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What's the point of this screw?

  1. Dec 10, 2012 #1

    Femme_physics

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    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Dec 10, 2012 #2
    Hello FP, welcome back.

    Perhaps it was an attachment point for a securing line?

    Perhaps it is a cover for an oiling gallery into the journal bearing?
     
  4. Dec 10, 2012 #3

    Ranger Mike

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    the small hole is to indicate that it should be toward the front. With unskilled assmebly workers, simply tell them hole towards the frame hole..Note offset of bolts..my opinion
     
  5. Dec 10, 2012 #4
    Agree with you Ranger Mike, however to use this as an indicator is sketchy, the unskilled labourer could put the part on the other side of the beam, with only the faces facing the front but the part could be on the other side...
     
  6. Dec 10, 2012 #5

    jedishrfu

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    I'm thinking its there to indicate the second drawing is a side projection and not a top projection.
     
  7. Dec 10, 2012 #6

    Ranger Mike

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    The drawing is not exactly per typical industrial standards,, in my opinion since the side front view is bass acwards. And the small hole is NOT detailed and if it is NOT A THRU HOLE then the idea that it is an assembly aid may be in effect.
     
  8. Dec 10, 2012 #7

    SteamKing

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    IMO, the hole at 1 is drilled so that a shackle pin or some other load supporting mechanism can be attached to 2. There is no indication that hole 1 is to be threaded after drilling, thus I would not expect a screw to be used. From the note attached to the bottom, one can expect a load of 16 kN to be applied at this point in the direction indicated by the arrow.
     
  9. Dec 10, 2012 #8

    Ranger Mike

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    I don't put much credence in the whole drawing specifically because the side view shows the flange mounted on the out side ( note phantom line showing frame line). The front view shows the flange mounted on the inside so the draftsman ( opps ..what is the new PC term we use now...) who drew this does not know proper mechanical drawing skills to begin with. Your guess is as good as mine as to function of the two small IDs
     
  10. Dec 10, 2012 #9
    Where are you guys seeing an assembly aid?

    The OP is talking about the large through-hole on block 1. OP, just because nothing is going through the hole in the picture, doesn't mean there never would be anything. Could be a mounting bracket for a small sheave, could be to hang things on, could be anything.

    The drawings shows a force of 16kN in the downward direction. In reality, how do you think this load would be applied to the bracket? You might say clamps, but if we are talking reality, I don't see why somone would install a bracket and then clamp to it when they could have just clamped to block 2 anyway.
     
  11. Dec 10, 2012 #10

    jedishrfu

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    this type of bracket is used in some garage door mounts with an arm connected to the motor.
     
    Last edited: Dec 10, 2012
  12. Dec 10, 2012 #11
    The idea that people were thinking the marker at the end of 1 (the pinhole looking bit) was the hole in question didn't even occur to me until you pointed this out. The responses make a lot more sense now vs. "why is that 3rd hole there" which to me is a fairly easily answered question -- because something not shown in the diagram attaches there.
     
  13. Dec 10, 2012 #12

    Averagesupernova

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    It's been a while since I actually had to do any drafting but IIRC the drawing is correct. Don't we imagine the view to the right of the other view as if the part were hinged into the paper on its right side?
     
  14. Dec 10, 2012 #13
    Yep, for americans at least. We use the right hand rotation rule.
     
  15. Dec 10, 2012 #14

    Femme_physics

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    I'm told, according to this exercise from a machine parts textbook, that a screw is supposed to fit there. My goal is to pick the correct metric screw according to calculations (which I won't do here), I was just confused why there need to be a screw there to begin with. A screw is supposed to FASTEN two parts or more together, not just fill in holes for no apparent reason. :-/
     
  16. Dec 10, 2012 #15
    You were to pick the correct bolt for that hole, or for the two upper holes?

    If it's a textbook, sometimes they just want to test your knowledge of the subject matter. If there is a 16 kN load, perhaps they want you too demonstrate your comprehension of the section by correctly sizing a bolt to support the load (say, if you were to assume 16 kN down shared on both shear planes or something).
     
  17. Dec 10, 2012 #16

    Femme_physics

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    For that one hole, Travis. Yes, of course they want to test my knowledge, again my great bafflement here was with the respect to the fact that it would be much more effective to create this part without that hole that I'd have to chose a screw for. A screw doesn't seem to prove any useful purpose.
     
  18. Dec 10, 2012 #17
    The part would be useless without that hole. As others have said, the hole is for the attachment of something -- something that is not shown on the drawing.

    Perhaps you are thinking that this bracket is unnecessary -- the load could be attached directly to a hole in the beam. While possibly true, we do not know the factors leading to the initial design. For example, the beam might be used for multiple purposes, each requiring a different attachment design; The beam may not have the required physical properties to support the load at a single point; The item to be attached may need to be located a specific distance away from the beam.
     
  19. Dec 10, 2012 #18

    I like Serena

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    Suppose you had an object (with a weight of 16 kN) that you'd want to fix to the bracket.
    It could have a hole just like the one in part 1.
    Perhaps even using the same part.
    Then you could fix them together with the same type of screw that is used in part 2.
    This screw would probably have to be twice as strong to be able to bear the weight.
     
  20. Dec 10, 2012 #19

    Femme_physics

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    Alright, the explanations seems reasonable enough :) I am a bit confused as how to pick a screw who does not connect 2 surfaces together only 1 with the formulas I'm working with but I'll leave that question to my teacher :) I appreciate your time in getting through to my thick skull!
     
  21. Dec 12, 2012 #20
    The hole could very well be a clearance hole. The end of the screw might connect to another part not pictured.
     
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