Gratuitous swarf photos

I should have mentioned that - I'd always been told you _must_ use a spiral fluted tap, otherwise there's a portion of the tap's rotation when nothing is touching and the blank can rotate out of step.

Jeff,

In my experience, the spiral-fluted taps are more expensive than spiral-pointed taps and thus less common.

You're right though. Very common in CNC applications and certainly widely available in North America.

Regards,

Robin

And it's my experience that the spiral flute taps aren't as strong and don't cut as well as spiral point taps. I know I was real unhappy with the amount of flex I got with 1/2NC spiral flute taps when tapping SS. I was sure that I was going to break a tap. In the same situation a spiral point tap is a walk in the park.

On the other hand spiral flute taps will curl the chips out of the hole nicely. But after the above experience I won't use any unless I'm forced to do a bunch of blind holes that don't have room for drilling deeper for chip clearance (fortunately not something I run across very often).

Wayne Cook Shamrock, TX

Now I'm feeling silly. I'm not at all familiar with spiral pointed taps - just plain straight ones, and spiral fluted ones. Thanks for the info, gents

-- Jeff R.

You are absolutely correct. The spiral fluted taps are weaker. Also, because the chips are directed back out of the hole they drag on the way out. Depending on the material this can damage the thread, break the tap, or both. If the material is ductile enough I like form taps as a first choice. Especially for blind holes. If the material can't be form tapped and has a through hole the spiral point tap is my first choice. Only when forced will I use the spiral flute taps. ERS

Amen!

Wayne Cook Shamrock, TX