I'm Sick Of Spring Loaded Center Punches

[coolidge]

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.

 

[coolidge]

Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

View attachment 253356

 

[John Hasler]

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.

When drilling on the mill I just prick-punch and then center drill.

 

[JimDawson]

.....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.

One trick that I use in the mill is to leave the work a little loose in the vice or on the table. That way it emulates a drill press and the center drill will find the center of the punch mark. Just make sure the work can't get away from you.

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".

I added a camera to mine, makes it a lot easier to see with my old eyes and stiff neck.
http://www.hobby-machinist.com/threads/microscope-camera.35888/
.
.

 

[mattthemuppet2]

if you're careful you can lightly touch the spinning drill l to the punch mark and see if the ring of cut metal is the same width all around the punch mark. i usually do that after lining the flutes up with the hole. tbh, i think stub drills would get me better accuracy - the amount that even decent standard length drills can walk probably outweighs any effort i make at accurately locating it

 

[RJSakowski]

It's the fact that drills walk that allow you to hit the center punch. I used to drill thousands of holes in printed circuit boards using #72 carbide drills. The drill would orbit around the center punch before settling on the center. The home made drill press had enough play in it that it would accommodate the offset and drill the hole without breaking the carbide bit.

As long as the point of the drill is inside the center punch and the work is free to move relative to the drill, you should be OK.

 

[mattthemuppet2]

that last caveat is the key..

 

[gjmontll]

Above, Chuck mentioned the optical center punch. I've used LMS's optical center punch for several years. It works quite well, even for my elderly eyes.

http://littlemachineshop.com/products/product_view.php?ProductID=3186&category=

But it does have some drawbacks:
Getting enough illumination when you are bend over it looking into the lens, you're probably casting a shadow over it. Without direct light, the image can be rather dim.
On small/short/narrow pieces, it can be tough or impossible to achieve an adequately steady footing for the base, which is 1.875" in diameter. And any hole within 0.938" of an inside corner is unreachable.(Perhaps you can make your scribe marks on the other side of the material - not always an option)
If you have a bunch of spots to mark, it is a bit tedious, as in: position the base over the scribe marks, insert the lens, look thru the lens and precisely align it, pull out the lens and set it aside (I hold it in my teeth), insert the punch, pick up the hammer, tap the punch, put down the hammer, pull the punch, swap the lens back into position, and go to next spot ...

Greg

 

[george wilson]

I was silly enough to buy one of those laser center finders. Forget it! The dot it projects is way too large for accurate work. I can use it when drilling jewelry models(for subsequent casting),but that's about it. I am not sure of the diameter of the dot it projects. .015"? Whatever it is,it's way too large for precise centering.

 

[kd4gij]

First it sounds like you have been using harbor freight class spring loaded center punches. That said I have been known to use starter taps that have a nice point on the end to locate layout points.