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This topic contains 14 replies, has 4 voices, and was last updated by  Jim 2 years, 9 months ago.

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  • #15416

    Jim
    Participant

    I’m a little frustrated because I can’t find a way to create an arc tangent to 2 entities. Fillet won’t work because the arc is larger than the distance the geometry shows. But by two points it would work fine. Something this simple should be included in the Arcs menu. Anyone?

    #15559

    Mike
    Participant

    Could you attach the file your working with so we can take a look at what isn’t working?

    #15560

    Jim
    Participant

    ok. I think this show my situation.

    #15561

    Jim
    Participant

    Hmm. How bout this?

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    #15565

    Mike
    Participant

    What BobCAD will do when you create a Fillet is pretty much follow each line down .625 and then it will draw an arc that fits between those two points.

    What you will need to do is extend the .5 in line to a length over .625. Then you can trim the to where it meets the your line on the angle. See the attached pictures and let me know if that is what you are looking for. Is is just not possible for the software to fit an arc where there just isn’t room for it to fit. You can figure out where the Midpoint needs to be and then use something like a Blended Spline.

    Take a look an let me know how it looks to you.

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    #15567

    Mike
    Participant

    Also see the attached picture here and you will see even if you set the line up correctly then that half inch point is just a little bit away from that line. That is the issue you will run into is that the angle line you had wont touch the line at the correct point.

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    #15572

    Jim
    Participant

    Your first shot of the standard fillet is understood. But that’s not my issue. And in the second shot, the arc still isn’t tangent, and it could be with a “tangent to two points” option in the Arcs menu. Those two points could be points, endpoints, midpoints, an arc, etc. The arc is still of a bit in X.

    I guess what I mean is that there should not have to be sufficient length on either end to create arc.

    Here’s a more simple example maybe:

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    #15574

    jrmach
    Participant

    Figure out your chord height.Put a point at that height between your 2 other points.Then do a 3 entity arc.Yes you got to do some basic math to find chord height.

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    #15576

    jrmach
    Participant

    I incorrectly called it chord height,,here in this link they call it segment.Anyhow this link will make it easy for you to find the third point needed to do the 3 arc entity.

    http://www.1728.org/circsect.htm

    #15584

    Jim
    Participant

    Your screen shot doesn’t really apply. What if, as in my example, the two endpoints aren’t equal in Y? Or, as previously noted, tangent to an endpoint and another arc? Good luck with that. “Tangent to Two Entities” is a basic command that needs to be added. Badly.

    • This reply was modified 2 years, 11 months ago by  Jim.
    #15588

    jrmach
    Participant

    As I have only used BoB ,none others,I have no idea if the command can/or does exist in other software.
    I do know between my BoB skills and my math skills I can do whatever is geometrically possible.
    I can suggest you put in a feature request for this said 2 entity tangent.
    If there is a particular drawing you are having a problem with,I would be glad to show what work flow I would do.Maybe not a one click solution,but will git er done.
    BTW,the 3 entity arc works with lines,other arcs,and points,,any combination.
    A down and dirty solution is to create an arc and zoom way in and do a translate/drag.

    #15589

    jrmach
    Participant

    Oh and to answer your question
    “What if, as in my example, the two endpoints aren’t equal in Y? Or, as previously noted, tangent to an endpoint and another arc? ”
    Give me an example.If it is geometrical possible,one would not even need CAD,,,just Math…..

    #16409

    Jim
    Participant

    Surfcam, Mastercam, GeoPath, even G-Zero will all perform this operation. Here’s another screen shot showing what I’d like. Came across this today. The large circle (arc) is .5 radius. The smaller rads are .030 at the end of a .250 rad arc. This is a simple example, but still applicable. I want the circle tangent to the .030 arcs.

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    #16434

    Shane
    Participant

    Hi Jim. I don’t know if this will help or if you’ve already figured it out, but BobCad won’t do it, but I learned to cheat. By your first example, all I do is choose fillet and put a tiny radius on the angle intersecting the 90 degree leg, like .001 or .002, then the function will work. Choose fillet now and it will work from that tiny radius to the bottom. You have to zoom way in to grab it, but it works. Again, it is cheating and hopefully you can get away with it if the sharp corner isn’t a big deal. Let me know if that works for you.

    #16654

    Jim
    Participant

    Yes. Good enough for me. Thank you!

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