HSS or CS taps and dies

[HollowpointParticipant @hollowpoint]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hollowpoint on 21/05/2019 09:26:29:

I'm very supprised to see so many recommendations for carbon steel 🤨 In my experience HSS is superior in almost every aspect.

.

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.

[HollowpointParticipant @hollowpoint]

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.

[Chris TriceParticipant @christrice43267]

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.

[vintage engineerParticipant @vintageengineer]

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

[Anonymous]

Or like this:

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

Andrew

[Andrew TinsleyParticipant @andrewtinsley63637]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hollowpoint on 21/05/2019 09:53:41:

Yes that is true. But you seem to be implying I don't have much experience. …

.

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

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Tinsley on 21/05/2019 12:58:48:

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.

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

[Andrew TinsleyParticipant @andrewtinsley63637]

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.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Tinsley on 21/05/2019 16:11:18:

…I must just be an odd man out.

Andrew.

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

Dave

[AdrianRParticipant @adrianr18614]

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?

[Martin ConnellyParticipant @martinconnelly55370]

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

[Howard LewisParticipant @howardlewis46836]

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

[Chris TriceParticipant @christrice43267]

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.

[AdrianRParticipant @adrianr18614]

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.

[EmgeeParticipant @emgee]

Posted by AdrianR on 21/05/2019 19:37:30:

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?

Hi Adrian

For Metric threads tapping drill size deduct the pitch from the diameter, so for M6 x1 tapping drill is 5mm so perhaps the sizes you mention are for fine pitch threads.
I would not use less than 60% engagement especially in softer materials.

Emgee

[SillyOldDufferModerator @sillyoldduffer]

Posted by AdrianR on 21/05/2019 19:37:30:

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?

Tapping compound – always a good idea to use something! I use CT-90 because it's what my local place keeps on the shelf. The modern mixtures have somewhat better heat, pressure and lubricating properties than old-school organic recipes. They are also unlikely to be a biohazard. In the old days lard etc would rot and cause painful infections via a scratch.

For tapping drill sizes, how strong do you need the connection to be? The average bolt isn't heavily loaded, and when more strength is needed it might be easier to use a bigger one than a close fitting thread. Production tends to avoid tight threads because making them wears out tools and slows down assembly.

Most of the time I use over-size tapping holes. However, rarely – when strength or safety matters – I use the recommended tight drill. Not often because I'm not bolting wings on airliners!

I don't think the depth of the hole makes much difference to choice of tapping drill diameter. Surprisingly few threads are needed to achieve full-strength. Perhaps 4. After that, additional threads in a deep hole don't add more strength. So, it's the same decision: if maximum strength is needed, drill for tight threads and accept the tap will wear faster and is more likely to break, otherwise drill larger holes to favour the tap.

Dave

[Ian Skeldon 2Participant @ianskeldon2]

Having read through this thread I will admit that I mostly have and use HSS, I am sure at some point I have broken both CS and HSS through my own fault. I might just give the spiral flute taps a go in the future, I hadn't realised that they would work as a hand tapping tool.

I had a quick look at Presto web site and they are asking to log in before seeing prices or buying taps or drills, do they only deal with companies or bulk orders?

[Anonymous]

I mostly tap dry. If lubrication is needed I use Rocol RTD; mostly on difficult materials like stainless steel and/or bigger taps, say 3/4" upwards. The RTD goo works well, but is a PITA to remove from tap and hole. On aluminium alloy I sometimes use WD40 just to stop the swarf sticking to the tap.

As for drill sizes i usually aim for a thread depth of 60-70%. In tough materials I'll be nearer 50%. For fine pitch threads I aim for 70-80% engagement.

If an internal thread is screwcut I go for 100% thread depth.

Some years ago I did some experiments on thread depth. Material was 6082 combined with a high tensile (12.9 grade) SHCS. The bolt fractured before the internal thread stripped with 50% engagement; I didn't bother testing the higher engagement percentages.

Andrew

[JasonBModerator @jasonb]

I tend to stick with the diameter less pitch for metric a sit was what I was first taught particularly if the hole is shallow, I may go a bit larger on some thing that does not need any strength such a a screw holding parts in place that are going to be silver soldered – easier to tap and less ware on the tool. As I tend to drill in the mill it is easy to also use that to guide the tap while turning it by hand

I've a mix of both CS and HSS, tend to get CS for odd sizes that I wont use much but the commonly used ones are generally HSS both hand taps (Dormer E500 series) and the ones that I tend to reach for most often now are Spiral flute (mostly YG-1 general Purpose Combi Taps). I do have a few spiral point but don't see the need for both Spiral point and spiral flute for non production work as the spiral flute will still eject the swarf from a through hole as well as a blind one. Few spiral flute and a hand tap being powered by the SX2.7 below, details of taps if you view direct in youtube. I'm using The Rock oils monkey juice that ARC sell in the video but also use CT-90.

 

J

 

PS I did a similar test to Andrew and got the opposite result – a stripped thread in the hole and was even using a cheap ungraded bolt

Edited By JasonB on 22/05/2019 16:40:26

[AdrianRParticipant @adrianr18614]

I just moved some more things from my old house to here. I found that I have a brand new set of Halfords taps and dies. Havnt a clue where it came from, but along with the Sherwood STP I just bought they cut the threads almost as easy as screwing a bolt in.

I also discovered that my old place was 1 mile from Cromwell tools. It must be the last bastion of storemen. Dont get me wrong they were totally polite and helpful. Just I got that feeling that I was only allowed in if I did not touch anything.

I asked for a 500g tub of Rocol RTD. He did glance at the terminal but did not touch it. I could see the contempt in his eye for automated stock systems. Of he stalks into the depths of the racking, a while later he returns with a bottle of Rocol RTD oil. I stick to my guns, and say "no the one in a tub". Of he goes again, a bit longer this time. He returns empty handed. Well I am prepared for this, I have the power of the Internet and have already looked up what they sell. What about Trefolex I say, and of he goes again. Even longer this time, more muffled thuds and scrapes and he returns with Sherwood STP and says what about this? I decided tweaking the tail of sleeping tigers is a bad hobby and agreed, yes that is perfect. I even got a smile which rapidly turned to a scowl as he aproached the terminal to make the sale.

[SillyOldDufferModerator @sillyoldduffer]

Posted by AdrianR on 24/05/2019 14:50:59:

…

I also discovered that my old place was 1 mile from Cromwell tools. It must be the last bastion of storemen. Dont get me wrong they were totally polite and helpful. Just I got that feeling that I was only allowed in if I did not touch anything.

…

My local metal vendor is like that too! I got on much better once it was established I knew what I wanted and was going to spend a decent amount of cash.

Having watched other customers while waiting for metal to be cut, I started to sympathise with the staff's off-putting attitude. Rather too many of the public arrive seeking free advice on all things metal related, or die of shock when told the cost, or otherwise dither and waste time. Much better to be the kind of customer who knows what he wants, can discuss alternatives, and then pays up cheerfully.

Last time I was in an elderly chap (ie a gent slightly older than me) was most concerned to explain why all new steel is, I quote, "crap". He lectured the assistant for about 10 minutes until he realised the queue behind was annoyed at which point he left without buying anything! I wish I'd thought to recommend the forum, what he said was misplaced in a busy shop but would have made an interesting post – his views were based on professional experience.

Dave

[Raymond AndersonParticipant @raymondanderson34407]

Castrol Variocut is a superb tapping compound very economical and easy to clean, results in very nice threads. I have about a litre left and I think it is possibly not available in UK now . As for taps /dies I much prefer HSS to CS, Emuge Franken being by far the best taps I have used [ they don't do Dies ] Dies… I would say Walter, I also have Dormer, OSG and Guhring any of those makes will give long service.

[Author]

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