arc tangent to two other arcs

[powerfulp]

Ok, I know this is basic basic stuff but I've been messing around trying to get this for too long and I need to program something real quick here so I had to come get some help.

 

All I have is two circles (125mm dia) ,they are next to each other (centerlines are 140mm apart in X; they are on the same Y plane). I need to make an arc tangent to these two arcs, at the top. Please if someone could give me a step-by-step on how to get this done, it would be much appreciated. I've tried a lot of ways and they are just not working. What do I need to define, etc etc etc

 

Thanks!

[Joseph]

Fillet with no trim is quick and easy

[LA CAMmer]

Create/Arc/Tangent/2 Entities then enter a radius and pick the two circles.

[jeff]

create/arc/tangent 2 entities, enter in your arc radius, then click on the 125mm arcs at the 2 o'clock (left arc) and the 10 o'clock (right arc) position (approximately)

Is this what you're looking for?

[powerfulp]

I don't know the radius between the circles. So is this even possible? Seems I would need more information...

[Pilot Plant Supervisor]

Maybe I'm missing something? Just draw the two circles, then create-arc-arc tangent, click the two entities button (icon looks like fillet), then click each circle at the top.

[Colin Gilchrist]

If you are using Create > Arc > Tangent, you need to enter a radius first, before selecting the entities. If the initial radius value is too small to fit an arc between the two circles, the function will fail...

 

The question you must answer is: what radius do you want to use for this tangent circle? Try using 150 mm, and see if that at least will create the arc you are looking for. If you have a large radius like that, Mastercam will present you with many possible tangent arcs (shown in yellow, with default shown as yellow dashed entity). You need to click on the tangent arc you want to use. It will now be shown in blue and is a "live" entity. So if you don't like the size, you can enter a new radius and it will re-create the tangent arc...

[LaszloK]

You need one more argument in order to get a solution. There are infinite possible radii that could be tangent to those circles. Is there a passing through point or another tangency condition you could use?

[MotorCityMinion]

Go old school. What size radius is the third arc? This is critical as quite a few sizes will fit in there tangent to both arcs. Add that number to the radius of the existing arcs, then make 2 concentric circles of that size (at same centers as arc 1 and arc 2). Where the two circles intersect will be the center of the 3rd arc. This works even if the first 2 arcs have different rads.

 

If you don't know the value of the 3rd radius, just make something up and change it until you get satisfactory results. Good practice either way for more serious curvature work down the road.

 

Anybody got a compass?

 

Mathamajical vernacular aside, I just noticed that LaszloK said something similar.