Drop Out

No I don't mean that overpriced graphite spray from Frankford Arsenal.
No I am not taking about the horrible realization you get when you discover
you have been pushing a weld bead just a little bit to long on some aluminum sheet.
On lots of videos you see guys machining sheet or flat bar where they just cut a profile and the part or waste piece just drops out pretty as you please. How the hell do you do that?
Every time I try atleast a couple times during the job I'll get to hear the piece bind on the mill or bang off the inside of the mill enclosure. If I really need to do that I'll use the super glue and masking tape method to secure the whole work piece. Then unless the pieces are very small they just sit there without moving.
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On Mon, 26 Nov 2018 11:35:57 -0700, Bob La Londe wrote:

WHAT? An on topic post? What's WRONG with you!
Well, I think it has something to do with the Z plunge you make on each pass around the material. If you are cutting all the way through the material in one pass, there is a lot of side-force applied to the blank that is supposed to drop out. If there is enough side force, it can break the cutter, or leave divots in the workpiece.
I make a lot of instrument panels with cutouts that are supposed to drop through on the last roughing pass. Haven't broken a cutter in some time.
Jon
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On Mon, 26 Nov 2018 16:54:01 -0600, Jon Elson wrote:

...

...

One could try leaving thin tabs or bridges, on opposite sides of the part to be dropped out, to be cut last. In the waste area cut a wider path above the bridges, wide enough that as or if the part swings down it will clear the cutter. Once all but the bridges have been cut, cut them at the fixed ends, away from the dropping part.
--
jiw

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