Band Markings on Taps

[hexreader]

Sorry to be such a noob, but that's what I am...

I have a tapping set that comes in 3s;   this one

I have tried google without success.

What is the significance of the banding markings please?

I have been tapping (M10) in the sequence - 1 band - 2 band - no band

Am I doing it right?

Do i need all three taps, or would two do?

All advice or hints gratefully received....


Many thanks,

Robin     England

[PixMan]

Those bands are manufacturer specific. Some makers use colored bands as code for what materials the tap is engineered to cut.

What you have there is what we (here in the US anyhow) as being "series" or "serial" taps which are a series of three for progressively larger thread pitch diameter. What we do differently here is make all taps to a given "class of thread" (meaning thread pitch diameter limits) and it's one tap, one pass to finished pitch diameter.

When we find hand taps in sets of 3 here, it's three different lead styles. One with a long 6 to 12 pitch lead is a "taper" and serves to act as your series taps do by taking progressively more material as you wind it in. The second is a "plug" tap, with 3.5 to 5 leads of thread. It's the most popular, most common one if you buy just one tap. The third style is a "bottoming" tap with 1.5 to 2 leads of chamfer. It's used just as you think, to get threads as close to the bottom of a blind hole are possible. Typical application would be to use a taper or plug tap (rarely both in succession) to start the blind hole, then use the bottoming tap only to finish the last few threads. The pitch diameter for the bulk of the thread is already finished.

I've never really understood the need for those serial/series taps. One & done is how I use most every tap in my shop, and 99% of the time it's with high quality HSS, HSS-Co or HSS-PM machine taps.

You are probably using your correctly, though all you have to do for assurance is measure the O.D.'s of them.

[DaveH]

Just to carry on from Ken (PixMan) - When metric threads became standard (in Europe) it was decided that the 1st or taper taper tap would have a longer and different (angle) taper than the imperial taps (BSF / Whit). The idea being if one uses the correct drill for the hole then the taper tap because of it's taper will tend to go in square with out too much trouble. Well that was the idea.
If I am taping a hole on the bench I will always start with the taper tap and then either the second or bottoming tap depending on how I feel  

If I start the taping on a machine (lathe or mill) I nearly always use the second tap because the machine will keep it square.

On a blind hole I always use all three taps especially on taps 6mm and under using all three taps allows for a gradual removal of material by each tap and doesn't put undue force on one tap.

 
DaveH

[hexreader]

Thanks PixMan and DaveH,

Still a little confused on which order I should use the taps, but the way I am doing it seems to be working.

Forgot to mention that I am tapping 3/8 inch steel and already blunted a carbon steel tap after only 2 holes out of 70.

HSS taps seem to be working a lot better and I think I will continue to use all 3 taps for this job, then revert to single tap for easier jobs.

Not convinced that any of the 3 taps are bottoming taps (which was what I was expecting) since all have differing tapers. But no issue, as I am not tapping any blind holes.

Appreciate the hints... Many thanks

[DaveH]

(11-21-2015, 05:35 PM)hexreader Wrote: Still a little confused on which order I should use the taps, but the way I am doing it seems to be working.

Appreciate the hints...    Many thanks

Start with the one that has the 'most' taper (longest)
Then with the one that has the 2nd 'most' taper
Finally the last tap should only have a small chamfer on the end - may be two threads.

Just 'cause I'm nosey what size tap are you using?

You could post  a pic of the taps we may be able to help from the pic.

DaveH

[DaveH]

Robin,
I have checked on line .............. google "hand taps'
This is the order
Tap with 1 line .............. start with this tap 1st tap to use
Tap with 2 lines ..............2nd tap to use
Tap with 0 line ................3rd or last tap to use.

Here's a pic
   

 
DaveH

[hexreader]

M10

England is now mostly metric.

Camera batteries are dead - will get more tomorrow, but the taps look exactly like your picture. Your Googling skills are way better than mine: I spent ages searching without finding the answer. Many thanks for solving the mystery.

Please be as nosey as possible. I appreciate the help.

[DaveH]

Robin,
Use some cutting fluid if you have some - if not use some oil - any oil will do better than nothing.

Because the material is 3/8" thick using just two taps will do the job fine, but always start with the 1st tap - the one with 1 line. Depending how far you go down with this tap will allow you to use either the 2nd tap (the one with 2 lines) or you may be able to go straight to the final tap - the one with no line.

Do use some cutting fluid - it does help 
And do clean the tap after each and every use
 
DaveH

[Vinny]

70 of 'em?! Get a gun tap and a tapping head for the drill press.

[arvidj]

The excellent descriptions provided are for tapping blind holes all the way to the bottom of the hold. But you say you "But no issue, as I am not tapping any blind holes."

I am no expert but can think of two situations where just the one-line tap would be all you need.

What appears to be your case where the hole goes all the way thru ... i.e. no bottom. There is not benefit to using anything other than the first tap. Just run the tap in so the main body of threads have gone thru the hole [you will feel when it is no longer cutting and simply screwing it itself into the plate]. I then clean the crap out of the hand tap with a brush and then back it out of the hole. A gun or spiral tap may not have as much crap in it as a hand tap so the step could be avoided, and I am sure there have been a bazillion holes tapped without bothering to clean the tap before unscrewing it so I am probably just wasting my time there. 

The other situation, which does not appear to be yours, is where you do have a blind hole but it is deeper than needed for secure attachment. I would then just run the first tap in far enough to provide sufficient threads to hold things together. Cutting threads all the way to the bottom of the hole doesn't add any value assuming the length of the bolt is appropriately sized ... as in long enough to hold things together yet not so long that it will end up in the uncut portion of the hole.

Of course if you are working on an airplane or space vehicle please ignore everything that I have suggested.

And as Vinny pointed out, for 70 holes some type of machine would be great ... be it a drill press with a tapping head or robust variable speed hand drill with a block or some other device to ensure that the tap will start in the hole correctly. A hand drill without an alignment device will be a disaster.

Which does beg the question ... how did you put 70 holes into what ever it is in the first place? But I digress.

And as I said, I am no expert so any corrections or concerns about what I said would welcome.