[quote=leeboweffect][quote=Dogboy]You're kidding, right?[/quote]
No, not kidding. You will crush/deform the tube slightly if you're center punching it. This is just thin wall 6061 aluminum tubing, not boiler plate.
[quote=Dogboy]I center punch aluminum (plate, tubing, whatever) all the time before drilling and it works just fine (as does the very seasoned machinist at our plant). This is SOP for drilling holes in metal.[/quote]
For hand work (accuracy +- 0.010") OK on plate and/or flat stock, but NEVER on round stock. A "seasoned" machinist would never use a center punch (very cave man way to do it) to locate a hole on round stock as it would end up way off center unless dumb luck is on your side. The v block I suggested above is the best way I've found to do it accurately with hand drill. If you have machine tools here are a couple of unsophisticated ways to do it:
[url]https://www.youtube.com/watch?v=eUTWtHOVyPI[/url]
[url]https://www.youtube.com/watch?v=JRJOtQNV8RU[/url]
A machinist with a complete shop would not use any of the methods above if maintaining the center line is critical which it is on these parts. Old school would use a vertical mill with dial indicators on magnetic bases, moving in to the late 1970's would be a vertical mill with digital units and most current a CNC.[/quote]
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