Silicon Bronze 651 or 655??

[endoftheroad]

I am installing new seacocks and am ordering the thruhull bolts.
I have heard before here on this forum 85-5-5-5 or something like that.
Now when I'm ordering screws I find fastener supply houses offering 651 and 655 bronze.
I believe so far from my researching that 651 is lower silicon which gives the alloy it's strength and 655 contains higher silicon.
I think 651 is what we use for seacock screws.
McMaster-Carr

Please correct me if I'm wrong.

But where does 85-55-5 come into play?

Thanks
endoftheroad

[delmarrey]

Originally Posted by endoftheroad

I am installing new seacocks and am ordering the thruhull bolts.
I have heard before here on this forum 85-5-5-5 or something like that.
Now when I'm ordering screws I find fastener supply houses offering 651 and 655 bronze.
I believe so far from my researching that 651 is lower silicon which gives the alloy it's strength and 655 contains higher silicon.
I think 651 is what we use for seacock screws.
McMaster-Carr

Please correct me if I'm wrong.

But where does 85-55-5 come into play?

Thanks
endoftheroad

85-55-5 bronze is for valves, pumps, thruhulls and other casted fittings but not for fasteners. It can crack if too much stress is applied.

[endoftheroad]

Delmarrey,
I just looked into that. I think it has something to do with the lead added for machining.
Thanks a million.

I feel comfortable buying the 651 bronze fasteners.

[Watercolor]

As far as I know all American made bronze seacocks are made of 85-5-5-5 (nominal values 85% copper, 5%tin, 5%zinc, 5%lead. This is also known as Alloy No.836, leaded red brass or composition Bronze. A few of the ball valve manufacturers use either a brass (red or yellow)and some SS for the ball (chromed) and stem.

Spartan uses all 85-5-5-5 except for the SS bolt that holds the handle on.

And you're correct. The 85-5-5-5 is far more malleable, the lead allows for easier machining and therefore lower cost.

I think the 651 is better known for nuts and bolts than 655.

[Cheechako]

a word of caution, although i like bronze screws, they will twist off/break remarkably easy... you kind of have to develop a touch for it... but if you are predrilling holes... you've got to get that hole just right!

[ShipShape]

Originally Posted by Watercolor

As far as I know all American made bronze seacocks are made of 85-5-5-5 (nominal values 85% copper, 5%tin, 5%zinc, 5%lead. This is also known as Alloy No.836, leaded red brass or composition Bronze. A few of the ball valve manufacturers use either a brass (red or yellow)and some SS for the ball (chromed) and stem.

Spartan uses all 85-5-5-5 except for the SS bolt that holds the handle on.

And you're correct. The 85-5-5-5 is far more malleable, the lead allows for easier machining and therefore lower cost.

I think the 651 is better known for nuts and bolts than 655.

I think he was requesting info about screws to secure his new seacocks to his new backing plates. He doesn't know to save money and use 18-8 stainless, which is perfectly adequate for the job, except for maybe seacocks submerged in a wet bilge, which of course is his fault and even bronze screws (or seacocks) won't resist galvanic corrosion under that condition.

He's busy hauled out learning about his choices for this haul out, he's not reading these posts.

[endoftheroad]

Thanks,
delmarrey,
Watercolor and
Cheechako

Your contributions have helped me very much.


Thanks,
endoftheroad