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Is there a new standard for taps?

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Robin01/09/2018 19:18:41
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312 forum posts

Have I missed something?

I thought that the top part of a taper or a second tap would be the same as the plug. A completed thread. But appartently not.

Two new sets of HSS (ho ho) taps M5 and M10 ISO coarse. The screw doesn't fit until I run the plug. Won't even start.

Out of curiosity I put my calipers across the top three flutes of the M5 set, An odd measurement but one I would expect to be the same for all three.

Taper 4.25mm

2nd 4.48

Plug 4.73

My fault, I have now hung my head and bought Presto.

Andrew Johnston01/09/2018 19:30:51
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4777 forum posts
538 photos

There is a story that the taper and second taps are slightly smaller than the plug; but I can find no reference to same other than an obscure note in a WWII book on threads and threading. It might have been true for older carbon steel taps but certainly isn't the case for modern HSS steel taps.

However, the size differences you measured are much larger than I'd expect for the above. They may be serial taps. In a set of serial taps each tap is bigger than the previous one, the last tap being on size. Percentages may be something like 33%, 66% and 100% of thread depth. They're intended for difficult materials like stainless steel and other nickel alloys like inconel. They don't seem to be common these days. The only company selling them that I'm aware of is AecEuroTrade. And since I noticed they had some serial taps in the clearance section recently they may be discontinuing them?

Andrew

Robin01/09/2018 19:42:28
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312 forum posts

I drilled 8.5mm, squared up with an M10 taper and it wound clean through, a one finger spin.

I thought so0mething odd here.

I put the 2nd all the way through my 12mm plate. Tried to put in a set screw and it wouldn't start.

Had to run the plug before the screw would fit.

If these were not advertised as "serial taps" can I legitimately send them back?.

JasonB01/09/2018 19:55:31
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Sounds like you bought a set of sequential taps, do they have grooves cut around the shanks like the set on the right in this photo?

photo 47.jpg

Edited By JasonB on 01/09/2018 20:04:08

SillyOldDuffer01/09/2018 20:12:49
4591 forum posts
980 photos

I think they're worth keeping.

Ordinary ISO529 'taper, second, bottom' hand-taps aren't recommended for threads deeper than 1.5 times tap diameter. Instead serial taps, defined by DIN352, use three taps of gradually increasing size to thread deep holes or alloys that risk breaking an ordinary tap. The down side is having to run all three taps to finish a thread..

Presto sell DIN352 taps as well as ISO529.

Dave

Lambton01/09/2018 20:32:59
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678 forum posts
2 photos

Robin,

Keep them and use them. I have bought several sets of these from ARC and find them very good. They reduce the risk of tap breakage in smaller sizes and reduce the effort needed especially in larger size e.g. 12mm.

I appreciate that all three have to be used in sequence but this is no trouble unless you are tapping a lot of holes.

Eric

Robin01/09/2018 20:34:44
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312 forum posts

Keeping? When the plug tap went pop the whole set became as useful as a chocolate teapot.

Neil Wyatt01/09/2018 21:04:03
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Posted by Robin on 01/09/2018 19:18:41:

Have I missed something?

I thought that the top part of a taper or a second tap would be the same as the plug. A completed thread. But appartently not.

Two new sets of HSS (ho ho) taps M5 and M10 ISO coarse. The screw doesn't fit until I run the plug. Won't even start.

Out of curiosity I put my calipers across the top three flutes of the M5 set, An odd measurement but one I would expect to be the same for all three.

Taper 4.25mm

2nd 4.48

Plug 4.73

My fault, I have now hung my head and bought Presto.

In short, yes!

You've bought serial taps which are much better, but seriously misunderstood.

On a deep hole with taper, second, plug you may have to run through all three taps a few times in turn. With serial taps you can go all the way first time with the 'rougher' (one ring) then open up with the others.

I much prefer them.

Neil

John Reese02/09/2018 00:17:10
772 forum posts

I usually use plug taps. I have no problem tapping holes full depth in one pass. Only when I need threads full depth in a blind hole do I use a bottoming tap. I have a few taper taps that I inherited but rarely use them. They are good when hand tapping. They align themselves with the drilled hole for straight starts. I prefer using either spiral point or spiral flute taps. Wherever possible I tap under power, either with the mill or the lathe.

I am aware of the existence of serial taps and the benefits of using them in difficult materials. I have searched but have been unable to find them from US vendors.

Mark Rand02/09/2018 00:46:21
740 forum posts

Note:- Bottoming taps in the US are plug taps in the rest of the world. Plug taps in the US are second taps in the rest of the world.

I also use helical point/gun taps in any sizes that I've got them. They need less torque than hand taps and only a single pass. I've had very good results with thread forming taps in projects that needed lots of threaded holes. They're brilliant with a tapping head, even on silver steel/drill rod devil.

 

Edited By Mark Rand on 02/09/2018 00:57:54

JasonB02/09/2018 07:35:09
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For sombody new to the hobby buying their first taps in a particular size then a general purpose hand tap is going to be the best bet, they will work in all materials and can be used for both shallow and deep holes and have been used like that for years in both trade and hobby situations.

If your first but are sequential then their slight advantage in deep holes or certain materials is out weighed by the PITA of having to use all three taps. I did 16 holes in a part last week and was able to do that with just the taper, would have been a right faff having to do it 54times if I only has sequential.

No wonder Neil takes so long on his steam engineswink

I have become a convert to spiral flute taps recently and they are no what I reach for if I have then in the particular thread I want. One tap does all and has a very small lead taper so can get to the bottom of most holes.

Neil Lickfold02/09/2018 07:42:36
562 forum posts
102 photos

Serial taps out here, is the taps that different thread pitch diameter. Yes they have a single ring being the 1 undersize and the 2 rings being the 2nd undersize tap. Usually the smallest thread pitch diameter is on the 1 ring tap.

Most taps will be like M6 X 1 H7 with the H7 being the thread limit range of that particular tap.

Andrew Johnston02/09/2018 08:45:00
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4777 forum posts
538 photos

I've never used, or felt the need for, serial taps, with the exception of some home made taps for a square thread:


finished_taps.jpg

For general hand tapping I often use the standard set of three taps, although for through holes I only use the taper tap. There's no need to use the 2nd or bottoming tap unless the hole is blind. For hand tapping blind holes I use a spiral flute tap in preference, although they are a bit trickier to get cutting to start with.

For machine tapping I use spiral flute, or spiral point, depending upon whether the hole is blind or thru. I've got some form taps, but haven't experimented with them yet.

Generally most materials are no real problem to tap. Some plastics have a tendency to close up after tapping so may need several passes. The only material I've had real problems with is tungsten alloy. After unsuccessfully trying a number of expensive taps for "grippy" materials I found that a worn set of Dormer hand taps worked best. smile o

Andrew

Russell Eberhardt02/09/2018 10:45:11
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2476 forum posts
85 photos
Posted by Neil Lickfold on 02/09/2018 07:42:36:

Serial taps out here, is the taps that different thread pitch diameter. Yes they have a single ring being the 1 undersize and the 2 rings being the 2nd undersize tap. Usually the smallest thread pitch diameter is on the 1 ring tap.

Same here in France - confused me a bit at first.

Russell

Dan Carter02/09/2018 11:34:12
81 forum posts
8 photos
I can't power tap m12 in lathe or mill as either the tap slips in the drill chuck or the belt slips on the lathe. Just bought M12 serial taps and works perfectly
Anthony Knights02/09/2018 11:49:05
263 forum posts
84 photos

The first set of metric taps I bought (3 to 12 mm) were serial type with the blank, single and double grooved shanks.

Never had a problem using them and even though I've had them for 10 years I've not broken one yet, Probably tempting fate putting that !

Robin02/09/2018 20:57:48
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312 forum posts
Posted by Andrew Johnston on 02/09/2018 08:45:00:

I've never used, or felt the need for, serial taps, with the exception of some home made taps for a square thread:


finished_taps.jpg

Those are adorable, do they work?

Robin02/09/2018 21:03:13
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312 forum posts

I have ordered 100 grams of aluminium potassium sulphate to dissolve out the broken tap. A new experience for me, looks like fun.

Andrew Johnston02/09/2018 22:14:26
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4777 forum posts
538 photos
Posted by Robin on 02/09/2018 20:57:48:

Those are adorable, do they work?

Of course! smile

The threaded embryo nuts:

square threads.jpg

And the finished nuts with the brake shafts:

finished brake shafts.jpg

The square threads are 0.5" OD and 8tpi.

Andrew

Marcus Bowman02/09/2018 22:33:54
161 forum posts

Some years ago I bought a pair of Dormer M12 x 1 serial taps. At that time, it was difficult to find a stockist, and they cost around £35 per tap. They were for a specific job I repeat regularly, so I had to bit the bullet on the price. The tailstock drill chuck grips them more securely than smaller non-serial taps, simply because the turning forces involved are smaller, despite the larger thread diameter.

More recently, I bought some sets of serial taps in more common metric sizes, at much more reasonable cost. However; they are TiN coated and distinctly less sharp than the original Dormer uncoated HSS taps. That was a surprise, and largely negated any advantage in the small thread sizes (M6 and M8).

Surprisingly, Dormer serial taps are even more difficult to obtain nowadays, although I also suspect the price may be even more difficult to justify. Sorry - Dormer Pramet, as it now is.

Like JasonB, I favour spiral flute taps, and it is a joy to use them in a tapping head on the drill press.

I have always used Trefolex paste when tapping, but I recently bought a bottle of Dormer tapping fluid. 'Twas a waste of money; its not as effective as Trefolex, so I will be happy to switch back in a few years, once the fluid is finished.

Marcus

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