Power Tapping on a PM25?

devils4ever

devils4ever

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As you can all see, I'm making a tool plate to help hold parts while CNC milling. I drilled a 1" grid of holes that need to be tapped 1/4"-20. All 58 of them. I did two by hand and decided I need to power tap. Can a PM25 mill do power tapping? I know there are tapping heads, but they are $$$ and take a lot of vertical space.

Can I chuck the tap in the keyless chuck? Should I get a spiral tap? All I have now is a 4-flute straight tap.

20200419_170858_edit1.jpg
 
By all means, use a spiral point tap, or expect broken taps, when I power tap, I tighten the drill chuck enough to allow slippage if something goes wrong.
 
Spiral point tap or spiral flute tap?
 
devils4ever said:
3/4" through hole in 6061.
Click to expand...

My guess is that IF you had already power tapped lots of holes, you will be fine power tapping 3/4" in 6061.
My additional guess is that you fail the sentence above, and thereby, you should expect several broken taps if you attempt to power tap said holes.

I power tap 1/4-20 all the time in 1/4" 6061, but anything thicker, I let the mill start the tap (i.e., straight) and then I finish by hand.
 
From my email, I can see there were more responses to this thread that aren't here because of the server migration. If you posted here and don't see it, please re-post. I think I lost some valuable information.

Thanks!
 
You can make it easier by drilling the holes slightly over size of the ideal drill/tap size. There are charts that show how much over size and what percent decrease in thread strength.

With that length of thread you could lose 20 percent thread strength and not notice any effect on function but get a much easier time of tapping.
 
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