SS vs Mild Steel rule of thumb?

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henro
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Joined: Tue Apr 01, 2003 2:40 pm
Location: Near Pgh, PA

SS vs Mild Steel rule of thumb?

Post by henro » Sat Feb 07, 2004 10:34 am

Hi,

I have been unsuccessful in finding the answer by searching. I guess the question makes it obvious that I am a woodworker! [img]/ubb/images/graemlins/blush.gif"%20alt="[/img]

Is there a rule of thumb that can be used to compare a tool's rating, when is given in mild steel, to get an idea what that tool might be able to do if stainless is used?

For example, would an electric hand shear rated to cut 16 gage mild steel be expected to cut 20 gage stainless 304 sheet?

How about for bending? If a hand brake is rated in mild steel, say 18 gage, what thickness of SS might it be expected to bend? 20 gage SS? 22 gage stainless?

Thanks for any help! [img]/ubb/images/graemlins/smile.gif"%20alt="[/img]

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Jacin
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Location: Near Cleveland, Ohio

Re: SS vs Mild Steel rule of thumb?

Post by Jacin » Sun Feb 08, 2004 12:41 am

Some of the machine's I am familiar a wee bit with have shearing ratings given in material TENSILE STRENGTH versus THICKNESS.

A specific machine example is:
For instance 50,000psi material cutting capactiy of 9/32 - however 100,000psi material cutting capacity of 3/16

So it ISN'T appearing quite as simple as plain old simple math - BUT keeping it conservative and using common sense will probably keep you out of trouble!

Another example is that if you look in Machinery's Handbook they list (at least my 14th addition does) SHEAR Strength which closely resembles TENSILE strength BUT NOT exactly - some materials have shear numbers HIGHER than TENSILE numbers while other materials are the other way around!

FWIW they list Stainless(and plain old steel) as having the SAME valusies both Shear and Tensile (Steel is different than stainless number wise - but the SHEAR and TENSILE numbers are same for EACH - for instance Stainless might list 120,000psi shear & Tensile while mild might be 60,000psi shear and tensile.

BUT!!!! WAIT!!!!!
Most machines give ratings as "MILD STEEL" which is QUITE a bit lower than OTHER forms of steel (50-60K (psi) - ALLOY steel may be TRIPLE the TENSILE rating - STAINLESS might be quadruple of double or ??? It ALL depends on the ALLOY and HEAT TREAT.

So unfortunately your answer is gonna require some additional research on your part in terms of material - remember the "factory" likes to give ratings in the most "favorable" light.

Another typical rating is my hand held nibbler - rated 10 ga. Steel (mild) and 12ga Stainless (304??) - while another one is 10ga and 14ga respectively - go figure.

I doubt this was the kinda answer you were looking for, but hey I tried!!

Good luck!

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henro
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Location: Near Pgh, PA

Re: SS vs Mild Steel rule of thumb?

Post by henro » Wed Feb 11, 2004 10:00 am

Jacin,

Thank you for your reply. [img]/ubb/images/graemlins/smile.gif"%20alt="[/img]

At this point I think I will just use the following "Henro's Rule of Thumb" when considering a tool rated for mild steel, when I want to apply its use to SS:

1) Reduce mild steel rating by 50% for stainless and you will probably be OK, and your tool will probably handle SS sheet at half the rated thickness.

2) Reduce mild steel rating by 25% and you might be OK...if you cross your fingers correctly and hold your mouth right. Your tool will tell you if it does not like what you are doing, sooner or later... [img]/ubb/images/graemlins/blush.gif"%20alt="[/img]

If tool breaks when in mode 2), change to mode 1)

If tool breaks when in mode 1), buy tool rated for SS

If the cheapest tool is still expensive, buy the proper tool to begin with and don't rely on "Rules of Thumb!" [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]

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