Drawing dimensioning issue

[Anonymous]

I am trying to dimension (in Fusion 360) to the profile of an arc at a specific diameter.  It does not appear 'Edge Extension" goes from a line to an Arc (unless I am missing something).  Is there an easy way to dimension this?

[jhackney1972 · Accepted solution]

I do not think you are missing anything.  Dimension Extension only work when applied to linear elements.  I would use a model "free" sketch to define the location where the two arcs meet.  You can then also add reference dimensions to this line if desire as reference.  Most of the dimensions needed are the location of the arc centers and radii.   You did not supply your model so I tried to approximate one of my own.

[shadow.realm]

How about  putting a dimension something like this

[jhackney1972]

What about it?  You seem to have the dimension placed.  I assume the part is not round because you do not have either a centerline or another view to describe it.  The dimension you have defines a location from the bottom and a width at that location.

[shadow.realm]

Sorry, it is round.  The dimensions are added into the PDF manually.  How do I put the dimension lines at targets spots when there is nothing 'to target'?

[jhackney1972]

I would probably dimension this component using a Section at the required height from the base.  I have attached the model so you can see how I created a sketch line at this height, made it visible in the drawing, and then used this to create my section line location.  I did not attach the drawing, you can practice that for yourself.  There are a few other ways to dimension this component, which you did not supply, next time do that, but all should define to the machinist the critical dimensions he needs for fabrication.

By the way, in your provided PDF illustration, you placed a rectangle box around the 1.00 dimension.  Do you know what that means?  That is a Basic dimension and you are asking the machinist to how this dimension as precisely as possible.  When you ask for such high tolerance, you are increasing the cost of the component very quickly.

[Anonymous]

Thank you for the reply.  In the case of the 'basic', it is just that.  The meaning on all the drawings I have seen/used that have this requirement means:

At the 2.000 dia. exactly, measure the distance of the 1.100" ±.005.  I have seen and machined parts both round and flat where the dimension at the 'length' is called out to a specific 'basic' callout on angles and radius.