HSS or CS taps and dies

Excellent video, the swarf behaves exactly as I would expect with a spiral flute tap.

Andrew

A big generic difference between carbon steel and high speed steel taps is that carbon steel ones may have been turned then hardened, whereas high speed steel ones are almost invariably hardened then ground.

A big generic difference between carbon steel and high speed steel taps is that carbon steel ones may have been turned then hardened, whereas high speed steel ones are almost invariably hardened then ground.

.

It's a joy to see those spirals just dancing out of the hole.

... very impressive.

MichaelG.

I'm very supprised to see so many recommendations for carbon steel 🤨 In my experience HSS is superior in almost every aspect. They are less brittle, seem to cut nicer threads and they stay sharper for much longer. My advice would be to buy the sizes you use most often loose. If you shop around on ebay you can often pick up new taps from top quality brands like presto, dormer and skf for a fraction of the price.

.

I think your "in my experience" probably explains it

Not all 'carbon steels' are equal

... and for that matter, not all 'High Speed Steels' are equal

Mark's comment is also very pertinent.

MichaelG.

Yes that is true. But you seem to be implying I don't have much experience. Belive me Ive tried the lot. I have good quality British made carbon steel taps from the likes of Hall, Osborne, and Clarkson. They are about on par with a low to mid range HSS tap.

Almost all mine are HSS as I do find them less prone to breakage. On that point, I think drilling the correct size pilot hole plays a bigger part in tap survival than the material it's made of and assuming of course it's sharp.

Taps are quite easy to sharpen and can be touched up with a stone.

Or like this:

Although strictly the picture shows the relief being ground from scratch on a home made tap.

Andrew

Interesting that most people seem to think that good CS taps are probably the best way forward. It is certainly my experience. Everyone says that CS taps are more brittle and break more easily than HSS versions. This is the exact opposite to my findings. I have never broken a CS tap, but plenty of HSS ones! I wonder why this is? If I didn't have the contrary experience, I would have surmised that CS taps were more prone to breakage.

Having said all that, I bet I get lots of CS taps breaking now. The workshop gremlins will see to that!

Andrew.

.

Far from it !!

I'm sure that none of us has experience of the whole gamut of both ranges.

MichaelG.

Edited By Michael Gilligan on 21/05/2019 13:08:14

The forum likes to simplify, asking very broad questions like this one. Quite often there's a useful general answer that's not completely trustworthy.

In this example there are several types of HSS and many varieties of Carbon Steel. HSS and CS are alloy families, not individual metals that can be compared directly. Several things can be done by makers to improve the performance of Carbon Steel, and bad things can be done to HSS to reduce cost. It's a very mixed bag.

Always unwise to draw strong conclusions from a limited sample. Broadly you can expect CS to be more brittle than HSS, but it depends on what you've got. The operator is important too. Perhaps Andrew breaks HSS taps because he subconsciously expects them to be tough whilst his CS taps survive because he subconsciously fears snapping them and is more careful? Or his experience is random luck.

Most useful in this thread is the number of hobbyists confirming "Carbon Steel Taps and Dies do an acceptable job for me." It means it's probably not necessary for the average Joe to spend loads of money on the very best HSS tooling on the market. But CS getting a positive press doesn't mean buying HSS is complete waste of money either - so much depends on the job. For example, most of the time I happily thread odd holes with Carbon Steel taps. I would buy a better HSS tap if I had a lot to do and was at all worried about snapping the tap off in an awkward hole.

Dave

Hello Dave,

All of my CS taps have come from Tracy Tools and the HSS versions are Draper, Presto or Sherwood. I know now that Sherwood is probably Chinese in origin, but never the less I find them every bit as good as Presto or Dormer.

Maybe you are correct in subconscious care with CS and not so with HSS. But by now I would think that I have learned my lesson.

I always use a tapping guide if at all possible and I use Rocal tapping compound. So I must just be an odd man out.

Andrew.

You're not alone Andrew, odd results and strange contradictions fill my workshop too!

Dave

Hmm tapping compound, when I was at school we had a pot of tallow, and happily my father had a similar card board pot too. I have used lard in the past, but since my move all I have is neat oil.

I have seen people mention Trefolex and Rocal any other suggestions?

Regarding tapping drill size. For M6 I have two books, one says 5.6mm the other 5.3mm. I am tapping a 19mm deep hole so chose the 5.6mm to reduce the thread percentage and make tapping easier. For relatively deep holes what percentage thread would you use?

I always use Rocol RTD, metric size minus pitch for drilling and anyrhing over 1.5 x diameter for thread depth is a waste of time.

Martin C

To my shame, I have even managed to break a HSS M10 tap. That taught me to obey the instruction to reverse rotation every half turn to break the swarf! For lubrication, I use either Rocol STD or even Bacon fat (not too different from Tallow as used in the old days ). Any lubrication, oil or grease HAS to be better than none!

Broken taps are my fault rather than the material.

Still, my preference is for HSS rather than CS, (Have some, but tend to avoid their use because of my ability to break them ).

Wherever possible, I use a tapping guide, or fixture, to minimise bending the Tap. The torsional loads are enough worry without me imposing bending also.

If in doubt, drill the hole very slightly oversize. The slightly reduced engagement will not be disastrous, Much less than a broken tap in the last hole in the job!

Howard

This is Tubal Cain territory (the British one, not the internet pretender) who shows that drilling the tapping hole slightly larger than the Zeus tables (within reason) makes negligible difference to the strength of the resulting thread but vastly reduces the chance of over torquing the tap and breaking it.

I dont have a specific tapping guide, but I do have a selection of Eclipse tap holders. They have a centre hole in the top, and I have made a centre to go in the drill chuck. I have a spring loaded plunger centre on the todo list, but that might just get replaced by a length of bunge tied to the drill handle.