Deep Hole Tapping

[JR49]

better than the three tap set is to use a gun tap also known as a spiral fluted tap a much better tap great for thru holes the chip flows out the open hole and clears itself

I agree with what you said bfd, except for the name . You referred to the gun tap as a spiral flute tap , it is actually a SPIRAL POINT TAP that pushes the chips ahead, and out the through hole. The spiral flute tap pulls the chips up and out of the hole much like a drill bit. Hope I explained this OK, JR49

 

[Tony Wells]

You did, JR. I want to add something to the spiral flute tap description though. When you are running them in, they sort of "unwind" and get a little larger due to the torque. Then when you back them out, they relax and are smaller and so come out with less drag on the edges. It's not much, but enough to help them last longer. They also work much better in a machine and all in one shot.

 

[bfd]

jr you are right I don't pay much attention to names of items. many items are known by different names in different areas(shops) but a spiral fluted tap is different from a spiral pointed tap. I do not have any spiral fluted taps but lots of gun taps( spiral pointed ) I don't have a current enco catalog to verify what they are really called. but the point is they cut much better than the regular taps. bill

 

[jocat54]

I thought I would update this.
I drilled one hole at 21/32" (.656, supposedly 75% thread) and it was pretty tough going. The other 3 holes were drilled at 43/64" (.6718) which is suppose to be a 60% thread and they were much, much easier to tap and seem to work just as well.
Thanks for all the replies.