Form tap or cutting tap for M14

blek · Jul 2, 2020

Hi all

I have some 6061 T6 I'm looking to drill and thread with an M14 x 1.00 in a manual lathe and was wondering what would be the tap type of choice for the pros, a gun nose (sprial point), or form tap?

I haven't used form taps before but I understand they can be run harder and faster with less breakages? How are they at 14mm? Would they be good for the 6061 or should I stick with what I know and go the gun nose?

Thanks all

atex57 · Jul 2, 2020

M14x1? In aluminum? Should be a walk in the park with a form tap. Drill or bore the hole to 13.5mm, good oil, and hit it at 300+ RPM. You do have instant reverse, right?

Ed.

blek · Jul 2, 2020

atex57 said:
M14x1? In aluminum? Should be a walk in the park with a form tap. Drill or bore the hole to 13.5mm, good oil, and hit it at 300+ RPM. You do have instant reverse, right?

Ed.

Hi Ed

Thanks for confirming my suspicions on the ease with the form tap. Yes instant reverse available for power tapping.

blek · Jul 2, 2020

atex57 said:
M14x1? In aluminum? Should be a walk in the park with a form tap. Drill or bore the hole to 13.5mm, good oil, and hit it at 300+ RPM. You do have instant reverse, right?

Ed.

Sorry Ed one more Q. I have heard that form tapping can deform the entry and exit, should I champer before or after form tapping?

Limy Sami · Jul 3, 2020

blek said:
Sorry Ed one more Q. I have heard that form tapping can deform the entry and exit, should I champer before or after form tapping?

I like before - and beware form taps are usually?? a lot more $$ than cut taps - especially in ''none preferred'' sizes

ChipSplitter · Jul 3, 2020

blek said:
Sorry Ed one more Q. I have heard that form tapping can deform the entry and exit, should I champer before or after form tapping?

Yes, I would chamfer. It's always a good habit.

However, when I get a large "wart" at the top of the hole I increase the drill diameter a few thou. It takes less power and the thread % is essentially the same.

atex57 · Jul 3, 2020

Chamfer before, then then any deformation stays below the surface. Use a tap made for aluminum, most coatings are not aluminum friendly.

Ed.

blek · Jul 15, 2020

Thanks for the advice all. I'm getting all my ducks in a row atm and was wondering if 1mm clearance would make much difference for the thread forming process? 17/32 (13.49mm equivalent), reamers seem to be more available then 13.5mm (a bit cheaper too), so would the 1mm make much of a difference with the fine pitch?

Cheers

Limy Sami · Jul 15, 2020

I hope you mean 0.01mm difference ????

blek · Jul 15, 2020

Haha yes 0.01mm wrote that on the go.... &#55357;&#56904;

Limy Sami · Jul 16, 2020

blek said:
Haha yes 0.01mm wrote that on the go.... ��

In that case, I'd be more worried about a fruit fly farting in Brazil.

UptownSport · Jul 18, 2020

A smart man learns from his own mistakes; a wise man from other's.

I asked precisely the same question here years ago.

Being neither smart nor wise, I really didn't listen to the advice until I found out the hard way.

1. You need to use the carriage to feed the tap at 1mm.

2. Precise reamer size is vital. It's not- and you'll understand if you think for a moment- like a cut tap- where hole size is can be a broad range-
It needs to be precise. http://media.guhring.com/documents/tech/Charts/FormTapDrill.pdf

Those two things, and it was a breeze!

Bill D · Jul 19, 2020

Any reason not to use a lower rpm for the first few until you get the hang of it? I would not think rpm made any difference in quality of the finished product or tool life, but I have never used form taps. Would the preferred rpm be similar to cutting taps depending on diameter and pitch.
Bil lD

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