Workholding suggestions?

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I have some plywood that I need to cut multiple holes in, see image below.

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Each hole is about 1 inch in diameter. The plywood sheet will be held down with screws to the spoilboard. My concern is cutting out the holes and the remaining disc (I’ll call them “coins”) that is left after cutting the holes. At this time, I’m thinking 1/4" or 1/8" endmill to cut the holes but I’m open to suggestions on that as well. Tabs are not really an option based upon size and (lack of) ease cutting them loose.

A couple of thoughts (open to ALL others!):

  • Put painters tape/masking across the bottom of the entire sheet of plywood to hold the coins as the final (upcut) pass is cut (multiple sheets! A LOT of tape!)
  • Use a 1/2" or larger endmill so there is no coin left after machining the hole

Your thoughts, folks?

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Assuming the plywood would be a nominal 3/4" thick and flat, I would simply use tape and cut with a 1/4" compression bit.

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Use a 1/4" end mill and use a pocket cut operation. This will clear the hole out as sawdust, so you don’t have to worry about the remaining discs.

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Grind them into dust.

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You could use a pocket to eliminate the material, use tabs and remove all the blanks after, or use the blue tape method (or double sided tape) to hold them in place after they “break free” from the material.

-Tom

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Mike,
If you haven’t tried it, an amazing feature of an 1/8 inch compression bit is that it fills the cut with sawdust to a level that no cut out article will move in the cut. I have stopped using tabs on profile cuts because of this situation.

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I tried that today. Unfortunately each of the “coins” popped loose…

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With only 1" holes I would recommend a pocket operation as well. More than half the material is gone after running the 1/4" bit.

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I agree with the recommended pocket ops here give the small diameter.

Another option for larger interior thru holes/openings is to drill 2+ holes on the interior of the opening, shoot screws into them, and then just profile the opening along the interior edge. The remaining stock on the interior of the part will be held down by the interior screws. When I do this, I often place the holes in the CAD model and export a quick program to make the holes with the machine. This quick program makes sure I’m using screws in the right spots and won’t blast through them. I most often use this technique for tight nests where material yield is of critical concern and I’m trying to get the most parts out of a sheet of material as possible (i.e. composite sheet stock).

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