Wood and Steel

try rec.crafts.metalworking

Before your question can be answered, its dimensions must be known as well as the type of steel. If your concerned with corrosion on your hinge, consider stainless or having the item plated.

Joe G

A lot. It will depend on your plane of forces, and clearances, and a bunch of other parameters, but the tensile strength of "typical" steel is around 60kpsi.

If you are making a hinge for some sort of door, the steel is probably not going to fail. It depends on how you plan to form the loops. Or are you thinking an interleaved plate and pinning the whole thing? In which case it will be the shear strength of the pin, not the plate. Or...

If this is strictly indoors, and not a humid environment rust should not be a big concern. But if you would be concerned about staining, a simple blackening would be good. Or a clear coat if you like the natural steel look.

JW

Tue, Feb 26, 2008, 9:02am (EST-3) snipped-for-privacy@ulvr.com (julvr) doth posteth thusly: I'm creating Should I be worried about rust? (this is for indoors only). Also, does anyone know how much wieght a .25" piece of steel can withstand before shearing?

How should I know if you should be worried about rust? Me, I'd paint whatever and not worry about it.

A 25" piece of steel what? Tubing, flat sheet metal, your hinge?

I'd say do like you've been advised, go ask the metalworking guys. But when you do, give them DETAILS, don't leave all the details out like you did here. On the other hand maybe those guys read minds, I don't.

JOAT

For most environments, no. But a quick coat of clear lacquer will help prevent rust.

Need more information. Google "Strength of Materials." Keep in mind that not all steel has the same strength.

1. Use stainless if you are worried about rust... But don't try to drill it until you check out the RPM rate calculations at
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   Stainless basically can NOT be drilled without some sort of oil coolant on the bit... Unless you have a machine that spins at 25 RPM. :)
2. Shearing? Lots... Maybe. Depends on how it will be taking the load. All at once in a bust of energy or hanging weight, etc... If it shears, aluminum wouldn't have worked for you nayhow unless it was 3X the size in all dimensions (general rule of thumb comment, not set law...)

Regards, Joe Agro, Jr. (800) 871-5022

Sorry, I guess I didn't mention the .25" steel was the intended diameter of the pin. After some looking I worked it out that a .25" steel rod has a shear strength of about 350 lbs -- more than enough (especially as each hinge has two joints, and there are two hinges, which would mean that I have an effective shear strength of about 1400 lbs. I only need about 300lbs, which means I could concivably use Aluminum as well).

As far as lacquer goes, I think the stress between the pin and the housing will remove any finish I attempt to put on, though thanks for the suggestion. I may try to find a coated metal rod to use as the pin, though this still doesn't help me with the housing (which needs to be drilled). I'm hoping that maybe a bit of grease will help here

-- if not, I'll have to replace it down the road.

John

Send it out an have it plated. You will pay a premium for a small quantity of a couple pieces but if its a concern, which it seems to be, a few bucks for plating wouldnt be out of line.

Mark

Of course I could determine that if I only knew the rest of the dimensions. You left out a few things to say the least. However, as I am retired, I don't do that sort of thing anymore.

Jim

Tue, Feb 26, 2008, 5:59pm (EST-1) snipped-for-privacy@nospam.com (Jim) doth ssayeth: You left out a few things to say the least.

Yep, details. They always leave out the details.

JOAT

You can always blacken the steel and clear coat it to protect it.

Kate

Also, does anyone know how much wieght a .25" piece of steel can withstand before shearing?

Thanks,

John

At the risk of sounding like a smartass... if you put a wee bit of oil or white grease on the hinge, it will not only swing smoother but it will resist corrosion.

Another nice finish on steel is an oil finish. Pretty common too.

Kate

As far as lacquer goes, I think the stress between the pin and the housing will remove any finish I attempt to put on, though thanks for the suggestion. I may try to find a coated metal rod to use as the pin, though this still doesn't help me with the housing (which needs to be drilled). I'm hoping that maybe a bit of grease will help here

-- if not, I'll have to replace it down the road.

John

I think your calculation is a little off. As I recall a rough estimate of shear strengh of steel is 2/3 of tensile strength. Tensile strength of mild steel about 70,000 psi, someone correct me if I'm wrong, but I'm sure I'm in the ballpark for magnitude. Area of 1/4" circle is pi*0.25^2= about 0.19 sq in. 70000 * 2/3 * .19 = about 8800 lbs, That seems a little high perhaps, but 350 pounds is sure not going to shear a 1/4 bolt.

You need to use the radius rather than the diameter, Larry, which would drop it to about 2200 lbs, but it's still far more than adequate for his purpose.

John Martin

As it turns out, I was using half of the radius :). I was also using a tensile yeild strength of 40000 psi (which is the pressure at which mild steel deforms)...

Based on the updated calculations, Aluminum should work fine, and then there are no rust issues -- A tad pricier, but I'll swallow the costs.

Of intersest, The shear strength of a size 8 steel screw should be about 320 lbs. That's a lot stronger than I thought! (of course, if you overtighten the screw, then it might be less, as then you have introduced a tensile force... and of course, the shear strength would be increased by the friction of the two materials being held together... Hmmm.. not that useful of a number after all... :) )

John

Oops! Good thing I'm not an engineer!