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BA, ME, Metric Coarse or Imperial : which taps and dies to buy ?

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Brian John11/04/2014 05:48:11
1455 forum posts
579 photos

I am new to model engineering and I am wondering what nuts, bolts, taps and dies most people use when building model stationary steam engines. Is it BA, ME, Metric Coarse or Imperial ? Are there a few sizes which keep cropping up ?

Bob Perkins11/04/2014 07:25:28
249 forum posts
60 photos

Hi Brian

when I started a couple if years ago I bought what I needed when I needed them. I have built a collection of tapa and dies I use all the time now. If I had bought sets there would be many unused. I adopted the same strategy for reamers and milling cutters. The only set I don't regret buying was a comprehensive set of drills

JasonB11/04/2014 07:32:12
18593 forum posts
2046 photos
1 articles

I think the best thing to do is look a a few engines that you think you are likely to want to build and see what they use, for example if you want to do some of the Stuart range then they will use BA fixings and a few ME sizes on pipe fitings etc. On the other hand if you like the look of Anthony Mounts engines then these are generally in metric but can have BA fixings and a finer ME pitch than Stuarts on their steam fittings. If its the European designs then metric fine pitch would be the way to go. American designs mostly use UNC with a bit of UNF

From the above you can see there is no real system that suits all subjects so probably best to buy the individual taps & dies as needed rather than sets that will contain ones you may never use.

You can of course substitute whatever thread form you like but need to follow that through on the whole engine, for example if the original design had say a 5BA thread on teh end of a rod and you wanted to go all metric then the nearest thread would be M3 but really you should also change the rod to a smaller 3mm one and any holes that rod passes through to suit.

tractionengine4211/04/2014 07:53:10
376 forum posts
109 photos


It's worth investing in good quality taps and dies. I have found that the quality of ME taps and dies in carbon steel is generally poor and I have had difficulties getting good fitting threads using these. I no longer waste my time using these.

As a result I now only buy good quality HSS taps and dies, To keep my cost down I try to stay with UNF, and on larger sizes UNEF, for fine threads and BA for small threads. For general use I use metric course. Metric fine would be a good alternative to UNF.

Mostly I am using 10 to 0 BA sizes, UNF 1/4" to 3/4" and UNEF 3/8" to 3/4" and rarely use anything else. Where metric or ME sizes are specified I will substitute with these.

I find by sticking to this philosophy good quality brand tools can be bought at relatively good prices.

Maybe others have had better experiences with ME taps and dies and can recommend a good quality source at reasonable prices.



FYI here's UNEF thread range which I find very useful.

Edited By tractionengine42 on 11/04/2014 08:02:45

Robbo11/04/2014 10:08:23
1504 forum posts
142 photos

I would say wait and buy them as you need them. Go for quality HSS rather than carbon. A reliable source is Tracy Tools, and they send them quickly so you won't have to wait long to tap that thread!

Brian John11/04/2014 10:44:16
1455 forum posts
579 photos

I have already bought carbon steel ME taps for the 1/8-40, 3/16-40 and 1/4-40 (Tracy Tools) but these will be used on copper and brass for pipe work and boilers so they should be okay for that.

I will follow the above advice and just buy what is needed and only buy HSS taps and dies from now on. Thanks.

JA11/04/2014 10:46:51
957 forum posts
52 photos

Buy the best you can afford when you need them. This also applies to reamers, end mills and slot cutters. Mistrust any vendor that sells you a tap, die etc loose (not in a protective case). Never buy on impulse.

Generally I have found Chronos's dies, taps etc excellent quality, both carbon and high speed steel, and their service good.


Roderick Jenkins11/04/2014 11:49:36
1924 forum posts
503 photos

Carbon steel taps and dies are just as hard or harder than HSS. For hand tapping the only advantage of HSS is that it is generally tougher so you are less likely to break a tap in the smaller sizes. The major cause of tap breakage is probably using too high a percentage of engagement. Use Tubal Cains' recommendations for tapping size drills and you can pretty much eliminate tap breakages. Using a tapping guide like the Universal Pillar Tool also helps and will allow you to use the carbon steel versions, with a considerable price advantage. In my opinion HSS is not the wonder metal some people make it out to be. It's advantage over carbon steel is that you can get it to red hot without softening: so great for lathe tools and milling cutters. For taps and dies - not a major plus point to the model engineer.

I've had a lot of carbon steel taps and dies from Tracy Tools and have found them perfectly satisfactory.

Just my tuppenceworth,


Chris Parsons11/04/2014 11:56:29
118 forum posts
37 photos

I would also give a thumbs up for Tracy Tools (they are local to me which is also pretty convenient)

I started a year or so ago and decided to 'go metric' as this is what my lathe and mill were, but have bought many other odd (ME and BA mainly) taps and dies since as and when the need came up.

I originally went for a boxed set of metric taps and dies (2- 10mm) which got me going but would agree that they get blunt quickly and most of the commonly used sizes have been replaced by HSS ones from Tracy - but this does mean you have a convenient box to keep the various sizes in, which I am starting to find is a problem with the others - rummage through the drawer and the one you want is always the last one you pick up...

As someone has mentioned you can get HSS boxed sets but they are a few quid and you may end up with ones you never use


John Alexander Stewart11/04/2014 12:00:01
772 forum posts
52 photos


Not knowing where you are, for me, overseas, BA is a non-starter. Kirk Burwell of Hemingway Kits no longer supplies BA with his kits, because getting quality fasteners is tough. (read it in full on his web site)

You may wish to use metric; that's what I do. Most others here use UNC/UNF, but I think in the long run, metric will win out.

When I started out, I, too, purchased a set of ME taps and dies from Tracy tools, but I did have issues getting threads to fit, and slowly, the Tracy ones were replaced. Now, I use metric fine - and I get the taps and dies from a tooling supplier; maybe a lot of money for a tap set, but, you might as well purchase the best.

(The Tracy Tools set were a "life saver" - not putting them down in any way, but now I just purchase what I need)

Another JohnS. Blog: **LINK**

Brian John11/04/2014 13:54:26
1455 forum posts
579 photos

I live in Cairns, Australia and I purchase from both the UK and the US.

Martin Walsh 111/04/2014 14:09:42
113 forum posts
2 photos

The hss v carbon taps and die debate has been going on for quite a while

I personally buy carbon steel taps and dies for 2 reasons 1 they are quite a lot cheaper than hss

and 2 for cutting threads by hand there is no real advantage using hss

hss is only better if you cut threads under power

I buy my taps and dies from the tap and die company

Although they are manufactured in India they have got the most modern factory

and equipment to make them.

Best Wishes Martin

John Alexander Stewart11/04/2014 14:10:44
772 forum posts
52 photos
Posted by Brian John on 11/04/2014 13:54:26:

I live in Cairns, Australia and I purchase from both the UK and the US.


I got my start in metric when living in NZ back 1990 timeframe - became fully metricated shortly after that when living in continental Europe.

I could be wrong, but I'd think metric would be easiest?

I'm currently building a Martin Evans' designed locomotive, "Ivatt", and I convert to metric and write things down on the drawings and/or in a notebook. All fasteners (well, except the 8BA threaded handrail stanchions I purchased ready-made) are metric.

I do have trouble purchasing metric dimensioned stock, but as much of what you do leaves little of the original stock showing, so what?

Anyway, I'm having fun with this build, just need more time in the workshop...

John from Canada.

Martin Walsh 111/04/2014 14:11:05
113 forum posts
2 photos
Posted by Martin Walsh 1 on 11/04/2014 14:09:42:

The hss v carbon taps and die debate has been going on for quite a while

I personally buy carbon steel taps and dies for 2 reasons 1 they are quite a lot cheaper than hss

and 2 for cutting threads by hand there is no real advantage using hss

hss is only better if you cut threads under power

I buy my taps and dies from the tap and die company

Although they are manufactured in India they have got the most modern factory

and equipment to make them and they are top quality

Best Wishes Martin

Bob Youldon11/04/2014 14:30:37
183 forum posts
20 photos

I have to agree with those who have said buy whatever you require at the time and I can also concur carbon taps and dies are perfectly adequate for general model engineering, just use the right cutting fluids/ pastes where necessary. I have recently succumbed to replacing one of my 6BA taps I purchased when first starting out. . . . . more than sixty years ago!


Bob Youldon.

Steve Withnell11/04/2014 19:23:21
815 forum posts
217 photos

My practice has been to buy taps and dies to suit what ever I'm working on and only when I need them. It can be more expensive on a one off basis, but cheaper compared to a full sets of which only a couple ever get used.

The issue about HSS v Carbon Steel isn't so much about the material itself, it's just that there are a lot more junk taps/dies about made from Carbon Steel - my opinion, so if you buy carbon steel, you do need to be particularly careful about the quality/sourcing. A quality HSS tap will always be better than a junk carbon steel tap.


Bill Pudney12/04/2014 03:34:29
459 forum posts
16 photos

I buy taps and dies as I need them. Having bought a few carbon steel taps/dies early on in my journey, and being burn't every time I now buy HSS/ground thread irrespective.

The problem I have found is burrs left by the milling of the flutes, Most of the threads I generate are in al. alloy and fairly fine pitch, usually under 1.0mm. Sometimes the burrs on carbon steel taps and dies completely changes the thread form, to the extent that some "threads" formed resemble a vague squiggly helical groove rather than a thread form. Whereas all the ground thread taps I have, and there are quite a lot, are burr free. Now obviously on a M12 x 1.5 tap any burrs will be relatively smaller than the burrs on my fairly small carbon taps, and its possible that tapping harder material may remove some burrs.

Wherever possible I drill and tap either in the lathe or the mill, so alignment is assured. Also, I almost always use hand power rather than tapping under power. Some good tapping fluid is a good idea as well. For what It's worth if the right size tapping drill has been used, I believe that most taps are broken by being misaligned. Hence my use of the mill or lathe.

Just check your taps and dies with a good loupe in a good light.



Brian John12/04/2014 04:55:01
1455 forum posts
579 photos

I will not be tapping under power. It is my intention to tap in my Sieg C2 lathe, turning it by hand. But I have to get it set up first ; it is still sittting in the box on the floor. It is much heavier than I thought it would be ! My first lathe job will be to make a spindle handle so that I can turn the lathe by hand for tapping. I thought all lathes came with a spindle handle as it seems such a useful accessory.

I will buy my taps from either Tracy Tools or Chronos Engineering.

What is the verb for using a die ?



Edited By Brian John on 12/04/2014 04:55:45

Edited By Brian John on 12/04/2014 04:57:08

JA12/04/2014 07:58:22
957 forum posts
52 photos

To die.


Rik Shaw12/04/2014 09:07:36
1352 forum posts
368 photos

Using a die? - To thread, I thread, you thread they thread, we all thread (that is of course when we are not wasting time at these blessed keyboards)wink 2

Of taps and dies? I have collected hundreds over the years - both metric and imperial - whitworh, bsf, unf, unc, ba, bicycle, gas - you name it! Two things though - I have NEVER paid full price from a dealer and I only use HSS. Avoid cheap carbon steel unless you regularly tap/thread cheese.


Motto: Everything comes to 'im as waits!

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