Question about drawing annotations and countersinking in 2d

[Behemothrex]

Hey guys,

 

Doing my Autocad homework and I have run into a snag. I am doing orthographic reproductions of a given drawing.

 

First one of the annotations on the drawing reads.

 

3x Ø.25 THRU V Ø.50 X 82°

 

Okay how I read this is 3 countersunk holes inner diameter is .25 outer diameter is .50 and the angle between the larger hole to the inner hole is 82 degrees.

 

Now in the drawing I am referencing it clearly shows the countersunk holes.

 

But if I try and make the angle from the larger hole to the smaller hole 82 degrees it makes the countersunk basically a cone that penetrates the entire length of the piece. But in the drawing it appears that the countersink is very shallow.

 

So I am in a quandary.

 

I have attached the drawing and basically I just guessed at the countersunk depth of the one that is complete.

 

Any suggestions would help.

 

Thanks

 

Edit: while I have your attention also on the front view of the piece do I need to show a hidden line for the arc that is in the part. I put in one, but not sure if that is the correct way to represent that type of feature.

countersunk.dwg

[JD Mather]

Your angle is 91°, not 82°.

Wrong line type. (should be hidden)

Extra lines in RS view and missing countersink hidden lines.

The hole (ellipse) is shown correctly in RS view.

 

and yes, you need that hidden line in FV for the "negative cylinder" feature (hole going through the part.)

[Behemothrex]

Thanks JD,

 

Yah all the work with the holes was incomplete as I was trying to figure out how to get the 82 degree angle.

 

I saw your example but I guess what is throwing me for a loop is if I do 82 degrees from the outside diameter of .50 it doesn't want to intercept the inside diameter line until its almost at the bottom of the part. Making more of a cone than an countersink.

 

I guess an easier way of asking this would be is there anyway using projection lines to get the depth of the countersink?

 

Maybe I am figuring the angle using the wrong points. I was simply going by the top of the part, or the horizontal line representing the top then going 82 degrees down from that.

 

Hmmm

[Dadgad]

The angle which is described by that value is further clarified in the image.

It represents the number of degrees between the cutting edges of the tool which creates the countersink.

[JD Mather]

You have the circles projected correctly (see magenta lines).

 

Select one of the projection lines and then select the end grip (now highlighted red).

Right mouse button and select Rotate.

Rotate the line -41°.

Repeat with the other line, this time rotating +41°.

Now extend the two lines till the meet in V shape and then trim the excess.

 

[Behemothrex]

 

THANK YOU!

 

JD, and Dadgad you are gods!

 

You not only understood what I was trying to convey in my post, a brilliant feat in itself. But you were able to explain it to me so I could comprehend it.

 

Dadgad the explanation how to find the angle and more importantly what the angle was measuring was a great light bulb moment.

 

And JD your technique for creating the countersink was another ahaa moment. I knew it had to be easier than I was making it.

 

Taking courses online can be a bit confusing at times especially since the book I am using has yet to even mention the annotations its using on the drawings LOL.

 

Oh well that is why I come to the pros, thanks again guys, this site is wonderful not only for the forums but for all the other resources.

 

Once again thank you both!

 

Oh here is the completed drawing, do I need any kind of centerline in the front view representing the center point of the half circle cut out?

 

countersunkcomplete.dwg

Edited October 20, 2012 by Behemothrex

[JD Mather]

Change the lineweight on your layers and it will look better when printed.

Good job on first part.

 

[Behemothrex]

Thanks again JD,

 

These are just going to be e-mailed to my instructor, no printing as of yet, and we have not even talked about using line weights other than default, so if he wants them changed it will be news to me. I am sure I will have more questions later, have a great day and thanks again.