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Thread: Steel material that is magnetic and stable when machined

  1. #1
    Associate Engineer
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    Steel material that is magnetic and stable when machined

    Hello-
    I am designing a series of inspection plates for a family of aluminum parts. I want the plate to be steel so that it won't wear when switching out batches of parts. I don't really need a super hard steel, just as long as its togher thatn aluminum. I would like the steel to be stable when machined and magnetic, so that a grinder can be used to achieve the .0004in./3.0X3.0in. flatness tolerance that I need. Right off the top of my head, 416 SS is the only steel that would work, but its pretty pricey.
    What other steel is magnetic and will stay stable when machined?

    Thanks!

  2. #2
    Technical Fellow jboggs's Avatar
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    Dear battleship81, if you look thru this forum you will notice that there is one response that is by far and away the most common first response to initial questions. Guess what it is... Picture please! We need a diagram, sketch, drawing, something to plant your vision you see so clearly in our heads. For example: what is an inspection plate? How big is it? How thick is it? Why the focus on stainless? All these factors will effect the answers you get.

  3. #3
    Administrator Kelly Bramble's Avatar
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    I don't think 416 SS is magnetic.. Check out tool steel A2, A3, A4.... A10.

  4. #4
    Associate Engineer
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    Hi-
    The inspection plate will hold an array of 25 machined, cylindrical (2-3 in. o.d., .375 in. tk.) aluminum parts. The plate will hold each part in a 3 pt. kinematic seat machined into the surface of the plate. The part will lay flat on the plate, and the kinemtic seat in the plate will hold the part on a critical (datumed) plane. The part will not be constrained diametrically, but will be loosely clocked using a locator pin to mate up into one of the tapped holes of the part. A bar will span the part, contacting the part near the "i.d." so as not oil can the bottom surface of the part as it will be constrained axially by a screw that runs through the bar and part and threads into a machined hole in the plate (not pictured).

    There is no focus on stainless, but I need steel thats stable when machined (to hold flatness tolerance), steel (to wear well when switching out batches of aluminum parts), and magnetic so that a grinder can hold the part and be used to achieve the .0004"/3.0X3.0" flatness.

    I had considered 01 tool steel, but I couldn't confirm whether or not it is magnetic, and I know it would be harder to machined than the 416 SS.

    The part in the picture is just a concept test that holds one of the aluminum parts.


    Capture.jpg
    Last edited by battleship81; 06-25-2013 at 12:46 PM.

  5. #5
    Lead Engineer RWOLFEJR's Avatar
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    Ask me and I'd say ANY steel will be stable enough for what you're doing and the question would be more about durability. A good shop won't have any issue making you a flat plate out of any flavor material. I'd look at pre-hard 4130 or 4140 (about 28-32 Rc.) It's relatively inexpensive and machines nice. Buy your stock heavy by at least 1/8" or let the machine shop tell you how much stock they'd like to have to get precision you're after.

    If you want to go top shelf in the durability department at a reasonable price I'd go A2 (very stable in heat treat and one of the lower cost alloys with high hardenability...) Rough machine with about .01 stock for finish grind. Heat treat (supported) and temper to about 45-50 Rc... then finish grind. (I wouldn't go full hard.)

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