Taps & Dies

The Taps & Dies that I have, and use, are ordinary ones that were not expensive.

i would like to know what the difference, and benefit, there is in have HSS Taps & Dies. On checking the Internet they are certainly a lot, and I mean a lot more expensive than the "ordinary " ones.

Thank you in anticipation for your replies.

I use a lot of HSS BA sizes for my business down to number 14. One thing that I've found is that breakages are a thing of the past. The finished threads are certainly cleaner. Definitely worth the expense.

Simon

A lot depennds on what you are using them for If you work mainly in brass carbon taps and dies are adequate

if used with care

Roy

In my experience they don't break as easily and give a better finished thread because they are usually a higher quality product.
You also usually get all 3 taps in a set.

Steve

Cost of HSS taps vary very widely. They come in 2 style, ground thread and cut thread. There are also variations in the grade of HSS used. They needn't be expensive, these for instance which in real terms are ok

**LINK**

In terms of ground and cut thread one thing I have noticed is that taps these days tend to measure slightly over size. I'd guess this is some sort of standard where as some time ago taps tended to measure exactly on size. Same sort of idea as a reamer - the size they produce is very slightly greater than their diameter.

Dies come with the same variation except at very small sizes I doubt if ground thread can be found. BA for instance are usually all cut thread. The other difference is button and split dies. Personally I will only buy split as they can be adjusted a little if the usual die stocks are modified.

The problem with carbon steel taps and dies is that often especially in sets they aren't made very well. In the past there have been high quality ones available. There probably still are from true industrial suppliers but they will probably cost more than cheap HSS.

Well made carbon steel taps and dies are fine on most materials but can be a problem on materials like stainless steel. The other aspect is how often they are used as they will wear out more quickly than HSS. The harder the material the faster they will wear out.

I recently bought a cheap used set of M8x1.25mm left hand thread taps and a die in carbon steel. Made by these people

**LINK**

The fact that they are carbon steel doesn't bother me as they wont be used very often. They are dead sharp and accurately sized by modern standards at 8.05mm dia. For odd jobs I would still buy carbon steel if the price is right and the quality adequate. Breakages of both types really depends on how they are hardened. The usual reason for breakages in very small sizes is twisted holes down to poorly sharpened drills / drilling machine spindle not being square to the work / the tap being put in at the wrong angle and aspects like that.

Cheap carbon steel full sets ? I needed to cut a few UNF sizes some time ago and thought why not so bought a set. The holders were pretty useless and worse still the dies especially wouldn't really cut. The taps could with a lot of force. I didn't go for the cheapest of the cheapest either. These days I would just buy the ones I needed rather than doing the same thing again. Although I work in imperial the majority of my taps and dies are metric. If I was following some design that wanted say 1/4in BSF I would simply replace it with M6 if I needed to. BA can be replaced easily. I also have most of the usual sizes of ME especially in 40TPI. ME is unique and can't really easily be replaced with standard metric taps and dies.

Thought I had better add why the set was so bad. I suspect that they had never been near a grinder even for final sharpening along the flutes. Something to watch out for when buying.

John

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Edited By John W1 on 11/08/2015 10:35:25

> Thought I had better add why the set was so bad. I suspect that they had never been near a grinder even for final sharpening along the flutes.

A run along the face of the flutes with a small round stone in a dremel can touch up such taps and dies. Done with care any loss of diameter is negligible.

Neil

Might be good way of getting them to the size they should be Neil with a suitable jig.

Size wise those Arc taps don't seem to be any better or worse than others. I'd guess more could be paid for them elsewhere.

I bought most sizes just in case I need to tap stainless again. If I needed to do that often I would be looking for HSSE/5% cobalt or even M42. One size was out of stock and I sort of requested they sent me them FOC for postage at least when they are back in stock - Fat chance.

John

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I suspect that the difference people notice between carbon and HSS taps has more to do with manufacturing quality that the material. In home workshops we don't run taps at speeds that would generate enough heat to soften carbon steel taps.

Russell.

I think carbon steel is usually cut thread whereas HSS is ground thread which may account for the difference in the finish of a thread.

Ground taps are straighter, sharper, dearer, and generally made from HSS.

Cut taps can distort on hardening, the edge is dulled by heat treatment, they are often cheap, and they are generally made from carbon steel.

There are lots of other distinctions between different styles of taps - length, angles of grind, helix, and most recently, surface coating with nitrides etc.

Cheers, Tim

That's because threads are specified with various tolerances of fit. The most common, for general purpose use, is ISO2, aka 2B or 6H depending upon the country of origin. This is what you normally get if no tolerance is specified when buying. To ensure fits with most externally threaded parts taps are usually ground at the upper end of the tolerance, ie, oversize. It also ensures a longer life, as the tap takes longer to go out of tolerance as it wears.

Better quality taps have the tolerance grade marked, like this tap I bought recently for work:

Andrew

Thanks Andrew as I have wondered about this.

I still suspect standards have something to do with it. They are generally established in conjunction with the people who manufacture who will look at it from an ease of production point of view so once established no one tries to do any better.

There are some excellent examples about. Nuts and bolts. GKN used to churn out fantastic numbers at very low cost that had a much better fit than they do these days, I have bought precision bolts for clamping things and I would say that these do tend to be close to the rights size and cost a lot more. Another example is the occasional ebayer that comes across some cut thread screws and nuts. The fit is generally excellent, just short of interference. A weirder one that I came across due to work is HGV brakes. Once up on a time people sat down and said ok lets make this truck stop - now they want to meet a standard. In both cases due to checks they wouldn't be "bad" anyway. That sort of sums it up. Some trucks used to stop quicker than others now they are all likely to be much the same. Sometimes standards are good sometimes i feel they are a bit questionable and the limits have been set wider than they need to be. One thing I gather from your post and measuring them is that ISO 2 results in pretty narrow range of measured sizes. I'd guess nuts and bolts are just the same but I just use them.

At least at home we don't have to use traceable items otherwise we would have to buy taps stamped with a tolerance and even checked to it. Yet - maybe the boiler people .................?

John

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Edited By John W1 on 12/08/2015 13:35:57

One thing that was emphasised in the documentation that I reviewed to check my facts is that taps do not cut to a specific tolerance, as there are too many variables, and no adjustment, unlike when producing external threads. Internal threads are also extremely difficult to measure directly. The standard method to check tolerance is to use a go/no-go gauge. For such a seemingly simple mechanism screws threads are pretty complex when one digs down into the detail.

Andrew

For John W1:

If there were no standards we would all spend hours making spanners.

Quite how we would manage making the tyres for our vehicles' non-standard wheels, or sparking plugs for our non-standard engines, I don't know.

All engineering is compromise. Standards allow us to rely on compromises that are known to work.

regards, Tim

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I propose a big vote of thanks to Sir Joseph Whitworth

... and a round of Jeers to those who messed-up his work.

MichaelG.

Have you ever owned a set of whit spanners?

And Tim hex heads and the likes have nothing what so ever to do with the type of standards I mentioned - only the tolerance on them.

John

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If ever you wish to produce a slightly smaller size tapped hole to give a "snug" shake free fit on a commercial bolt/screw, then using the number 2 tap from a serial tap set ( 2 rings) will give the desired result.

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Well, not a full set, John

... But I do have quite a few.

MichaelG.

One of the things with cut taps, rather than ground taps is burrs. Have a look at a cut tap with a loupe, and you will see lots of burrs.

Now this may be ok if you are tapping big (over M6) in steel or cast iron. However if you are cutting small or fine threads in al.alloy a cut tap is likely to produce a fairly bizarre thread.

I always by taps and dies as required, and never in sets. These days I buy the best quality that I can. Yes they can be very expensive.

cheers

Bill