Here ya go. Old timers trick you won't see in a machinist's handbook. I knew it a long time ago and forgot it until I just found info on it. Copied and printed it to keep in my shop info. If ya don't understand it just say so and I'll try and explain more.
Works great on Bridgeport mills or other manual mill with a movable/tiltable head. When you have an Endmill of a known diameter, and you need a large diameter radius cut into a piece of material than the diameter of the Endmill is.
Divide the cutter diameter by the “diameter” wanted, the result is equal to the Sine of the angle that the mill head shall be tilted from vertical to cut the larger radius with the end of the endmill.
In other words, if you have a piece of flat material and you want a 3/4" wide x 10' diameter, shallow radius slot cut into it, you can use a standard straight square ended end mill LARGER then the width of the slot so say a 1" endmill, but tilt the mill head to the correct angle and the bottom of the end mill will now cut a spicific radius in the material LARGER then the endmill is.
RADIUS CUTTING FORMULA FOR MANUAL MILLS.
Works great on Bridgeport mills or other manual mill with a movable/tiltable head. When you have an Endmill of a known diameter, and you need a large diameter radius cut into a piece of material than the diameter of the Endmill is.
Divide the cutter diameter by the “diameter” wanted, the result is equal to the Sine of the angle that the mill head shall be tilted from vertical to cut the larger radius with the end of the endmill.
In other words, if you have a piece of flat material and you want a 3/4" wide x 10' diameter, shallow radius slot cut into it, you can use a standard straight square ended end mill LARGER then the width of the slot so say a 1" endmill, but tilt the mill head to the correct angle and the bottom of the end mill will now cut a spicific radius in the material LARGER then the endmill is.
