Line tangent to specific point on circle

[BillW435]

Hello all -

My question: How do I draw a line line tangent to specific point on circle?

I have a point on a circle. Need to draw a line through that point and tangent to the circle. I can think of work arounds, but there must be a simple way.

Appreciate any help.

Thanks

Bill

[steven-g · Accepted solution]

I don't think there is an option to draw from a snap point (only to a snap point) I would draw from the point to the centre of the circle then rotate the line 90° and extend/trim, or set the UCS to the center of the circle and X on the point then draw with ortho on, but thats work arounds. I'll be interested to see what other options people come up with.

[BillW435 · Accepted solution]

Thank you very much Steven!  I had experimented with "work arounds" to accomplish my ojective. Your solution is best; I will quit trying to use the tangent snap, it seemed there was no way.

Have not heard from you since we communicated about auxilliary views and wood staves. I'm still doing staves in woodworking, but now turning the staved vessels on a lathe.

Hope all is well with you.

Bill Wells

Olympia WA

[steven-g]

Hi Bill,

Happy to help, glad to hear you are still keeping busy

[hwalker]

Another workaround would be to draw a line from the centre of the circle to the point on the edge of the circle and then draw a line from that point to the external point (if you get what I'm talking about. I don't :D)

[steven-g]

If the external point was Tangential, why would you need to draw from the center of the circle first, if it wasn't then it wouldn't, would it, or would it.

[BillW435]

Thanks H.

But there is not an external point.  There is just the point on the circle. I'm drawing a line both through the point and tangent to the circle at that point.

While you are all here, what is the *best* way to draw a line at 90 degrees to another line, at a specific point on that line? I can do this, but then I think "those guys at Autodesk Community could do it so much better".

Bill

[steven-g · Accepted solution]

It's the same problem again, Autocad alignment snaps are designed to go to an object not for starting points (well at least not in the way you are trying ) , the only way I can think of is draw a line and rotate it afterwards by 90 degrees or change the UCS to align with an object and then use ORTHO. Depending on what you are doing ie. is it regular you might be able to have a macro setup to do something like that, but how it works would depend on what you intend doing. If you can give an idea of how you use this I could possibly give you more help.

[BillW435]

Steven, the circle is the 8" wheel of a grinder I am using for woodworking tool sharpening. I am messing around with the angles used for chisels and turning tools. So, if I know the angle formed between the tool and a line tangent to the wheel, at the point of contact, then I know the bevel being ground on the end of the chisel, say 35 degrees.

I'm trying to design a better sharpening jig for use on a grinding wheel.  I have all the AutoCad information I need for now, but since you are a woodworker, I may share my design with you for your comments. It will not be soon, however.

I will use your suggestion to draw a line and rotate it afterwards by 90 degrees. I had been drawing a new line perpendicular to the first (using perpendicular snap), then moving that line to end of first line.

Thank you again.

Bill

[steven-g]

Bill, I look forward to seeing the design. I just had a thought, I don't know if you are aware of grip editing, it's second nature for me, but if you draw a line from your starting point on the circle to the center of the circle. you don't need to use the rotate command to make the changes, I'm not sure in which version it was introduced, or which version you use. But if you click on the line and highlight it, then click on the grip at the end of the line touching the circle, if you now press the spacebar Autocad will let you do a number of things with the line, you can either stretch it move it rotate it scale it or mirror it, you might use this already but if you don't I'll bet you go WOW, you need to press the spacebar each time to cycle through the different options (keep on pressing and it will go through all 5 options then back again) it is a great time saver, and using the Ctrl key as well you can lengthen the line or copy it.

Different objects can be altered in various ways.

[BillW435]

Thanks Steven, I just learned something very useful! It worked for me, I had not known about it.

I use ACad LT 2011.

Bill

[gadavis57]

I had the same problem tonight and that is what brought me to this forum.  Imagine the euphoria combined with a moment of stupidity when I realized that a radius through a point will always be 90 degrees to the curve. At that point it is a simple matter to draw the tangent line 90 degrees from the radius. That is indeed the best method...... and I spent a half hour trying to figure out how to draw a line normal (90 degrees from) a curve at any point, knowing that if I could that, then I could construct the tangent line. 

Thank you all so much.  

G. Davis

[BillW435]

Thank you again, Steven. Gee, it has been six years...

Bill