Radius tool setup??

Can someone please explain how to set-up an edge radiusing tool. My problem is I don't know how deep and how far in to set the cutter. There is probably some thing simple I'm over looking. Here is an example of my problem. I have a cutter that is labeled ".015 rake 1/8 r". I would like to radius a 90 deg edge to a full 1/8th inch. With out a large amount to trial and ERROR how deep of a cut would I have to make and how far in. Down .125 and over .125 would make sense but this will not work with the tool I have. I mounted a piece of scrap 6061. I set my dro Y 0 to the edge of the stock. I set my tool up for Z 0 with the tip of the tool resting on the top of the stock. I then relocated Y and Z to -.125". After a test cut I barely touched the part edge. I bought out a small shop a few years back. With it I received a large number of endmills, some of them radiusing style. I can only assume they are standard cutters. They don't appear to be regrinds.
Brian
Thanks Brian

"Hshop" wrote in message ...
  Quoted Text Here  
Hi Brian;
I suggest that you post to the group "rec.crafts.metalworking" which is very active and full of very knowledgeable metal workers...
Your description is confusing.
I assume that you want to cut a 1/8 radius along the edge (along the X-axis) of a square or rectangle piece of metal with a milling machine. I assume that it is a convex radius (rounded edge) as opposed to a concave radius (leaving two sharp edges - one at top edge and one at side edge).
The label on the tool does not necessarily mean what you think it does; probably but not always. This may be an end-mill meant to cut a vertical face on the work, for 1/64 th of an inch or a 1/2 inch, before beginning the radius cut of 1/8 r. Same for the outside diameter of the endmill... It may cut "flat" for an additional amount after the radius cut (in the y-axis direction).
You stated that you do not know the origin of the tool or whether it is "re-ground" so I cannot tell. It may even be a "special order" tool designed to cut exactly ten thousandths (for a step) along the X-axis (into the Y-axis direction). Remember that the label of 1/4 R. only describes the radius on the tool - not the length or outside diameter... sometimes but not always...
You may want to buy some Radius Gauges (expensive but useful); otherwise examine the end-mill first. Put (stand) the cutter on a surface plate or any reliable flat surface on top of a 1/8 thick flat and slide (roll it on the plate) a 1/4 inch drill blank or other reliable 1/4 diameter round stock into the curve of the radius. Now hold something white behind it and sight how it fits the tool radius... Do the same with when the tool is on its side (much harder because the flutes curve - may need a "V-block" on the shaft for this)
In short - it is never "safe" measure in the manner you describe - from the outside edges "into" the radius unless you "know" the actual distances on the tool... ;-}
I also do not understand your objection to "trial and error." It sounds as if you are attempting to cut the "entire full depth" of the radius in a single pass. If you are doing one piece (or just a few) do it in several passes, raising the work a (few thousandths) into the cutter and feeding it into the cutter and "sight it" after each pass for the "blend" to the vertical and flat surfaces. Do this with an "extra" and actually start cuttin the flat surfaces, then back off for the correct reading...
When you have found the radius you want on the work, reset the dials to zero, and repeat for the few that you want. Remember that you want to be cutting along the "locator edge" of the piece being held, not on the opposite side which will allow errors of exact width to vary the depth of cut.
If you are actually setting up for "production run," by hand (or on a CNC machine), you must make sure that your tool is a "standard" so that you can order or have another on hand in case you need to change it at some point in mid-run.
Yes, the process could be calculated, but even on a CNC (if you are doing the programming) it is easier and faster set-up (read cheaper) to take the readings from the dials at the finish of the previous operation, keep track of these measurements and movements, take the final readings from the dials when finished, and then program those movements.
JHbs