Hole pattern - ideas needed

tcweb

tcweb

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I need to take a 10.5" piece of round sheet metal (any thickness will likely be OK) and drill as many 1/2" holes in it as possible. It's going to be a sifter/sorter.
I figured I'd make a quick fixture of a sacrificial piece of aluminum or wood and use some small screws to hold the sheet metal in place.

After that...not sure what to do. I was thinking using a rotary table on a mill. Use a 1/2" end mill and set a depth stop to the thickness of my sheet metal.

I do have access to a CNC (2 axis) mill, so maybe writing a program would take the brain work out of it?

Any ideas? prototype doesn't have to be perfect, but I'm guessing I"m looking at drilling several hundred holes (too lazy to do the math right now!)

-Tom
 
Gcode generator for holes on a rectangular grid. (Have not tried it.)
http://www.intuwiz.com/drill-rect-grid-points.html#.XgUFbFVKiZQ

Edit: Possibly, you could generate two arrays at 2X the desired center to center distance from each other and offset the arrays 50% from each other. That may be a more dense set of holes. In either case, you can then just remove the undesired center points from the gcode to form a sort-of circular pattern.
 
As far as the tool, an endmill is not the correct tool to use, they don't really like to drill holes. A step drill would be my weapon of choice for sheet metal.
 
Agreed. My dilmena is holding the workpiece down. I figured screwing it to a sacrificial piece of plywood would be easiest. And although an endmill is not ideal, I was thinking that since it's only 16-18ga metal, it would be OK. it would at least NOT need clearance under the part, unlike a step drill.

I may get through 3-4 holes and need to re-think that, I realize.
 
tcweb said:
Agreed. My dilmena is holding the workpiece down. I figured screwing it to a sacrificial piece of plywood would be easiest. And although an endmill is not ideal, I was thinking that since it's only 16-18ga metal, it would be OK. it would at least NOT need clearance under the part, unlike a step drill.

I may get through 3-4 holes and need to re-think that, I realize.
Click to expand...

I would just stack up enough plywood to clear the step drill. MDF is normally my choice for a spoil board, but plywood works fine.

Also, if you have access to a CNC mill, that would be my first choice. Would make life a lot easier and save your arm.
 
I think if you make a punch for it, would be a quick work. Design the circles on paper and print them out. Glue them as needed.
Then cut and glue the paper onto the sheet metal and keep punching.

On the punch, I wouldn't worry too much about doing it right with the sifter. But if you have something like 10 holes, maybe faster with drill.

You can also get away using the fastest method by making the punch, and put it on a hard piece of wood, like oak or something and hammer it away, not even need an alignment tool and the bottom die.
 
Having access to a CNC mill, that is the way I would go. Much easier than trying to manually locate each hole. I would make a pilot hole for each hole and rerun the program for your final size. I would think the end mill would work if you have a pilot hole. Drilling holes in sheet metal isw problematic, especially if they are closely spaced. The end mill would be less likely to grab and deform or tear the sheet.

I did a similar project when I more than tripled the number of holes on my coolant screen. 216 additional holes. The CNC G code program made easy work of it.
 
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