Tapping defects 1

[pvkraju5]

Hi
Recently We have tapping problem in manufacturing component and the details as under one of the component steel material having M30 Nut for that locking screw M5 threading for that we have done drilling 4mm drill then we have done tapping M5 tapping by hand for that we have observed NO GO answering gauge

What could be reason NO GO Answering gauge?

Same process (drill and same tapping) carried out on one dummy plate on that Thread gauge GO answering and it is OK.

Here my question is what could be reason for threading NO GO Answering?

If anybody having in this Please help

Thanks & Regards,

P V K Raju

 

[MikeHalloran]

Depending on the pitch, you should be drilling with a 4.2 or 4.5 mm drill before tapping M5.

Too small a tap drill is likely leaving distorted threads.



Mike Halloran
Pembroke Pines, FL, USA

 

[pvkraju5]

Hi
Thanks for immediate response
Threading M5x0.8 pitch for that we have found after drilling hole dia 4.2mm only, And also we suspect that if larger dia hole could be thread may be play.

Shell we do increase the hole size up to 4.5mm?
Please suggest

Thanks & Regards,
P V Krishnam Raju

 

[MikeHalloran]

The tap drill basically provides clearance for the core of the tap to go into the workpiece, and a place for the generated chips to travel or accumulate; it has relatively little effect on the pitch diameter of the threads produced by the tap.

You should consult with your tap supplier. One thing you need is a basic tap chart, that helps you select a tap drill for each given thread. There may be reasons to adjust the tap drill size somewhat, but 'play' is not one of them.

To control the 'play', you can adjust the tapping speed and/or the lubricant, and, primarily, you can buy taps of slightly different sizes above and below the nominal in order to produce exactly the thread you want. Again, your tap supplier will be happy to help.



Mike Halloran
Pembroke Pines, FL, USA