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Carbon Steel vs HSS Taps & Dies

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PaulR27/11/2016 22:18:28
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This must have been discussed before but searching for 'carbon steel' on the forum doesn't throw out any relevant results - Google gives plenty or results but opinion seems divided (as ever!). I need at least 4 different BA taps/dies (in the range 4BA-9BA) to build my project but need to watch the pennies - looks like buying HSS as required will cost about £10 per tap/die pair whereas a set of 0-9 in carbon steel can be had for just over £50 (inc holders etc). I've also had a good look on eBay but the chances of ending up with a pig in a poke seem a bit too high.

So what do you think about carbon steel? I'm going to be using BMS, brass and cast iron.

not done it yet27/11/2016 22:55:40
6812 forum posts
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Search for 'taps' and choose any relevant thread?

Andy Ash27/11/2016 23:28:02
136 forum posts
33 photos

You'll be fine with carbon steel.

HSS maintains temper at elevated temperature..... Just don't be power tapping into 316 stainless.

Really decent HSS taps and dies (skf,dormer,presto,clarkson,osborn,europa etc) are much better, but mainly because more attention has been put into the grind.

Properly ground tools are better no matter carbon or HSS.

Watch out for badly ground taps and dies. Often you will find that cheap carbon taps and dies have barely been ground. Sometimes you can even improve them yourself with a Dremel. I'd say that's a last resort though.

Really cheap taps and dies from China can be unusable, so watch out for those. Usually they come in sets but the button dies aren't split. There's nothing wrong with dienuts as such, but if you see a set where you would expect split dies and they aren't. Give it a wide berth.

Generally you get what you pay for.

P.S. Older is sometimes better. Older taps and dies were often just made better than their modern carbon steel brothers. If they're not actually worn, you might find old, second or third hand, is better than brand new. - Especially in imperial sizes.

Edited By Andy Ash on 27/11/2016 23:31:47

Frances IoM27/11/2016 23:41:22
1268 forum posts
28 photos
the old rule was try to keep one set purely for use on brass and never use it in steel - think this esp true of carbon steel taps/dies.

also try asking around in your local model engineering soc - BA and other older taps/dies (usually Imperial) often surface in rummage sales or possibly another member may have some spares
steve de2428/11/2016 00:40:03
71 forum posts

PaulR,

If you already have similar diameter taps but they are metric or UN then usually it is ok to substitute those in whatever you are making. (That's the cheapest option!). There is nothing 'special' about BA threads, it probably just means that the original designer was British - if he'd been American they'd be UN threads, if continental then the drawing would call for metric threads.

I have always used carbon taps and get them from Tracy Tools (usual disclaimer) and so far been successful - I'm touching wood as I write this because I don't like tempting fate!

With these small size taps I always use the slightly larger tapping drill size as recommended by Tubal Cain to reduce the torque required to drive the tap at the expense of a slightly reduced thread strength.

I centre drill, drill, and tap without changing the position of the component under the drill press or mill - that way the tap is in line with the hole. I also support the non-working end of the tap either as a sliding fit in the drill chuck - or in a tube held in the drill chuck. Doing that stops any bending of the tap which I'm sure is the easiest way to snap a tap. I use a small (3 inch) tap wrench which grips the shank of the tap - gives me more 'feel'. And always use a tapping lubricant.

Hope this helps,

Steve

Chris Evans 628/11/2016 07:32:16
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2057 forum posts

OK I will blow against the wind, as a toolmaker for 50 years and still messing around in retirement I will only buy HSS. I have only ever bought a couple of carbon taps in really odd use them once only sizes in brass or aluminium.

I have no confidence in using carbon taps that could easily snap and ruin hours of work for the sake of saving a little money. I do have access to a spark erosion machine to remove broken taps but would rather not take the risk.

Ian S C28/11/2016 08:37:09
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7468 forum posts
230 photos

I to use HSS taps, until I needed a BA tap, even a carbon steel one cost over $NZ 30, HSS was nearer to $NZ 50.

Ian S C

Bob Rodgerson28/11/2016 08:43:21
611 forum posts
174 photos

I have almost always chosen to use Carbon Steel taps and dies and have found them no worse than HSS taps & dies. I was glad that I had chosen Carbon Steel recently when I broke a tap and had to drill it out using a carbide end mill.

Danny M2Z28/11/2016 10:28:25
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963 forum posts
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Carbon steel tools are fine for taps and dies.

Your favourite file may be made from carbon steel.

Come to think of it I cannot locate any HSS files online. Do they exist?

dont know

Tony Pratt 128/11/2016 11:39:39
1967 forum posts
12 photos
Posted by Chris Evans 6 on 28/11/2016 07:32:16:

OK I will blow against the wind, as a toolmaker for 50 years and still messing around in retirement I will only buy HSS. I have only ever bought a couple of carbon taps in really odd use them once only sizes in brass or aluminium.

I have no confidence in using carbon taps that could easily snap and ruin hours of work for the sake of saving a little money. I do have access to a spark erosion machine to remove broken taps but would rather not take the risk.

Hi Chris,

Not blowing in the wind, I concur with you sentiments also from half a lifetime in Toolmaking. I will say that carbon steel taps obviously do work but from my home shop experience the quality is not good, generally the threads are machined then hardened & then the flutes are ground, HSS steel taps are ground all over after heat treat.

You pay your money & gets your choice.

Tony

Circlip28/11/2016 11:41:32
1510 forum posts

Carbon steel dissolves quicker than HSS when subjected to the Alum treatment.

Regards Ian.

SillyOldDuffer28/11/2016 11:44:28
Moderator
8699 forum posts
1967 photos
Posted by Danny M2Z on 28/11/2016 10:28:25:

Carbon steel tools are fine for taps and dies.

Your favourite file may be made from carbon steel.

Come to think of it I cannot locate any HSS files online. Do they exist?

dont know

As a metal cutting tool material Carbon steel has one huge disadvantage. It loses hardness when it gets hot and goes blunt, perhaps at temperatures as low as 120C. As its other properties are suitable Carbon Steel is a good choice for hand tools (like files) because they are unlikely to get very hot.

Tool bits in a machine are a different matter, They can easily get much hotter than 120C. Flood cooling and light cuts help, but commercial productivity is low whenever Carbon Steel tooling is used. Manufacturing was revolutionised by HSS because it remains hard up to red-heat temperatures, and carbide has even better heat performance.

For amateur use speed doesn't matter as much. Carbon steel can be made sharper than HSS, which in turn is sharper than carbide. And for many purposes sharpness may be more desirable than cutting speed.

Dave

Edited By SillyOldDuffer on 28/11/2016 11:45:22

MW28/11/2016 11:59:01
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2051 forum posts
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You'll be fine using carbon steel on a vast array of materials, obviously with the harder ones you'll get some longevity out of a HSS over a carbon steel one, but thats only if you're certain you'll need it only for harder materials, otherwise a very very large amount of carbon steel variety tools will be good to take advantage of.

Michael W

Nigel McBurney 128/11/2016 12:39:07
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1000 forum posts
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Fifty or sixty years ago British carbon steel taps and dies were very good,at work (instrument making) most of the BA and brass thread taps/ dies were carbon steel and in brass ,cast iron and aluminium they would tap hundreds of holes without trouble,we never did much production tapping in steel. I can understand in toolmaking where the value of the workpiece is very high ,the use of ground thread HSS taps and dies being justified due to the tough toolmaking steels and the risk of expensive scrap, though HSS tools in those day were very expensive. Initially I bought carbon taps for model making and they were good ,since then I have acquired a lot of used HSS tooling from tool dealers,boot sales auto jumbles,job lots at auctions,modern carbon taps and dies are definitely not as good ,poorly made,tending to jam in the holes etc though a lot cheaper particularly if a tap is only required for a one off,which happens when working on vintage restoration. If making new models why not use metric, just because a drawing says tap 5 BA use some judgement and use 3mm,and similar with other sizes ,metric HSS tooling is readily available and no doubt cheaper.I can never understand how some so called experienced persons ever come up with the BA system,silly rounded threads with odd angle and ridiculous pitches.

PaulR28/11/2016 13:13:55
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123 forum posts
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Thanks for all the input. I should say that this is my second stint of model engineering (I got frustrated and sold most of my stuff about 5 years ago but have just acquired a 'new' 1972 vintage lathe) so I'm ok with the mechanics of tapping/threading and not bothered about mixing units, I'm just having to buy a shed-load (well, garage-load) of gear in one go to get underway again.

Last time 'round I used metric HSS and whilst a total noob managed to break a 3mm tap but that was the only breakage I suffered. I bought various HSS BA sizes as and when required and still have quite a lot of screws etc that I didn't sell, so I 'd like to be able to use these. I'm likely to be needing threads in the 2-6mm range but there don't seem to be any metric sets that cover this, they seem to be in sets of 3mm+ or 1- 3mm (half of which I wouldn't use). So a BA set of 0-10 would cover the required size range, provide the holders etc that I also need and enable me to use my stock of screws. Hmmm, I've convinced myself: carbon BA set it is.

If I start breaking them, I'll blame you HSS-only guys for not haranguing me hard enough :P

Thanks again,

Paul

 

 

Edited By PaulR on 28/11/2016 13:15:21

Mike Poole28/11/2016 13:17:27
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There is no reason why a carbon steel tap should not be made to the highest quality but as it is relatively cheap compared to HSS the cheap end of the market will use carbon steel and has earned carbon steel a reputation for poor quality. The problem is that some poor quality taps are made of HSS so it is not a guarantee of quality. So we are down to choosing brand names of known quality or buying from a reliable supplier of imported Asian equipment. A reputable supplier will stand by his product and take some care in the selection of his stock. The cheapest is seldom the best but some of the major brands offer a performance that far exceeds what most hobbyists need, I feel there is a middle ground of a well made tool at an affordable price. Generally the major brands will not disappoint but they can hit the pocket hard. I have some good quality sets of carbon steel but if I need to replace any I choose HSS so this gives me the usefulness of having the right size but my most used sizes get upgraded to HSS ground thread taps.

Mike

PaulR28/11/2016 15:04:53
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Thanks Mike, that's pretty much the strategy I have in mind.

Tim Stevens28/11/2016 22:04:28
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1598 forum posts

The cost of BA taps is likely to be more than for standard metric - but not hugely so. On the other hand, supplies of BA screws are likely to be twice the price or more, and harder to find. In my UK experience.

Cheers, Tim

PaulR28/11/2016 22:13:10
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123 forum posts
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Thanks Tim, I guess that's something else I should throw into the mix.

Hopper29/11/2016 02:33:08
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6421 forum posts
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I have found over the years that you have to try a lot harder to break a good quality HSS tap off in the job than a similar quality carbon steel. But the cost factor is significant these days.

Whichever way you decide, pay the money for a good quality brand of taps and dies. The cheap ones, even cheap HSS, can result in horror stories.

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