Corner rounding tools

[photomankc]

Is there any standard to the geometry on a corner rounding tool? I have a tool that is a 1/8" radius with a 5/8" large diameter and 1/2" shank. I think the small diameter is 1/4". Is there a way to know just exactly where set the tool in offset and depth to get the radius centered where it needs to be? I looked around but didn't find anything like a general formula or anything.

[Delw]

Use a optical comparator and check them. thats what I do. or use calipers and get them close
I found when using cheap courner rounding tools you will never get the same z- dim and most of the times the x is different by a few thousanths.

I buy them in lots of 4 and they vary in the lot as well by as much as .010.
the carbide ones are pretty much dead on every time.

[Geof]

Not having an optical comparator (other than the pair in my head) I stick a piece of scrap in the vise and calibrate them by trial and error.

[photomankc]

Ugh, I was afraid you guys were going to say that. Going to have to play around a bit then I guess. I was hoping for some cool formula that they all tend to use but I can see how the variance being that big rules that out.

My optical comparator has not yet been left under the Christmas tree!

[mfgbydesign]

Program the diameter for the nominal size where the radius becomes tangent with the tip. Add .010" to the diameter comp.
Touch off the surface tangent to the radius. Add .010" to the length offset.
Now run the cutter, and adjust the comps little by little until you get it dialed in.

[fizzissist]

Another trick (which I never use since I've got an optical comparator) to use if you can't actually do test cuts is the old paper trick.

Bring the tool down in Z and slowly slip the paper back and forth on top of the material, and add the thickness to your Z offset. Do the same for the side for your diameter offset.

It won't be perfect, but it's quick to getting you dialed in.

Just like all guns are always loaded...all corner rounding cutters are always different, so you have to check each one.

[photomankc]

Thanks for all the tips! I better test on some scrap before I go and try to do it on the Christmas gift I'm working on.