Problem Snapping To Tangent

Hi,

ACAD 2008, I`m Having all sorts of problems trying to draw an arc joined to a circle. I have got it to work once but can`t seem to do it again. Is it possible I have something active which is stopping the snap to Tan. Everytime I try it, the snap seems to be in a different position.

Do you use Lines or Polylines? with Polylines you can draw a arc within the command - read the command line!

second - the tangent-snap - turn it off in the OSNAP settings box?

Unfortunately the way the Tangent snap works is it draws a direct tangen from the last point selected... in a straight line... but you're trying to join something that's not straight & not yet properly defined (unless you already defined it's radius in which case the exercise is fairly pointless). Your best route forward is to create the arc using construction lines & a circle.

Thanks for the prompt replies but not solving problem. I`m concerned I may have something active because I`ve managed to do this before.

I have attached file for your perusal, see what you think.

problem.dwg

ah sorry...I didn't read the question - thought it was a straight line and a arc...Pline won't work for circle and arc ..sorry

Similar has been covered quite recently as far as a work around is concerned- you can draw a line out from the centre of the circle and use the intersection as a tangent point- so long as you're snapping a mid- or endpoint of the arc, otherwise the tangent point of the arc would need to be calculated as well, again you can use a line from the centre to give the required tangent.

Edit... The last bit above can be ignored- if you draw a line in the circle this can just be copied/ pasted into the arc centre, then extended. Sorry but it is Monday

Thanks again guys but can`t draw line out as there are no sizes to work to. But anyhow I have drawn this correctly before with no prob snapping to tangent . decided to try it again as a practice for an exam i`ve got on thursday and cant seem to get the right tangent snap. Thought something was active that may be stopping it but will have to keep trying. thing is if you try it the tan osnap is in different place each time you try and draw the arc.

It's possible to have it look like it worked, but by accident... if the last point you've chosen happens to be at the correct angle for the tangent to work then it'll look correct but it's pure coincidence & is unlikely to stand up to close scrutiny.

by using the ARC command; pick start point (lower edge in dwg) then; enter E for end pt snap with tan on circle; enter R for radius and enter 30. Seemed to work fine; not sure if this is what you wanted??? can convert to pline then.

problem[1]_2.dwg

Are you trying to get the concave or convex arc?

See if this is what you need.

I usually find it easier to draw a circle, then trim to get the arc.

You can find the center of desired 30R circle by drawing 2 temporary circles. Offset the 20R circle by 30 (since tangent, its center will be on this offset circle). Draw other 30R circle centered on the corner where the arc is to intersect. The intersection of these 2 circles will be the center of desired arc.

Thanks for the effort Beammeup but no, I need the arc the opposite way around. See attached, This is the one I drew a while ago but as I have an exam coming I thought i`d do it again to refresh my memory. Lost all confidence now though. Thanks again.

2DPA01TEST-LEV2.dwg

Eldon, that`s what I want, how did you do it. Slw 210 that`s right too but I know I did it by snapping to tan.

samson,

The drawing you attached does not have the arc drawn accurately, it's not tangent to the upper circle/arc. You can see by drawing a line from center to center of the arcs, line doesn't pass through the point of reverse curvature. I don't think you can do it "snapping to tangents" as there is only one tangent available.

CarlB, You are right about about arc being drawn wrong and your solution works perfectly. Thank you.

You're welcome, glad to help. SLW210's method also works, although mine follows (my) thought process.

Eldon, that`s what I want, how did you do it. Slw 210 that`s right too but I know I did it by snapping to tan.

Now my router is up and running, I am back on line, but it all seems to have been sorted.

I did it exactly as CarlB described. I tried snapping to tangents, but thus is a case where that technique just does not work, and geometrical construction is the sure fire way of accuracy.

Thanks to all who posted. I am learning so much from this board.