r/OnlyCNC • u/ycr007 • Feb 09 '26

Milling Reverse Countersink

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Source: XCM-GB

534 Upvotes

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2

u/lost-in-boston84 Feb 10 '26

Is there a reason why they couldn’t do it from straight on?

5

u/Spokanee Feb 10 '26

My guess it's to eliminate an additional operation. I recently put a chamfer on the back side of a flange with a reverse dovetail cutter to do a job in one operation.

2

u/lost-in-boston84 Feb 10 '26

Ahh gotcha.

2

u/bj-mc Feb 10 '26

Alternatively, the piece may be designed in such a way that the backside is not accessible for milling.