Fadal Rigid Tapping

Rigid Tapping-Fadal 4020 Trying to help a customer out that is having problems (spiral taps breaking) 1/4-20 .800 deep,blind hole. The material is 304ss. Any help would be appreciated. Thanks in advance


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Dave B
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Try increasing the drill size. This will reduce the % thread, but if the application is not critical, you can get by with less thread.

Also, try a thread forming tap. They are much stronger, don't pack chips and in some materials yelid a stronger thread.

Good luck


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My first choice would be to use form tap if wall thickness allows.

Next COOLANT if water soluble run rich. For recommended oil/coolants it has been discussed in this group a number of times.

Is machine speed correct? I would start off at the high end of recommended speed by manufacturer. Often running slow/slower is the worst thing to do. Is machine feed correct? Is the hole diameter size correct? Is the drill walking? Is the drill diameter depth deep enough? Is the hole chamfered? Is tap in alignment with drilled hole? Is tap spinning in holder?

During cycle how are the chips forming? Are they always coming out of the hole cleanly or sometimes packing?

Peck Tapping cycle; don't know what controller they have or if it will even work on Fadal but on Fanuc I sometimes use a peck tap cycle (rigid tapping "ONLY"). By putting a "Q" into the rigid tap cycle (like a peck drill cycle) it will peck tap the hole. Worked on Fanuc

21i and may work on others even though I have never seen it in any Fanuc manual.


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I'm not aware of any special "Peck" tapping cycle for Fadal controls. But it's easy enough to use multiple regular rigid tap cycles with increasing depths on the SAME hole. As long as the start parameters stay the same the tap will enter at the same point. But if on pulling out there are chips hanging on the end of the tap, they could bind on reentry.

Has anyone mentioned thread milling?

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good pointers

also add:

Tap running concentric ?

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