What type of stainless, please?

[PaulRainbow]

Huge thanks.

M8's are what held the old Barient 24s, but, you're right, the Barients were mounted with six screws, against just five in the Lewmars.

I'll go up to M10s (edit: asssuming the holes in the winch base will take M10s. I'll have a look this afternoon).

M8 are the correct bolts, they should be countersunk though. The company i suggested on Ebay stock them.

 

[NealB]

M8 are the correct bolts, they should be countersunk though. The company i suggested on Ebay stock them.

Thanks again, Paul.

The holes in the Lewmars are too small for M10s, so I'm happy to trust the Lewmar design engineers' judgement on size.

And, a big YES, too, to the need for countersunk.

 

[NealB]

Westfield fastners are my usual supplier of choice. I'd tend to go A4 / 316. You'd probably be ok with A2 in that location but I usually just go A4 anyway.

Thank you.

I suspect that, like you, I won't be able to resist the psychological lure of 316, just for the sake of saving a few quid.

 

[vyv_cox]

Thank you.

I suspect that, like you, I won't be able to resist the psychological lure of 316, just for the sake of saving a few quid.

As suggested earlier there are various strength grades in 300 series stainless steels. The standard annealed stuff is 50, but there are also mechanically strengthened grades 70 and 80. So either A2 80 or A4 80 would give even more confidence

 

[NealB]

As suggested earlier there are various strength grades in 300 series stainless steels. The standard annealed stuff is 50, but there are also mechanically strengthened grades 70 and 80. So either A2 80 or A4 80 would give even more confidence

Thanks vyv ...... what a resource this site is for an engineering numpty like me.

 

[Rappey]

M8 sounds skinny for 43s. They can take an enormous load.

That made me think as I've fitted 46's with m8 hex bolts with a washer to bridge the countersink hole.
Googled, and a m8 stainless grade 50 hex bolt shears around 18.3 kn. Thats 1866kg, x 5 bolts = 9330 kg.
Either your overthinking fancy fittings or there is something im missing ?

 

[AngusMcDoon]

Googled, and a m8 stainless grade 50 hex bolt shears around 18.3 kn. Thats 1866kg, x 5 bolts = 9330 kg.
Either your overthinking fancy fittings or there is something im missing ?

The bolts won't be in pure static shear as the load's point of action is above the bolts' bearing surfaces. There will be all sorts of tension and bending going on as well, and cyclical loads as the winch is used leading to the possibility of fatigue cracking. If the bolts are clamped down near to their plastic limit the clamping force induced friction between the winch base and its mounting surface will take the bulk of the sideways load. However, bolted through GRP, it being flexible and not very strong, it's unlikely that the bolts will be able to be torqued near their plastic limit (especially countersunk head ones) to get a high clamping load.

 

[Neeves]

The bolts won't be in pure static shear as the load's point of action is above the bolts' bearing surfaces. There will be all sorts of tension and bending going on as well, and cyclical loads as the winch is used leading to the possibility of fatigue cracking. If the bolts are clamped down near to their plastic limit the clamping force induced friction between the winch base and its mounting surface will take the bulk of the sideways load. However, bolted through GRP, it being flexible and not very strong, it's unlikely that the bolts will be able to be torqued near their plastic limit (especially countersunk head ones) to get a high clamping load.

There is also an assumption that all 5 bolts take any tensions equally - which seems most unlikely.

J

 

[vyv_cox]

When I upgraded my genoa winches many years ago I was intending to buy Lewmar 43s. The time was just as Gibb went out of business and the chandlery had a pair of their 52s at a very knock-down price. We bought them and installed them with M8 stainless bolts. They have never given any cause for concern.

 

[NealB]

When I upgraded my genoa winches many years ago I was intending to buy Lewmar 43s. The time was just as Gibb went out of business and the chandlery had a pair of their 52s at a very knock-down price. We bought them and installed them with M8 stainless bolts. They have never given any cause for concern.

Thanks again.

 

[NealB]

When I upgraded my genoa winches many years ago I was intending to buy Lewmar 43s. The time was just as Gibb went out of business and the chandlery had a pair of their 52s at a very knock-down price. We bought them and installed them with M8 stainless bolts. They have never given any cause for concern.

Did you use 50, 70 or 80?

So far, I've tried four potential suppliers, looking for M8 A4-80 bolts. They can, of course, all get 80, but only as a special purchase for at least 100 bolts. I only need ten.

Are 80 (or 70), 'overkill'?

Presumably, if I can find 80, then the nuts and washers should also be 80?

 

[Wansworth]

Whatever you choose, put some anti seize lubricant on first...newly made stainless bolts can gall....in effect weld themselves before they are fully seated...then life as you know it ends, while you spend all your time figuring out how to remove them

Gall….interesting word

 

[rogerthebodger]

Gall….interesting word

My understating is the word should be galling

gall is bold and impudent behavior: or the contains of the gall bladder

Gaul is a reign of Europe

 

[vyv_cox]

Did you use 50, 70 or 80?

So far, I've tried four potential suppliers, looking for M8 A4-80 bolts. They can, of course, all get 80, but only as a special purchase for at least 100 bolts. I only need ten.

Are 80 (or 70), 'overkill'?

Presumably, if I can find 80, then the nuts and washers should also be 80?

Mine are A4 50 as far as I know. It's a very long time since I saw them!

 

[vyv_cox]

My understating is the word should be galling

gall is bold and impudent behavior: or the contains of the gall bladder

Gaul is a reign of Europe

Stainless steel nuts and bolts can gall.

E.g.
Galling is serious…but there are solutions - Stainless Steel World

Standard fasteners prone to galling​

Standard stainless steel bolts and fasteners have a tendency to gall under certain conditions due to their specific properties.

 

[NealB]

Mine are A4 50 as far as I know. It's a very long time since I saw them!

Thanks again!

 

[Bouba]

Gall….interesting word

Galling isn’t it

 

[penberth3]

My understating is the word should be galling

gall is bold and impudent behavior: or the contains of the gall bladder

Gaul is a reign of Europe

to gall = galling. English grammar.

 

[Bouba]

Stainless steel nuts and bolts can gall.

E.g.
Galling is serious…but there are solutions - Stainless Steel World

Standard fasteners prone to galling​

Standard stainless steel bolts and fasteners have a tendency to gall under certain conditions due to their specific properties.

That’s actually an annoying article....you think it’s going to give you the secret of removing a galled bolt....when all it does is show you how to prevent it....well if we remembered that in the first place we wouldn’t be squeezed into the tightest place on the boat armed with every cutting tool we possess scratching our heads and nuts

 

[vyv_cox]

That’s actually an annoying article....you think it’s going to give you the secret of removing a galled bolt....when all it does is show you how to prevent it....well if we remembered that in the first place we wouldn’t be squeezed into the tightest place on the boat armed with every cutting tool we possess scratching our heads and nuts

That's galling for you! There is no removal process. Galling is welding of the asperities on opposing parts. When my babystay bottlescrew suffered the condition I put the body in a vice and used my 24 inch adjustable on the screw flats, with absolutely no success.