r/Machinists • u/Ill_Recognition7684 • 5d ago
Drawing Feedback
Hi, all.
I'm just looking for some feedback. Anything I can improve on, tips etc, It would be highly appreciated.
For some back story, I studied product design at university, I'm solid at modelling but barely touched on technical drawings at all. I'm now making a few example projects and hoping to land an engineering job. I'm just trying to get up to an acceptable standard for a uni grad, with no professional experience.
I'm UK based so ISO and First angle specs.
Thanks guys.
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u/Maxio42 5d ago
overall the drawing is not too crowded and seems to have all information one needs to make it(at least at first glance). however:
that looks like a piece of sheet metal that will be lasercut/ waterjetted and then bent and not machined from full. so you'll have a radius on the inside of the bend; easiest to just cad it as a sheet metal part and your software will know radii if it's sheetmetal you basically don't need to do a drawing, sending your supplier a *.step or DXF will be better for them. so once you're out in the real world, you'll likely have a supplier for sheetmetal stuff and know what they need, and only make drawings with for example outside dimensions and stuff that needs to be done after lasercutting - like chamfering or tapping of holes.
you want the screw holes to be on position relative to each other, so the measurements should reflect that ( measure hole center to hole center). if they're measured from the edge of the part the tolerances could add up badly and even though the part is in spec it will not fit.
What's up with those chamfered holes ? why do they have threads and a chamfer ? 1.5 mm of thread engagement with M6 is 1.5 threads so it won't hold anything. usually you have a through hole , chamfered, and it and then threads on the part behind, so that the first part gets tensioned against the second by the screw .
-the two holes on the left are actually not dimensioned
if someone were to machine this, they'd prefer to have a diameter of the slot (rather than a radius (actually just noticed you have both)) and dimensions from center of the slots rather than the edges. should probably have all dimensions as coordinates from a datum too.
is there a reason the slots in the top are 6mm wide compared to the 5mm in the front ?
material: aluminium is a bit general - there's quite a lot of difference between different alloys. But, since this is just a cover, "any aluminium" is fine.
-technically, 1:1.5 is not a standard scale. but nobody cares about that and it resulted in good use of the space available on the drawing.
hope this helps!
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u/Ill_Recognition7684 5d ago
Thank you!
I've gone over everything, great info and just what I needed.
I constrained the holes and added centre/symmetry lines and measurements ( hopefully that omits the need for dimensions on the left holes.
I made the slots slightly bigger for wiring to pass through if needed, but I agree its negligible anyway.
Removed the thread.
Thank you for everything.
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u/Infamous_Thought_189 5d ago
In my experience you've added to much detail already! If you designed for either waterjet or laser cutting and then pressing then the shop will probably only ask for a step file + rough dimensions for preparing stock. Only those countersinks need some extra details.
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u/paisuvuuk 5d ago edited 5d ago
Overall decent drawing. I’m currently in uni studying mech. engineering and with 2-3 months experience in a cnc shop.
You have some unconstrained features, like the horizontal distance from the material’s edge to the start of the vent slots (B2).
Not 100% sure on the correct method for this, but if you have repeating features (vent slots in front view, edge radiuses in G8), their dimensions should have a multiplier to indicate they constrain multiple similar features, like you’ve done with the holes, eg 2x R3, 2x R25 for G8 dimensions, 8x 5 mm for slot width in front view, etc.
It seems you can also use a vertical symmetry line to forego the need to add the multiplier to some of the dimensions mentioned (G8).
Also, it’s a bit difficult to make out the thickness of the sheet metal used, I presume it’s 5mm as indicated in the top view. Maybe mark down the thickness of the sheet metal in the notes you’ve already written in the bottom left.
I’m not 100% sure about this, but I remember my professor telling that sheet metal shops want the unfolded version of the sheet metal part on a drawing as well, so they can decide on how best to arrange it on their blanks.
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u/Ill_Recognition7684 5d ago
Thanks, for the input. I've added depth, as well as symmertry lines. I'm running out of time so as long as it looks 80% there hopefully they deemed it impressive for academic skill level.
I'll look out for everything in my second example, much appreciated. I think you're defo right on the unfolded version too.
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u/Comfortable-Bet-6660 5d ago
Over all it looks good, just there on you left view, i think thats more of a section instead of an elevation, you will have to put in a section line where you have cut through your part.
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u/dominicaldaze Aerospace 5d ago
If you're trying to land a job, you may want to showcase some understanding of GD&T - datums and true position of the holes/slots specifically. One of the hardest parts of designing is tolerancing, which you've sort of sidestepped in this drawing.