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Thread: 55t press

  1. 26th August 2012, 09:01 PM #71
    uninformed
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    Quote Originally Posted by slug_burner View Post
    Give the intermittent (stitch/skip weld) a try. It is a good way to limit distortion by reducing the heat build up. I'd say you would be doing well to distort 16mm FB. Set it up, tack weld it in a few places, then start extending your weld from the tacks. If you work from either end and one stitch on each side of the 75 x 12 FB you will not cause enough distortion to worry you.



    I suspect that you might make it easier if you bring the 75 x 12 FB in from the edge then you will not have to worry about having to prepare the outside corner for welding.

    The thing will still be able to be disassembled, you will just have an angle or Tee like angle to transport instead of just FB. I think that the welding route will be quicker than drill and tap.
    If I weld it on both sides, either "angle" or "T", I will have to grind flat the side that the PFC's bolt to. This also means I cant really bring it in from one edge if I want good access to the pin bolts that will be in the center of the 100x16.

    I am familiar with Stitch welding and backstepping....
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  2. 27th August 2012, 08:30 AM #72
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    Twisting

    What are the thoughts on reducing/controlling the twisting of the HEAD PFC's with the ram mounts?

    Im thinking of welding in web stiffeners (75x10 say) to the HEAD PFC's, each end, 100mm in from each end and at 1/3 and 2/3 spacing along its length. These being welded to top/bottom flanges and web. They will only be welded to the PFC they are in. The ends of the PFC will be tied (bolted) together with the end plates.

    Im thinking of locating the PFC top and bottom flange with the ram mounting plate, by fastening flat bar to it (mounting plates) on the inside and outside of the flanges, giving say 0.5mm gap. If this is done top and bottom and both sides, along with the top and bottom plate being bolted together via long HT threaded rod, Im hoping this will also help with twisting and deflection, rather than having to again weld the 2 PFC's together.....
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  3. 30th August 2012, 06:06 PM #73
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    depth of thread?

    When drilling and taping a hole in mild steel to accept a high tensile bolt, how much thread engagement is required? I'm guessing its a ratio based on dia.....
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  4. 31st August 2012, 06:18 AM #74
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    Quote Originally Posted by uninformed View Post
    When drilling and taping a hole in mild steel to accept a high tensile bolt, how much thread engagement is required? I'm guessing its a ratio based on dia.....
    1.5D is the accepted depth for most threads.
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  5. 1st September 2012, 03:04 PM #75
    Dougal
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    Quote Originally Posted by rick130 View Post
    1.5D is the accepted depth for most threads.
    Up to 3x for really soft stuff. 1.5 is good for everything else. Go 2x if you're feeling nervous.
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  6. 1st September 2012, 04:12 PM #76
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    Quote Originally Posted by Dougal View Post
    Up to 3x for really soft stuff. 1.5 is good for everything else. Go 2x if you're feeling nervous.
    Yep, used to use 2.5D with Helicoils into aluminium.
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  7. 1st September 2012, 05:23 PM #77
    Dougal
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    Helicoils are a god-send.
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  8. 2nd September 2012, 04:13 PM #78
    uninformed
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    picked up a bit more steel. Also quick rough set up of where im headed with the head beam and mounting to give a visual idea....





    The top plate is 300mm wide and 25mm thick. obviously it needs to be bored for the ram to pass through.
    Last edited by uninformed; 9th January 2017 at 07:10 PM.
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  9. 2nd September 2012, 10:26 PM #79
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    Is that your final planned orientation of the PFCs? It was mentioned earlier that to help remove twisting, they should be facing the other way...

    Quote Originally Posted by Bush65 View Post
    PFC (and angle) sections are not symmetrical so their shear centre is offset, resulting in torsion when load is not applied through the shear centre. For a 250 PFC the shear centre is about 30 mm from the back of the web. For this reason you should arrange the pair of PFC's so their toes are pointed out, i.e. ] [ You will also have to restrain the PFC's to resist twisting – weld something between them, near the supports at each end, and if it can't extend for the 250 depth, then it should at least tie them together at the top and bottom.
    I'm hoping turning them round won't affect the design too much. I'm also not sure how important it is to put them round the other way... Again, I'm not a qualified engineer!

    I'm looking forward to seeing the final product coming together. It's certainly an interesting and useful project.

    -Martin
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  10. 3rd September 2012, 11:58 AM #80
    uninformed
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    Again, I had not ignored nore missed what John had said. But as Im not 100% on why and how the PFC's are twisting, I cant say whether or not the way Im headed will work or fail.

    nothing is final until it is done .... but it is my planned way of doing it for the head beam only. Now what you see in the picture isnt complete. There would be some flat bar, say 75x10 bolted to the top and bottom plates, inbetween the PFC's. This, along with the 32x10 FB on the outsides, will "lock in" the top and bottom flange of the PFC's. There will also be 4 x M16 or so, threaded rod connecting the top plate with the bottom plate. When the ram is in the desiered position, they get tighten up/down hard. In the ends of the PFC, will be some 100x12 FB welded from top to bottom flange, hard up to the web, then bolted to these will be some 250x10 Flate plate that will connect the PFC's to each other. The PFCs, being inside the uprights and bolted through the web hard to uprights.....

    clear as mud hey
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