I am updating an old drawing. how would I apply gdt for the holes they want to be .060 tir
Pick one hole for datum and apply GDT to the other, similar as the one below (for total run out)
Exactly what Christian said. I would also consider changing that bolt circle from a radius to a diameter as well but that could just be my preference.
The PDF presented does not indicate there are two holes as there is no depth call-out. The assumption when design checking that this 2X is an error. However. 2X or not:
Where are the
I'm not sure if you guys understand, this is a sheet metal hopper, the holes are on each side, they want the 4 .25 holes on one side to be .060 tir with the .25 holes on the other side. can I use the 1.28 bc as a datum?
Attached is some GDT reference info for you to use in the future. The color chart is particularly useful I think.
I just noticed that in the original dwg they have the top holes on one side marked A and the lower holes on the other side marked B
The holes you have marked are the Ø0.25 holes when I think you want to mark the Ø1.78 holes instead.
Thanks for sharing
I guess they want to mount a shaft/pin between the 2 holes so they want to control the runout between them. You can use the center line between the 2 holes for a datum (best) or you can use either hole to be a datum (hard to inspect)
Here is my suggestion:
another thing I see in the front view is that they have a centerline thru the center of the 1.78 holes. is the concentricity from the center line?
It's just for a position of the .25 holes and has nothing to do with TIR
Look at the color chart I attached above to see what concentricity means. Pic below for reference.
Be careful to use the concentrcity since 2 sections might be concentric but overall might be run out
I'm sure they just want the holes on one side to be in line with the other side
see if my dwg will do that, also how do I position the datum a so it means the center line of the 1.78 hole not the surface
Below is how I would do it. I know it is not perfect as I did it in MS Paint
You want to modify the dwg the way you think correctly or just want to translate from the note on the dwg to GDT symbol?
Practically, how the guys on the floor inspect it?
From the PDF File, seems to me that they want to control the runout the holes on both sides and they might mount a shaft/pin which they can use for inspection?
you might be correct but from the PDF file, seems to me that they ref. to the .25 holes, not 1.78 holes
yes I want to translate their silly note to modern GDT
chris, I'm not trying to figure out what concentric means
Actually, the note totally makes sense to me if they want to mount something between the holes
Here is how you add a datum to to center of the 1.78 hole
You can save the PDF file as bitmap file and embed into a SW dwg so you can add the symbols easily
I am far from an expert, and I am surprised someone more knowledgeable than me hasn't said something. My understanding is Concentricity is difficult to inspect and rarely called for, unless you have a really good reason to control median points. The symbols that folks have been adding are for total runout, which is different from runout and concentricity. My guess is that none of these would be appropriate for a sheet metal part. Position is the callout you will want.
Scott, your aren't being helped by the initial drawing. You are going to have to do some reverse engineering and figure out what this part is supposed to do.
I have not had a lot of GDT training and not taken any classes since High School (many years ago before we even USED computers) but what I remember and what I have been taught by machinists and highly educated mechanical engineers, is to dimension features on the view that shows the features (as you have done) - not to look through a part and try to dimension the features on a different side or view.
I don't know what the "Right" answer is regarding this but you should be able to compare your drawing view to the same relative part view and be able to measure or inspect any feature that is on that side. Exceptions would be a hole or feature that exits that side that was fully defined on another side so it would be redundant on this face (example - a hole drilled from the other side that was fully defined on the other side and as to position, depth, or any required GDT and is just exiting on this face).
The holes in question in this Hopper drawing are separate holes on separate surfaces so they should be defined separately as you have done. If they need to be Concentric or have a limited runout then that should be figured into the dimension tolerances or shown referencing a datum or similar.
If I remember, I will bring up this example with a GD&T Trainer/Guru in my user group (Thomas Allsup ) and see what he would do.
chris I like your solution but the 1.78 holes are just clearance, the 4 .25 holes are the what we are trying to control, heres what I did, what do you think
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