Help with Mechanical Assembly Drawing (N3) [Solved]

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This question was sent to us by Phyllis of Tshwane South College who was having trouble with this mechanical assembly drawing (N3). Herman van der Merwe is the IDT expert answering the question.

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    We received this enquiry from Phyllis from Tshwane South College – it’s a Mechanical Drawing Assembly consisting of nine parts.  Which is item 1, the Frame, item 2 the V-Belt Pulley, item 3 the Flat-Belt Pulley, item 4 the Bush, item 5 the Cover Plate, item 6 the Shaft, item 7 and 8 is the locking pins, and item 9 is an M10 bolt.

    The parts are given in a first angle orthographic projection, showing you all the details of item 1; showing the front view and the left end view of the parts; your belts, the pulleys and all the pins.

    The important part to remember of this is, ‘what is the main primary view that you’re looking at’? In this case, item 1 is the main component to which all the other parts attach.  So this is where you start your drawing and your most important section of the assembly.

    I’ve taken the liberty and modeled up all the parts as they’ve required.  Item 1 being your frame.  Your shaft; your Flat-belt pulley; your V-Belt pulley; the Bush; the Plate and the bolts.  And there we have our two Lock-in Pins.

    The question that they’re asking is to draw a full sectional front-view of the assembly.  The other two parts they require are the title and the scale below your drawing (that’s carrying two marks).

    There is however one small little error on the question – as you have an M10 bolt, your tapped hole on the frame is an M10, but the cover-plate has a radius 4 bolt which gives you a diameter 8 hole so it won’t fit.  So I assume that would be an error and that would be a diameter 10 hole on that plate.

    The easiest way to figure out how to assemble these parts is to look at common sizes.  For example we’ve got a 10 diameter shaft and on the flat-belt pulley you have a 10 diameter hole.  The shaft on the back end is a diameter 20, and the v-belt pulley has a diameter 20 hole. Similarly, the bush has a diameter 20 hole which will fit in there.

    Look at the space in between the two tapped holes which should be the same on your cover plate.

    This is basically the final drawing that they require – a full sectional front view, which means that all the components that are cut through need to be hatched.  We do not hatch a shaft, or fasteners or webs.  In this case the two pulley’s are hatched; the bush is hatched; the cover-plate and the frame is hatched.  The bolt you’re not going to see because the bolt is in the background so you don’t show hidden detail on a sectional view, and the shaft we’ll show as if it’s not cut because we don’t cut a shaft. The only time we’ll cut a shaft is if you’re doing a partial cut-away to show a keyway or a bolt-in detail.

    The other two parts they require is the title and the scale below the it.  The title will be 5mm text and the scale will be 3mm text.

    Phyllis I hope this answers your question and… Happy Drawing!

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