Help - Machining slim rod on the lathe

[Wongster]

Thanks guys.

I forgot to add that I was not tapping under power. Should have used a centre with the tap wrench instead. Totally forgotten about the centre which I used the previous time.

For the first hole, it went in ok till the last bit. I realized that I don't have any feel when tapping with such small tap. The spring loaded centre is a great idea. But I've to make it first... always have problem finding the right size spring.

The drill that was recommended is 1.6mm. How big should I go? 1.8mm? I'll try to get the suggested spiral flute tape tomorrow.

Regards,
Wong

[EdK]

(04-01-2013, 10:52 AM)Wongster Wrote: Thanks guys.

I forgot to add that I was not tapping under power. Should have used a centre with the tap wrench instead. Totally forgotten about the centre which I used the previous time.

For the first hole, it went in ok till the last bit. I realized that I don't have any feel when tapping with such small tap. The spring loaded centre is a great idea. But I've to make it first... always have problem finding the right size spring.

The drill that was recommended is 1.6mm. How big should I go? 1.8mm? I'll try to get the suggested spiral flute tape tomorrow.

Regards,
Wong

For an M2 x 0.4 thread the recommended drill is 1.6mm.
For an M2 x 0.25 thread the recommended drill is 1.75mm.

Hope that helps.

Ed

[DaveH]

Wong,
Try with 1.7mm use plenty of cutting fluid. If you feel it is getting 'tight' withdraw the tap completely and give it a clean as well as cleaning the hole out, air blow should do it. Try it again.
If you feel it is still getting too tight then you may have to use a 1.8mm drill, so long as the set up isn't moved it shouldn't cause a problem re-drilling it.
Don't forget to keep it 'square' take it slow and careful, try to feel it and watch carefully the tap isn't twisting too much. Keep backing off.

DaveH

[Wongster]

Ed, I was using 1.6mm drill. The first hole seemed ok till I reached the last bit.

Dave, I'll try again with 1.6mm but this time using a centre to line up the tap. What I did, come to think about it, was silly. The drill chuck was used to hold the tap while I turn the 4 jaw self centering chuck when starting the thread. That's why I don't have any feel.

[f350ca]

Wong
I often start taps that way, even under power, when the tap slips in the drill chuck I start using the handle. maybe leave the drill chuck snug not real tight. The hardened shank on the tap won't hurt the jaws when it slips.

[Tony Wells]

I'd recommend a spiral point tap rather than a spiral flute tap. Spiral flute taps tend to "unwind" and grow larger as they get tight, taking even a deeper cut. This is an advantage when power tapping, because when you reverse them, the "relax" and don't drag very much on the way out. But you're hand tapping. Spiral point taps are a bit stronger, but you must allow for the fact that they throw the chip forward, so either you must have enough hole dept to allow for the chip, or back out frequently to prevent the chip from binding up.

[Wongster]

Thanks guys.

Been really busy at work, no time to play. I bought 2 spiral flute tap 2 days back. Didn't know about such thing call spiral point tap then. Would have bought one otherwise just to test things out.

Greg, I never try power tapping before. Sounds scary to me. Is it easy? Will it work for small tap like M2?

Regards,
Wong

[Mayhem]

I never knew that a spiral tap would unwind. I suggested a spiral tap as opposed to a spiral point tap, as the hole is blind.

[f350ca]

Not familiar with metric sizes Wong, i just threaded some 8-32 under power into DOM tubing, which is fairly tough.

[stevec]

(04-04-2013, 09:50 AM)Mayhem Wrote: I never knew that a spiral tap would unwind.

I find that a little hard to fathom too! Going by the hardness of HSS I can't see much "unwinding" beyond SNAP!
I love spiral point taps and if it's a blind hole I try to drill as much as double the depth I need to tap.