When drilling on the mill I just prick-punch and then center drill.Guys here's the rest of the problem, even if you get it punched dead center of your scribed lines then you need to line it up on the mill which unlike a drill press which is sloppy enough that it will find center on its own a mill is rigid enough to drill off center of the punched hole. Trying to line up to a punch mark that is now .050 wide is problematic. I had been bringing a small drill bit down, observing its deflection in the punched hole and adjusting but even that was not fool proof and kind of a pain.
Once the DRO is on the new mill this whole thing becomes moot of course.
.....unlike a drill press which is sloppy enough that it will find center on its own a mill is rigid enough to drill off center of the punched hole.
I added a camera to mine, makes it a lot easier to see with my old eyes and stiff neck.Another way to accurately locate position on a mill is to use an optical center finder. They have a 45X magnifier and are capable of locating a position to .001".
If you are referring to the type that has a optical round piece with cross-hairs and a short transfer punch? No, I wanted one. What I have is a optical piece what looks like small magnifying glass that I used check my punch mark location afterwards. It has crosshair and othe markings. I have had it for about 40 years.Has anybody used one of those optical center punches?? Always thought I might get one to try out.
My Starrett spring loaded punches seem to work quite well. I first hit the mark with one of the little ones, followed by re-punching with a larger one.
I can't claim to run a high precision shop, but I usually hit the mark within a couple of thou.
Chuck the grumpy old guy
Well show me a spring loaded center punch that's not China these days but I spent $30 on the last one at our huge local hardware store.
The methods described in posts 10, 14, and 17 above will work. For accuracy, the optical center finder will get you within a thousandth or two. Allowing the drill to find the center of a punch mark on a loose workpiece is fairly good. I will sometime put a small sharp point in a collet and visually line a workpiece up in the x and y directions.The sharp point is better at eyeballing the center than a drill. When I have to relocate an existing hole, I often put a matching pin in a collet and run the pin into the hole in the workpiece. It will automatically center the hole in the direction parallel to the vise jaws and the vise can slowly be closed while observing movement of the part, The axis perpendicular to the jaws are adjusted to just bring the part into contact with the fixed jaw.This is a newb question for sure, but perhaps this is the place to ask it.
How are you guys locating on your punch dimple once the piece is on the mill table? I can get pretty close by using a punch then 'eyeballing' with my spotting drills, but there has to be an objective approach to locate over the dimple.
Is that what the conical 'finders' are for? Anyone have a link to a video showing how they work?