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  • hwingo
    replied
    Originally posted by boslab View Post
    You do get different properties depending on rolling direction, it looks like the peice is in the rolling direction, it's rolled, wound on a coil, then pulled from the coil and passed through a straightener, on thick stuff it can be just a pyramid set up, 2 rolls one side and a roll in the middle the other side and sheared into sheet size, the straightener puts just enough deformation to get the sheet flat, when you slit a straightened sheet it often reverts to the curve that was present before the straightener.
    Cutting at 90, ie across the coil or 90 degrees to rolling often limits this, there is a tendency to bow but across a narrow strip it's not noticeable.
    Cutting at 45 degrees to the rolling axis often leaves a twist...........................
    Mark

    Hi Mark,

    I really didn't know the particulars but I suspected, when you suggested trying a different cut, that bowing may have something to do with the way the metal was finalized. That's interesting. Thanks for pointing that out.

    Harold

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  • Normanv
    replied
    Many years ago, when I was building a steam locomotive, I found that the BMS 1 1/4" x 1/4" that I was using for the connecting rods had lots of built in stress. I was horrified to see how it peeled open as I cut down the side of a 230mm piece. The cut opened out to 10mm as I proceeded down the edges. Fortunately this only happened as I roughed it out, it stayed straight during the subsequent machining.

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  • boslab
    replied
    You do get different properties depending on rolling direction, it looks like the peice is in the rolling direction, it's rolled, wound on a coil, then pulled from the coil and passed through a straightener, on thick stuff it can be just a pyramid set up, 2 rolls one side and a roll in the middle the other side and sheared into sheet size, the straightener puts just enough deformation to get the sheet flat, when you slit a straightened sheet it often reverts to the curve that was present before the straightener.
    Cutting at 90, ie across the coil or 90 degrees to rolling often limits this, there is a tendency to bow but across a narrow strip it's not noticeable.
    Cutting at 45 degrees to the rolling axis often leaves a twist.
    Steel is the same, there are 3 axis, the steel industry call them R1, 2 and three but all the plants I went too call R1 rolling, R2 is 90 degree to rolling and R3 45 degree to rolling displaced in the rolling direction, we did come up with a R4 which was 45 degrees the other way or rolled, the steel is tested in all these directions with tensile test pieces being cut in these directions, the results are usually quite different so manufacturers can cut pits of car out of one sheet with different mechanical properties, same applied to Ali sheet, not saying that's universal but fairly in Europe. Eg land rover, jaguar and so on
    Mark

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  • hwingo
    replied
    Originally posted by boslab View Post
    If you have the bit of sheet it came out of you might try cutting one at 90 degrees to the first.
    Mark
    Hi Mark,

    Should I expect a different result if cut at a 90 deg angle? Is it remotely possible that internal stresses run at a different angle? What should I be looking for or what different results should I expect or observe?

    Harold

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  • boslab
    replied
    If you have the bit of sheet it came out of you might try cutting one at 90 degrees to the first.
    Mark

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  • hwingo
    replied
    Hey Guys,

    I tried the "arbor press method" and it worked well enough to permit drilling and tapping. All went well and my project, though not complete, is on the way to completion. Once the rail was installed I squared all four sides of the plate with the rail and everything fits nicely. The next phase is to fabricate a protractor which will allow me to obtain various angles for grinding my lathe bits.

    Many thanks to all for helping me to get to this point. ALL suggestions were very helpful and much appreciated. With further progress, I'll post my results.

    Thanks,
    Harold

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  • ptjw7uk
    replied
    Turn strip upside down, position and clamp at each end drill and tap in the middle - then work outwards until the clamps cannot be used!

    Peter

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  • jhe.1973
    replied
    Hi Harold,

    I would stay away from any heat to try and bend the aluminum. It would be WAAY too easy to end up taking all the 'heat treating' out of it and ending up with dead soft aluminum. Not very wear resistant if soft.

    If you try the arbor press method (my first choice) I would use as hard a pieces of rubber at the ends & middle - something like auto tire hardness. The ram of the press and the supporting blocks might leave dents otherwise.

    Another trick that will definitely work is to use a smooth, shiny ball end of a ball peen hammer and by supporting the side you show as the top on a flat piece of steel, tap the opposite side all along the center towards each end making sure the supporting steel is directly below the hammer.

    The idea is to lengthen the bottom side by squeezing/stretching the metal a small bit on one side only w/each tap. You are not trying to bend the metal with the hammer. This will leave small dimples but that side can become the one in contact with your larger plate.

    You may be surprised just how easy it is to move the metal with rather tiny dimples, not by blasting away on it.

    By supporting the 'long' side on a flat surface, you are assured of distributing the forces and concentrating the stretching on the side where you want it.

    I've straightened 2.5 inch diameter SS shafts this way w/o resorting to a massive press.
    Last edited by jhe.1973; 03-10-2015, 04:06 AM.

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  • hwingo
    replied
    Originally posted by elf View Post
    Why do you have to remove the clamps before drilling and tapping operations?
    The clamps I have are too large to fit on my table and mill vise.

    Harold

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  • elf
    replied
    Why do you have to remove the clamps before drilling and tapping operations?

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  • hwingo
    replied
    Hi Paul,

    The 1/4" edge is facing the camera. If I could push that down only 2.5mm and get it to stay then I would have it. That's not gonna easily happen. Will either have to slot the rail that's bowed or bend like suggested ...... or possibly a little of both. Once the bowed piece is closer to the plate, JB Weld will easily hold the track-rail in place allowing me the opportunity to drill and tap all the holes.

    Harold

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  • Paul Alciatore
    replied
    Which edge is facing the camera in this photo, the 1/4" edge or the 1/2" edge?

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  • JoeLee
    replied
    Try slotting or cutting it with a thinner jewelers saw. I think what is happening is there is some stretching of the alum. due to the width of the cut and that is causing your cut strip to bow. You may be pushing through more than cutting through the material. Also I would wet it down with WD 40 as you cut. I don't know what your DOC is per pass.

    JL................
    Last edited by JoeLee; 03-09-2015, 10:27 PM.

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  • hwingo
    replied
    The width of the slitting cutter is 3/32". Both ideas of either using the arbor press or making cuts in the metal are viable options of which I had not considered. I like both approaches.

    The images shown below may help to visualize some of what I am wanting to do.

    The bow is shown in the first image. The greatest amount of bow is 2.5mm. The second images shows the grinder’s table and slot.
    Harold





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  • JoeLee
    replied
    What I would do, since this is giving you trouble is cut it part way through on the table saw, just to score maybe .010 per pass half way through and then bend it back and forth until it breaks off, then mill it to finish width. Just allow yourself an extra 1/6" or so. 6061 shouldn't curl up. What is the width of your slotting cutter???

    JL..............

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