How do I find the location of the corners in this print? (Novice Post)

I am getting back into CNC Programming and trying to hone my skills by programming one of the more difficult parts I could find. I am having trouble finding the coordinates for some of the angles and circular cuts, but I can seem to figure out how to find them using trig or by looking at the print. What should I do?

Imgur: The magic of the Internet
Here is a link to a picture of the print. I circled the corners I am talking about.

Although there are many here that use CAD/CAM, you might get more results on the CAD/CAM forum.

bob1352 said:

Imgur: The magic of the Internet

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There's nothing there. I turned off all my filters and everything, still no go.

Just put it here.

And if I caught something, I'm gonna go get covid and cough on you !

Looks like a programming example part

Appears the corner in Y is defined, X might be off the page at the top

From the progression of reference point numbers, the X0/Y0 is in the upper right corner of the part.

All the info you need is there, it can be trigged out, but some of its going
to be tricky, like where you have an angle intersecting an arc.

It actually looks like more of a fun geometry/trig problem than a programming problem.

The way we cheat in the machining world, is we just draw it up and let the CAD do
all the work. That shouldn't take but a few minutes and you'll have everything
you need.

I have never seen a drawing like that before and I wonder just where it came from. My first guess would be a high school drafting class. But there is a NIMS logo on the sheet. I do not like the use of two entirely different ways of showing dimensions. I also do not like the fact that there is nothing to indicate the units of those measurements. I would assume metric, but even then are the numbers mm, cm, m, or km? Perhaps microns?

As far as I can tell and assuming the numbers in the rectangles are dimensions, all the features are located just fine with respect to each other. And the one angle that is on the drawing appears to be referenced to a vertical line.

BUT absolutely none of those features are located with respect to the edges of the part. Nor is there any indication of any point that would be at the center of the overall rectangle. Perhaps that location is of no importance and the overall pattern can be anywhere on the part. Even the sole angle shown is not referenced to an edge. Perhaps the overall pattern can be rotated within any range as long as the overall pattern still fits inside the overall rectangle of the part? Perhaps the designer just assumed that the overall pattern would be centered on the part and some of the lines would be parallel to the edges. But that is just speculation. I consider it to be a great example of how not to draw anything.

The full sheet is not shown so I ask if there is any other information on the sheet that you are not showing? Perhaps in a note?

Another thing is the corners where two straight paths or a straight and a curved path meet are drawn with sharp corners. That is going to be difficult to make without hand work.

Are you not cheating by asking here ?

Better question is, do you need to? The corners in question are mostly where arcs intersect with lines, so they are fully defined by the center location and radius. Can they not be defined that way for whatever you are stuck on? Is it programming you need help with, or metrology to validate a success?

bob1352 said:

but I can seem to figure out how to find them using trig or by looking at the print. What should I do?

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Brush up on your trig. All of the information you need is on that drawing.

What i see is 2.5 x 4 rectangular part with all the features cut down as step. Hence all the chamfers cut on the raised up profile. I tried to draw it up in cad, but couldn't get the numbers to add up. There is something going on that is not obvious to me.

Mtndew said:

Brush up on your trig. All of the information you need is on that drawing.

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Yes it is but I'd much rather just draw it in the CAD and ask it.
When there were only pencil drawing boards it was done the harder way. How much trig on paper is needed to find all these points?
Do you use a sundial to tell time or a sliderule to help trig this out nowadays?
There is the good ole fun side of no CAD and no calculator to solve it but not very time efficient.
Some would say CAD cheating, is a TI-35 also cheating?
Bob
(I did not try to draw it and there are impossible part drawings)

I looked at the photo of PART of the drawing again. I do see a 7 in the second from the top place in the stack of Y numbers on the right. I guess that 7 is referring to the top edge of the part.

However, I still do not see anything on this IMAGE of the drawing to indicate the X location of anything inside the outer edges.

If any of you guys who keep saying that all that is needed is on this image can actually tell the X location of anything, please say so.

EPAIII said:

If any of you guys who keep saying that all that is needed is on this image can actually tell the X location of anything, please say so.

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I thunked we were just crunching the geometry for the profile. There is the bottom of a box
on the -E- datum, I'm assuming its there. I also don't agree with the assignment of B and C and
D and E. D,E should be B,C and vise versa. But that has nothing to do with figuring out the profile.

I think a clarification from the customer is in order......oh wait there is no customer.....

first practice on this:

"99 Percent" Miss This. What Is The Length? - YouTube

I have easily found the X in that internet puzzle using CAD.

IIRC, it is 8+ inches. However, I have not found any shortcut that makes doing that calculation without CAD possible. I look at it from time to time but I have not looked at the video for the answer.

OK, making the assumption that the missing X dimension really is on the drawing, just out of the part that was posted, and looking at the geometry of the pattern I started to draw the pattern with my CAD. I started at what is the 0,0 coordinate at the upper right and drew the (90°?) arc that is closest to that starting point. Then I wanted to draw the horizontal line from the arc's upper-left corner. But I only have that starting point. There is no way to locate the end point of that line. It meets another arc with a 27 (mm?) radius but the two are not drawn as tangent and the center of that 27 mm arc is not shown in any obvious way. The radius line simply terminates at the outline of the part. It is difficult to see if there is a center indicated at that edge, but even if there is, you still need the missing X dimension to that part edge and it is NOT shown on the part of the drawing that is in the image the OP provided.

So, I repeat my statement that "If any of you guys who keep saying that all that is needed is on this image can actually tell the X location of anything, please say so." ALL the information that is needed to just work out the pattern is NOT shown in the photo posted. I need that missing X number to draw just the second element of the pattern. Who knows what else may be missing. So, my CAD drawing of the pattern had to stop after just ONE element.

I think the OP did not spend much time looking at the drawing because if he had, he would have realized that the missing X number is of vital importance. So he did not ensure that it was in the photo of the drawing.

Another problem exists at the right end of the arc at the bottom which is apparently centered at -45, -80. Again, the photo cuts off a vital piece of information, it's radius. And, even with that radius, the right end of that arc is not well located. One could assume that it is at the same, -50 Y coordinate as it's left end is, but that would only be an assumption. A 74.482 mm(?) dimension at a -35° angle is shown and I guess, with some trigonometry, the X-Y coordinates of that point could be found. This is really a poor way to dimension this.

dian said:

first practice on this:

"99 Percent" Miss This. What Is The Length? - YouTube

Click to expand...

If someone handed that drawing to me and wanted me to make the part, either by manual of CNC methods, I would ball it up and throw it back while shouting as loud as I could that they should take some lessons in mechanical drafting.

That shouting would include some carefully chosen words of the four letter variety.

If I was forced to make it, I would make it plain that I was going to bill at my highest rate for every hour or fraction thereof used to interpret the drawing and that I would not be the least bit responsible for any errors anywhere in the process.

EPAIII said:

..... This is really a poor way to dimension this.

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If you think this bad you should try making form tools for screw machines.
The fact that the end of the leader for rad size on the bottom cut off in the picture is for sure a problem.
The rest of it not so bad.
We will often dimension complex form wheels in a similar ordinate fashion.
Places like Cranden have no problem, some others come back crying and want dimensions double specified which is never good sign.
While doable It would be quite the challenge to trig it out by hand using paper and pencil with the non-tangent rads. A whole lot of triangles.
I do agree that it is messy.
Bob

EPAIII said:

So, my CAD drawing of the pattern had to stop after just ONE element.

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I had the same problem.After I drew the 63.5MM x 101.6MM I started to run into problems with the numbers.
So it was one and done for me also.