Some advice needed regarding screwing.

[Psychosaffa]

I need to replace 2 bolts that are 1/2 x 8" unf A2 stainless. They are partially threaded and go through 2 cast iron lumps sandwiching a 10mm plate, the ballast on a boat keel.
I can't find 8" bolts, but can find threaded rod. Would threaded rod be fine, or should I really find some partially threaded bolts?

 

[Tinbasherdan]

Can't see why you couldn't use threaded bar myself, if it's only holding some ballast lumps in

 

[rikrobson]

A bolt is partially threaded, whereas a screw is fully threaded.
if you are struggling to fid bots then threaded bar should be fine
have you thought about looking for M12 bolts? There are plenty of metric bolts in ebay.

 

[bs2236]

A2 is not great with sea water, A4 would be better for longevity.

 

[addjunkie]

A2 is not great with sea water, A4 would be better for longevity.

I agee good advice. I assume the bolt has a nut on the bottom.

 

[ratherbewindsurfing]

http://www.westfieldfasteners.co.uk/A4_ScrewBolt_HexHd_UNFine_THRpart_0.5000.html

Bit expensive

 

[addjunkie]

Yachting is an expensive hobby.....

If it flys, floats or has sex, it should be rented!

 

[daleyd]

Some advice needed regarding screwing


You called?

 

[Psychosaffa]

Thanks guys, top notch advice as always!
They bolts are not cheap at all, but rather that than an upside down boat!

Threaded bar works out a wee bit cheaper, is there any objections to using threaded bar instead of partially threaded bolts?

 

[rikrobson]

Threaded bar will be fine. The weakest link is the Threaded section but you still have Threaded section on a bolt.
And it a bolt not a poetically Threaded bolt. Bolts are partially Threaded. A full Threaded bolt is not bolt it's a set screw

 

[Psychosaffa]

Every day is a school day! Thanks chief!

 

[Arclikeharrypotter]

Personally if there is an option for like for like parts then I'd stick with that.

 

[Bill Edwards]

The only problem with threaded bar which seems to apply for steel (no idea about SS) is that it can often be at a much lower tensile grade - somewhere around the 4 mark rather than the standard 8.8.

So just make sure you know what you are buying.

 

[rikrobson]

It's a2 grade so it's a lot less than 8.8 anyway.. it shouldn't matter it its just holding a lump of iron.

 

[500e]

Be careful what you use in Salt water SS can corrode as fast as anything else.
Have seen SS Keel bolts eaten by 50% in 2 seasons.
http://www.bssa.org.uk/topics.php?article=100

 

[macandmoss]

I would go for the high tensile hardened bolts ,if your going to do the job your best to make it last ,check Google for plant / agricultural suppliers near you and take old bolts down or just explain , if they haven't got them in stock they should order them in . Best doing that than seeing what turns up from eBay

 

[wookie]

Would it be worth using some denso paste on the threads before bolting it all together ?

I wondering if it would be a good idea being that it would be underwater but we always use it on bolts holding equipment such as Radar etc to stop them seizing/limit corrosion.

I work with boat electrics rather than the mechanical side so it's a little out of my area of expertise.

 

[BrokenBiker]

IF the old bolts are definitely A2 then i cant see an issue with using A2 threaded rod instead, but prsonally i would use A4 as its more resistent to salt water...

if however the old bolts are 8.8 then id use OE replacements

 

[addjunkie]

Having experienced a knock down on a keel boat, id use the higher grade. The forces in the not expected directions are extreme.

If something like ballast breaks loose, you get a hole or worse. In rough conditions that would be the last thing you would want. Let along a chunk of ballast flying around with everything else while you hang on and hope for the best.

 

[Psychosaffa]

I went for the A4 bolts.
It's on a lift keel trailer sailer so it won't constantly stay submerged and get washed down with fresh water after every session.