Rusty screw replacement

[Stomper]

so I went and searched that and reading different things that stainless screws will corrode aluminum threads but steel screws are worse, zinc plated stainless is ideal I think...

I was a certified outboard mechanic in a former life. I've taken apart lots of aluminum engines where someone replaced an OEM stainless screw or bolt with a carbon steel one. It ain't pretty. There's a reason outboard manufacturers go to the extra expense of using nothing but stainless screws and bolts on aluminum engines.

Dissimilar metals, (nonferrous and ferrous) contact will cause (corrosive) electrolysis. There are many grades of stainless steel, the "lower" (although structurally stronger) grades will be magnetic because it's chemistry is still in the ferrous "range". Just make sure the stainless screws you use don't get picked up by a magnet and you'll be good to go using them on aluminum.

 

[ZigZagZeke]

Dissimilar metals, (nonferrous and ferrous) contact will cause (corrosive) electrolysis. There are many grades of stainless steel, the "lower" (although structurally stronger) grades will be magnetic because it's chemistry is still in the ferrous "range". Just make sure the stainless screws you use don't get picked up by a magnet and you'll be good to go using them on aluminum.

What you want for this application is SS316, not SS304 or some other composition. You want the higher nickel content in 316. The chromium content is about the same across most "stainless" steel.

Stainless Steel Composition What Is It? - thyssenkrupp Materials (UK)

Our handy Stainless Steel Composition tables will provide you with a breakdown of some of the grades we have to provide. This is a really useful guide.

www.thyssenkrupp-materials.co.uk

 

[ZigZagZeke]

Dissimilar metals, (nonferrous and ferrous) contact will cause (corrosive) electrolysis. There are many grades of stainless steel, the "lower" (although structurally stronger) grades will be magnetic because it's chemistry is still in the ferrous "range". Just make sure the stainless screws you use don't get picked up by a magnet and you'll be good to go using them on aluminum.

Warning, Geek Rant:

The Seebeck effect (electrical potential across dissimilar metal junctions) is actually used to measure temperature, particularly in molten metal (e.g. lead, steel, aluminum), since it is a more or less linear function across various temperature bands. An iron/copper junction will produce voltage in the millivolt range that is proportional to the temperature it's exposed to. In a typical "millivolt" gas furnace the thermocouple, an iron/copper junction, produces enough current when heated by the pilot light to keep the main gas valve open and allow the furnace to work.

To bring all this back to guns, when you have an aluminum scope body and rings, and you put a steel screw in the rings to secure the scope, you have created a dissimilar metal junction which can cause current to flow in the metal. Add a little moisture and you can have very bad things happen.

 

[Koda]

I love reading the technical replies to selecting proper metal type for the screws.

So last night after Velseys tip I emailed Warne, they replied this morning and are sending me new screws in the mail. Super easy and awesome customer support, no questions asked. I just told them my screws were rusted and asked for replacement and its on the way.

So the next question then is, will the new screws also rust. Probably not... small chance. Not all the screws in the mounts are rusted so odds are I got a few bad samples back when I purchased the rings. I also have another hunting rifle with Warne rings that arent rusting so far.

Seems like I can replace the screws with Warnes new ones, if they rust in another year or two I can probably search this forum for this thread and just go find the proper stainless screws. Im not certain I see any compelling evidence to ignore Warnes screws and go custom? As long as their plating is good they wont rust or cause electical corrosion between the steel screw and the aluminum ring threads?

 

[Stomper]

Warning, Geek Rant:

The Seebeck effect (electrical potential across dissimilar metal junctions) is actually used to measure temperature, particularly in molten metal (e.g. lead, steel, aluminum), since it is a more or less linear function across various temperature bands. An iron/copper junction will produce voltage in the millivolt range that is proportional to the temperature it's exposed to. In a typical "millivolt" gas furnace the thermocouple, an iron/copper junction, produces enough current when heated by the pilot light to keep the main gas valve open and allow the furnace to work.

To bring all this back to guns, when you have an aluminum scope body and rings, and you put a steel screw in the rings to secure the scope, you have created a dissimilar metal junction which can cause current to flow in the metal. Add a little moisture and you can have very bad things happen.

Yeah, I use type-k (bimetal) thermocouples to record temperature readings all the time. LOL.

 

[Koda]

Grant it Warne is located in just the next town, but they had the new screws to me the next day. I replaced them tonight. When I was looking up the torque to use I noticed the rings I bought are steel, not aluminum....
sorry for any confusion on all the metalurgical science.

heres a pic of the old rusty screws and how bad they are. Purchased new 2 years ago this month, used only 2 deer seasons. Im hoping the replacements are plated better.

 

[kmk1012]

Grant it Warne is located in just the next town, but they had the new screws to me the next day. I replaced them tonight. When I was looking up the torque to use I noticed the rings I bought are steel, not aluminum....
sorry for any confusion on all the metalurgical science.

heres a pic of the old rusty screws and how bad they are. Purchased new 2 years ago this month, used only 2 deer seasons. Im hoping the replacements are plated better.
View attachment 1073679

With two separate lengths, are they a different ring from front to rear?

 

[Koda]

With two separate lengths, are they a different ring from front to rear?

no, Warne Maxima rings are split vertically so the bottom screws are longer than the top screws for each ring.

213M Warne 30mm, PA, Low Matte Rings

The 213M Maxima scope rings from Warne Scope Mounts feature a wider band (more contact gripping surface) and premium materials for outstanding performance.

warnescopemounts.com

 

[kmk1012]

no, Warne Maxima rings are split vertically so the bottom screws are longer than the top screws for each ring.

213M Warne 30mm, PA, Low Matte Rings

The 213M Maxima scope rings from Warne Scope Mounts feature a wider band (more contact gripping surface) and premium materials for outstanding performance.

warnescopemounts.com

Dang, shows what I know, which can be very little at times! Only reason I brought it up was long ago I had issues with zeroing a scope on a friends ago and realized that he had four different types of screws in the rings. It was impossible to obtain the same torque value with all the variables going on there.

 

[Ura-Ki]

I'll check them out, if I get lucky and they have my screw then cool. if not I'll probably just go the easiest route with stainless. Thanks for the tip.

What part of OryGun you reside in? If your anywhere near Potland, Park Rose Hardware is your GOTO for any type of fastener, especially gun screws, they even match with old Winchester and Colt Screws which are Unobtanium!

 

[Koda]

What part of OryGun you reside in? If your anywhere near Potland, Park Rose Hardware is your GOTO for any type of fastener, especially gun screws, they even match with old Winchester and Colt Screws which are Unobtanium!

So actually I contacted Warne and they sent me a new hardware kit the next day, free. Its good to know about Park Rose hardware, its cool that hardware stores are selling gun screws.