/2-13 Grade 5 waxed bolt will break if it is tightened to 81 foot pounds because the K factor is drastically lower. The bolts are fine, but the application changed. Suppliers need to understand this and be able to educate their customers to resolve this common customer complaint about breaking bolts.

The chart is provided for quick reference by fastener suppliers and users for selecting an initial target tightening torque. This chart was derived by using the formula shown earlier. An example of the calculation is as follows:

Product: 3/4-10 Grade 5 zinc plated bolt 
Formula: T= K x D x P

• K= 0.22 (zinc plated) 
• D= .750 (3/4-10 nominal diameter 
• P= 23.046 pounds

Hopefully the chart will help suppliers with an initial answer to the customer's question, "What torque should I use to tighten my bolts?" Keep in mind this is only an estimated value. It may provide satisfactory performance, but it also may not. Every application should be evaluated on its own to determine the optimum torque value for each application. Major bolt suppliers should have tension indicating equipment necessary to help their customers determine the appropriate tightening values for their specific applications. Keep in mind that if the lubricant on a bolt and nut combination is changed, the tightening torque value must be altered to achieve the desired amount of bolt tension.

Joe Greenslade is President of Greenslade and Company, Inc. located in Rockford, Illinois. His firm specializes in providing manufacturing tooling and inspection equipment to suppliers of screws, bolts, rivets, and nuts 
throughout the world.

Joe is an inventor, author, and lecturer. He holds eleven US Patents. Has written over 80 technical articles for industrial trade journals, and has spoken frequently at trade association meetings and technical conferences on issues related to industrial quality for the past ten years.


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## albrazzi (Oct 15, 2014)

casey1999 said:


> I see no problem with a washer spanning two bolts- sounds like this type of washer has more surface area than a standard and therefore perform better than a standard washer- that is spreading the load of the keel bolt over the hull. 316 is more corrosion resistant than 304 so always best to use 316 in salt water environment. But seeing J boats are using 304 for the washer only, and the washer can be easily replaced- use of 304 should not be a problem.
> 
> On my 37 year old boat the keel bolts/nuts have never been touched. I do not have any keel/hull cracks and the bolts look good. When surveyed 5 years ago the surveyor tapped the keel bolts with a hammer and said they were fine based on the clear ring. I would be hesitant to start messing with the keel nuts as the nut could be seized on the keel bolt, and if I were to get the nut off, I might not be able to seal the nut as good as it is now. Now the J boats may be built less stiff and as the manufacturer recommends, maybe it is a good idea to re-torque once a year.
> 
> As far as nut/bolt torque, I never go as high as the bolt chart shows. Even when working on my car the specs call out for much higher torques on some items than I feel comfortable with. I have broken or stripped a lot of bolts when torqueing well below what a bolt torque chart indicates is acceptable. the J boat chart I provide looks reasonable- notice the torque values are well below allowable (less than 1/2 of the allowable torque value).


Sorry to ask the same question twice but I understand the benefits of a larger bearing surface for a flat washer backing plate etc. 
I was thinking more along the lines of galvanic action with two SS studs in a lead keel tied together creating a potential either once loosened by service or with a salt bath and some dissimilar metals (alloy grades anyway) after some interesting corrosion on some recently replaced keel nuts.
Don't mean to hijack but the torque values question cant possibly have any more answers out there.


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## casey1999 (Oct 18, 2010)

I don't think the galvanic corrosion would be an issue either between 304 and 316 SS or stainless and lead. Most keel bolt issues are with stress corrosion where the stainless is surrounded by salt water that has liittle or no oxygen, then the stainless corrodes. On a keel bolt this usually happens below the washer, since above the washer the sea water can still have enough dissolved oxygen to allow the stainless to form its thin protective layer that resists corrosion. So by just removing the nut and washer, you may still not see the stress corrosion that would be lurking down the next inch or so in the bolt as you head towards the keel. The only way to know for sure is to pull a keel bolt and inspect. That can be a big job, but one some folks decide to do. Also, for galvanic corrosion to happen between the lead keel a Ss keel bolts, a cell would need to form. The bilge would protect between the bolts and any exposed lead on the outside of keel, and normally the keel bolts are sealed well enough that salt water would not exist all the way from the keel bolt nut to the end of the keel bolt in the lead keel. Even if this case existed, the lead would see the loss of material (corrosion) not the Ss bolt.


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## albrazzi (Oct 15, 2014)

Thanks for your thoughts. My theory was the "cell" is formed by the two bolts (studs) resting in lead and tied together at the washer (backing plate) and the resistance of a loose nut or even a tight one on the contact area between the nut and the plate. I deal with anodes protecting underground pipe lines for a living so I do understand the sacrificial properties of an anode. I saw a comment somewhere in the forums from someone who didn't like tying studs together on keel bolts in this fashion somewhere on this forum but he didn't say why and I cant find it now to ask directly.


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## RichH (Jul 10, 2000)

A LOT of potentially powerful misinformation is being given on this thread.

The advice of following the manufacturers and designers torque loading is a damn good one. 
If that mfg. specification info isnt any longer available, then seek out a specific brand/model owners groups for what 'has historically worked', etc. 
Failing all that above and if youre intentions are being precise, spend the $ and have a licensed structural engineer to calculate the stress to be applied to those bolts.

Only a damn fool will apply MAXIMUM torque to a fastener using 'cookbook' torque values. 
If you set tension to the maximum, there will/may be no 'reserve' strength capacity for dynamic loading (boat heeled over onto its ear, etc.; falling off a BIG wave while heeled), you may exceed the 'dynamic' load capacity of the system including applied 'safety factors' that the designer usually has/ did incorporated into the design: 'customarily' @ SF=2 for 'coastal' design and SF=3 for 'blue water' ... and many designers go 'higher' for such a crit. stress area.

The problem is that when most of these, especially older boats, were designed no one clearly understood the effect of fatigue (endurance limit) of 300 series stainless, and certainly not the affects of 'crevice corrosion' - all potential adverse effects that can weaken the fasteners, the sub-structure and its *function* and component structural integrity.

Rx: Dont blindly 'guess' and dont 'max out' the torque .... unless you by history or spec. manual, clearly KNOW that it should be 'otherwise'.

In probably most sail boat design, how the designer views a keel vs. structural loads is to theoretically heel the boat to about 45° over, calculate the loads required to keep the keel attached and then apply those 'safety factors' on top of the calculated loads - to take care of adverse 'dynamic' and unforseen events happening to that 'joint/bolts/etc.' 
The keel weight/mass adds load, the angle of heel adds 'complicated' loads (especially a keel which is a 'cantilever' - a difficult structure to analyze for dynamic service), falling off a wave while heeled ..... all adds load to the keel bolts. So if one 'strains-up' those bolts to maximum torque, you 'may' be well beyond the service stress capacity (including additive fatigue because those bolts are stressed well above their fatigue endurance limit) of those bolts during those future 'dynamic' and 'unforeseen' events.

If your boat is so old that such 'designers' torque requirements are not available, I would suggest to find that data from a 'very similar' geometrical / shape (keel shape/ weight/ depth and bolting pattern) design and apply those recommendations (from knowledgeable owners and historical performance data/info, etc.) to your boat. 
As I stated if the exact mfg./design values are unavailable - then engineer/designer calcs., then owners group, etc.

Dont 'blindly' torque those bolts to their 'maximum', unless you have 'clear and unimpeachable' information that such has some historical / 'scantling' evidence that this is correct.

hope this helps.


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## casey1999 (Oct 18, 2010)

Here is an excellent thread about keel bolts:

http://www.sailnet.com/forums/gear-maintenance/43505-wet-bilge-more-than-just-nuisance.html

Here is my opinion on the subject:
Why should a keel bolt ever need to be re-torqued? The only reasons I can think of are:

1. The keel/hull joint is compressing so you need to make up for the compression by pulling the keel up (via tightening the keel bolts). Now if this joint is compressing- that to me says this is a design or build flaw with the boat. If designed and built right, the joint should not compress.

2. The keel bolts are stretching. The only reason I can think of that a keel bolt would stretch is that it is overstressed in use (meaning the boat designer/builder did not install enough keel bolts, or the diameter was too small. The other reason may be due to corrosion under the nut/washer, the diameter of the keel bolt has been reduced, thereby increasing stress (psi) and stretching the bolt.

Now in my opinion re-torqueing the bolt is not going to solve anything. It will not correct the problem.

So you constantly re-torque your auto wheel lugs? When was the last time you opened up your engine to re-torque the head bolts? When was the last time all the bolts in the empire state building were re-torqued? If a boat is designed and built right, the keel bolts should never need re-torqueing. Replacing due to corrosion from water in bilge might be a reason to replace.

Here is another thought on re-torqueing keel bolts. What if your bolts are perfectly fine, no hull to keel cracking, a dry bilge and no leaking. Say though, the stainless keel bolt to nut connection is gulled and seized. What is the point of re-torqueing? What might happen is that you strip the nut threads of what was once a perfectly good nut/bolt connection- just because the bolt/nut is gulled and seized does not mean it is not a strong connection.

How many bolts with rusted threads have you broken trying to remove? Now was not that bolt with rusty threads working perfectly fine prior to your trying to remove it? Would there be any point for me to go through my 1991 rusty LandCruiser and re-torque all the rusty threaded bolts to factory spec. I think not, I think she is good at least 200k miles more as is. Attached is pic of my old 1978 Landcruiser- never re-torqued them bolts.


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