engine bolts - high tensile?

[slimtim]

aha! Thanks for that. I have just found out the same info. high tensile ss doesn't seem to exist (although one bloke told me it does, but is very rare and expensive). I phoned up a place and they told me that ht carbon steel has the same tensile loading (800Nmm) as the A4 "high STRENGTH" stainless bolts. Also, carbon steel is brittle which means it is less resistant to shear than stainless bolts.

So the conclusion I have drawn is that if I get A4 high strength ss bolts, they will be just as good in tension and even better in shear than the high tensile carbon steel bolts!

I also phoned up tohatsu and they can supply 4 bolts, 4 washers and 4 nuts for just under £50. This is what is normally supplied with an engine.

Tim

[roycruse]

50 quid is stil 5 X what you need to pay though - id opt for your local steel fastening place - just makle sure its A4 marine grade and your laughing

[roycruse]

http://www.a2a4.co.uk/acatalog/A2A4_...EADED_428.html

http://www.a2a4.co.uk/acatalog/A2A4_...READED_80.html

I think these guys will have everything you need when it comes to stainless steel bolts - they have UNF and UNC threads aswell if you want to go down that route.

And at just over a £1 each i dought they will be beaten on price

[Hightower]

Higher strength Stainless bolts have some Titanium in I think, this is why they're so expensive!!

[Dirk Diggler]

Originally Posted by roycruse

I think these guys will have everything you need when it comes to stainless steel bolts - they have UNF and UNC threads aswell if you want to go down that route.

And at just over a £1 each i dought they will be beaten on price

Excellent little shop in Shirley, but they wont have what you want! All the M12 they sell is a coarse thread, and you need a fine thread, which is why people talk of "unf"!

[Cookee]

If anyone has a source of M12 metric fine or UNF 1/2" I would be gratefull!

[Pete7]

Foulkes & Son (The Barge)
Riverside Yard, Blundells Lane, Bursledon, Southampton, Hampshire SO31 1AA
Tel: 023 8040 6349 Classification: Boats & Smallcraft

http://www.mycartel.co.uk/m/listing.php?id=728109

Boxes of the stuff, full thread and bolts with shoulders, but don't tell everyone

Pete

[slimtim]

Originally Posted by Dirk Diggler

Excellent little shop in Shirley, but they wont have what you want! All the M12 they sell is a coarse thread, and you need a fine thread, which is why people talk of "unf"!

Ok, why do I need fine thread? If its to stop them coming loose, if so, I was going to use nylock nuts. If its for some other reason...what is it? I spose someone might say that the finer thread is stonger because there is more contact area, but is that really the case? There will be more threads, but they are all smaller.

I think I'll probably get the bolts from tohatsu...can't go wrong then

Tim

[Richard B]

Nylocks are good. Double nuts locked back to back are good too. Have you measured what length bolt you need and what length thread you need? You will need the thickness of the transom + thickness of the engine saddle + nut (and washer) thickness. Also add the thickness of any anti-theft device that you may fit. Then you'll be surprised that many bolt stockists (like A2A4 for example) don't have suitable bolts

[Rogue Wave]

Dirk really does know his stuff, if he suggests UNF then just go get em I prefer nylocks to backed together nuts but whatever you choose a little splash of loctite would not hurt

[Jono]

Originally Posted by roycruse

STOP ! DONT SPEND 100 QUID

I have just spoken to 2 local steel merchants / suppliers.

There is no such thing as high tensile stainless steel.

There are 2 grades of stainless steel A2 and A4.

A4 is the marine grade stainless steel which just so happens to be higher tensile steel than the standards A2 but is not as high tensile as Hight Tensile steel.

It is perfectly possible that the mention of High Tensile Stainless is refering to A4 marine grade stainless.

Any way DUTCHY FASTENERS (01872 573999) (http://www.duchyfasteners.com/) have M12 100mm A4 Grade stainless bolts for around £2 each in stock.

First off..find a new fastener supplier that doesn't talk out of his arse....

** Stepping onto hobby-horse**

The designation A2/A4 is actually only part of the designation of a fastener. The important bit, in terms of strength is the second part, which is often left off. A "proper" code would be something like A2/50 or A4/80.
50 is lowest strength 80 is highest. They are in Newton/MM squared and the numbers represent 1/10 of their strength.

A4/80 is 316 (16/10/2) stainless with a tensile of 800 N/mm2

A4 is not a "better" grade than A2, it's just different and has different chemical properties. A4 is a 316 material, A2 is 304 type (or 302 if yer a yank..). 316 having added Molybdenum content and increased Nickel (hence more money..) which is good for corrosion resistance against certain substances such as chlorides. Hence the use in marine environments.

8.8 marked bolts have tensile of 800ish N/mm2
10.9 = 1040ish
12.0 = 1270ish

**stepping off hobby-horse **

Hope that helps y'all out...

[Jono]

Originally Posted by slimtim

Ok, why do I need fine thread? If its to stop them coming loose, if so, I was going to use nylock nuts. If its for some other reason...what is it? I spose someone might say that the finer thread is stonger because there is more contact area, but is that really the case? There will be more threads, but they are all smaller.

I think I'll probably get the bolts from tohatsu...can't go wrong then

Tim

I thought you were a "student engineer" ? You fell a sleep through yer lectures or what?

Thread pitch is different for a whole variety of reasons connected with material compatability, expected loadings and use. Consider how much less torque is required on a fine thread fastener to obtain the same "clamping force" as opposed to coarse thread, therefore you can obtain higher clamping forces before you reach the point where the torque required to turn the fastener exceeds the strength of the bolt to resist your attempt to twist its little head off....
S/steel fasteners are also "rougher" than C/steel, so won't acheive the same clamping force for torque applied..

...and please don't re-use fasteners that are "torqued up" good 'n tight.. use new ones every time

[slimtim]

Originally Posted by Jono

I thought you were a "student engineer" ? You fell a sleep through yer lectures or what?

There may have been a few occasions where I may have been feeling a little "under the weather" in a 9 o'clock lecture I'm all graduated now though.

I was aware of the increased clamping force you can get from a finer pitch but thought a big old spanner would do a good job Going back a little bit, my dad and I wondered why it was necessary to have high tensile bolts clamping a brittle cast aluminium outboard saddle which would surely fracture before a bolt broke (unless as you say jono, a coarse pitch bolt was damaged through overtightening with a big old spanner!). I assume now that it is purely to be on the safe side and to get as much clamping force as possible.

Thanks for the clarification on the bolt grades, much appreciated. I never really studied bolts specifically (only briefly) but did do a lot on stainless steels.

I have gone for the tohatsu bolts because I can get them quickly and easily from a place near me, and in theory ( ) they should be exactly what I require...fine pitch M12 (although they couldn't tell me what tensile strength they were).

I hope this thread may be of use to someone who is fitting a second hand engine in the future.

Thanks everyone for your contributions!

Tim

[roycruse]

Originally Posted by Jono

First off..find a new fastener supplier that doesn't talk out of his arse....

** Stepping onto hobby-horse**

The designation A2/A4 is actually only part of the designation of a fastener. The important bit, in terms of strength is the second part, which is often left off. A "proper" code would be something like A2/50 or A4/80.
50 is lowest strength 80 is highest. They are in Newton/MM squared and the numbers represent 1/10 of their strength.

A4/80 is 316 (16/10/2) stainless with a tensile of 800 N/mm2

A4 is not a "better" grade than A2, it's just different and has different chemical properties. A4 is a 316 material, A2 is 304 type (or 302 if yer a yank..). 316 having added Molybdenum content and increased Nickel (hence more money..) which is good for corrosion resistance against certain substances such as chlorides. Hence the use in marine environments.

8.8 marked bolts have tensile of 800ish N/mm2
10.9 = 1040ish
12.0 = 1270ish

**stepping off hobby-horse **

Hope that helps y'all out...

where were you at the begining of the thread

You seem to know all there is to know about steel bolts.

Now kindly point us in the direction of some suppliers that dont talk out of their arse so all us ignoramuses dont continue to get fed bulshit...

Thanks

[Jono]

Roy,

That's the easy bit..... www.hydrobolt.co.uk are as good as you'd want. Unfortunately, the bad news is that you will only be (in the nicest possible sense) a nuisance customer to them. I’m not sure what they classify as “minimum” when they specify no minimum order. Ask your local supplier if he will order from them.
Cheers, Jono

[Jono]

Originally Posted by slimtim

There may have been a few occasions where I may have been feeling a little "under the weather" in a 9 o'clock lecture I'm all graduated now though.

Bloody students.. I ask you...

[Pete7]

Originally Posted by slimtim

There may have been a few occasions where I may have been feeling a little "under the weather" in a 9 o'clock lecture I'm all graduated now though.

Excellent, as a fully qualified chartered engineer this country is going to need people like Tim when the oil runs out and we have to start building the next generation of Nuclear Reactors

Pete

[Just as long as they are not built in my back garden]

[Jono]

Originally Posted by Pete7

Excellent, as a fully qualified chartered engineer this country is going to need people like Tim when the oil runs out and we have to start building the next generation of Nuclear Reactors

Pete

[Just as long as they are not built in my back garden]

Ohhh... "chartered" engineer....... not "real" engineer....... now I understand!

Just kiddin' Tim.... I wasn't bright enough to go to Uni....

[Richard B]

Originally Posted by Pete7

a fully qualified chartered engineer...

I would guess that Tim's now a Batchelor of Science or Engineering, (BSc or BEng) and it will be many years of continued experience, study and exams before he, and other recent graduates, reach the position of Chartered Engineer (CEng)!

[slimtim]

Originally Posted by Richard B

I would guess that Tim's now a Batchelor of Science or Engineering, (BSc or BEng) and it will be many years of continued experience, study and exams before he, and other recent graduates, reach the position of Chartered Engineer (CEng)!

Ehem...(climbs on to hobby-horse) First Class Honours Masters Mechanical Engineering - MEng (climbs off hobby-horse) I'll have you know !

Didn't teach me sh*t about bolts though did it?! Takes a good 4 to 5 years to get chartered and I'm not going to be one of those engineers that designs a pile of crap without out a thought about how to use it or maintain it!

Pete, I'll design you a nuclear reactor to fit in your P22 console

Tim