3 piece taps

[GrahamRounce]

Hi all.
I have a fairly slow rechargeable screwdriver which I've successfully used with a 3mm hand tap to thread holes in 6mm mild steel.
Eventually, though, my luck ran out, and the tap broke under the strain.

I was wondering about using a 3-piece set to replace it (consisting of a light taper, a medium cut, and a final cut) on which there would be less strain.

Apart from the bearable hassle of changing taps in the screwdriver, I'm concerned that taps 2 and 3 might not properly follow the shallow thread made by tap 1.

Can anyone with 3-piece tapping experience advise whether that's likely to be a problem, and if so suggest how to get around it? Manually fitting eg tap 2 into tap 1's thread DOES sound like a hassle!

Thanks,
Graham R.

 

[TFrench]

Spiral fluted taps are for power tapping, but tbh for an M3 thread I'd be doing it by hand where you've more chance of feeling if you're going to snap the tap.

 

[Sachakins]

If its a through hole then running tap right through wouldn't need to use the others.

 

[Yojevol]

Far better to learn the art of tapping by hand. You get to feel what's going on. Some points to note: -
1. Use a cutting fluid for lubrication
2. At the start check frequently that the tap is in line with the hole.
3. Back off at least every quarter turn to free the swarf
4. Using a 3 tap set is not a problem. Each tap prepares the way for the next.
5. For 6mm steel the taper tap will do the job in one hit.
6. For blind holes the depth needs to be sufficient to allow the taper tap to go well beyond the required full thread length.
Can't think of anything else at the moment
Brian

 

[GrahamRounce]

Thanks - I should have been a little more explanatory...

I've always tapped by hand: +oil, forward 1/2, back 1/4, depending how it feels, but this time I had 56 holes to tap, and the electric screwdriver was just an experiment which seemed to work (surprisingly?) well on all 56. But when I came to the next batch of 28 it broke on the second one. (Typical)

So I've ordered 2 more, tapered, but on third thoughts maybe I should have gone for "machine" taps with twisted flutes. Would they really clear the swarf better?

 

[GrahamRounce]

PS Thanks for pointing out that for through holes I don't need a 3-piece set!

 

[Daniel2]

Thanks - I should have been a little more explanatory...

I've always tapped by hand: +oil, forward 1/2, back 1/4, depending how it feels, but this time I had 56 holes to tap, and the electric screwdriver was just an experiment which seemed to work (surprisingly?) well on all 56. But when I came to the next batch of 28 it broke on the second one. (Typical)

So I've ordered 2 more, tapered, but on third thoughts maybe I should have gone for "machine" taps with twisted flutes. Would they really clear the swarf better?

Yes, they will.
A spiral flute tap is the ideal tool for what you're trying to do.
You don't need to keep backing off, you can just power through
in one go.

 

[GrahamRounce]

Okay! Off I go! Thanks!

Whilst on the topic may I ask about an adaptor for the taps, standard 1/4" hex male to 4mm square female? (At the moment I'm overtightening the tap into a 3-jaw chuck - not great.
Thanks again,

 

[GrahamRounce]

Oops. ...to 1/8" square, I meant

 

[bourbon]

I use UK drills, give them a bell and ask for advice

 

[clogs]

there are proper adaptors to get a square tap into a 3 jaw chuck.....
but at times crazy prices...I've been looking for years.....
where poss in the lathe or milling machine I use ER collets.....
even thought about getting a socket set from the likes of Snap on that are ment for suare headed stuff.....
but again cost re very high......
very soon I need to drill n tap around a 100 12mm holes in 8mm plate but up a ladder.......that could be fun.....
so looking for one of those combined drill and tap thingy's....
perhaps they may help u....

 

[TFrench]

If its a regular thing to be tapping this many holes, might be worth getting something like this for your pillar drill
https://www.ebay.co.uk/itm/362756223597?epid=3019319980&hash=item5475f4b26d:g:U5EAAOSwHHRa9oi4

 

[Sideways]

Metabo make a cordless power tapping drill that is very nice and of course not cheap. I don't know if it will take an M12 tap though.
Fein cordless drills with the quick change chucks can take a tapping adapter but lack the auto reverse of the Metabo.

 

[GrahamRounce]

Thanks for all the help.
One last comment, which is why use a straight-fluted tap at all? Is there some benefit when tapping by hand?

I had thought of using the pillar drill, but then realised the tap needs to be free to make its own path. That tapping head looks on the expensive side. The auto-reverse (also wrt the Metabo) seems a luxury I can do without for now.

Cheers, and Merry Christmas!
G

 

[Fergie 307]

The straight flute taps are good for hand tapping as the taper or first tap will self align in the hole, to an extent at least. Spiral taps really need to be held properly in alignment. If you have to do loads then it's well worth getting, or making, a siding tap and die holder.

 

[GrahamRounce]

Did you mean "sliding"?
Funny you should say that! I've just knocked up this:

The plug cutter is held in the pillar drill chuck. The 12x12 bar "floats" in the plug cutter. The tap is fixed in the 12x12 bar. It travels down nicely, but you have to be quick to lift the drill+plug cutter off the bar before the tap goes past the end.

Removal is manual, but I'll cut a slot for the electric screwdriver to speed things up.

 

[Fergie 307]

Exactly, blooming auto correct got me again. Simple but really useful tool.

 

[Fergie 307]

And I would say always go for good quality HSS taps, they cost more than the cheap ones but last a lot longer and are generally more accurate. Tracey tools are a good source.

 

[GrahamRounce]

Thanks. In my case I don't usually need great accuracy, but I do like them to not break! HSS are better from that point of view, as well?

 

[Sideways]

Machine taps with a spiral for clearing the swarf are very handy in a power drill for repetitive easy work like tapping aluminium or thin steel.

It's not ideal but they will grip in a drill chuck as long as you are not pushing them hard.
Machine taps come in different colours (painted ring) according to what you want to tap (mild steel, alloy steels, cast iron, stainless, non ferrous etc. Most are compatible with more than one material. This blue one for example is for steel but OK for aluminium.