I have lots of taps and dies but kept finding that I needed metric at times so bought odd quality ones as needed. Became a bit fed up with this so bought a seft of screwfix. This one
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It wont be super precision. That would cost a great deal of money. The set has changed since I bought mine. They were split dies with a screw in each one for adjustment that doesn't work out too well. I believe this was favoured in Japan. It was also in a wooden box. It's pretty good value. Depending on what you want to make there may be a need to add a few smaller sizes. I had one problem with the set I bought. One of the small dies was incorrectly marked – it was smaller than the indicated size. I'd guess this is rare. I could have spotted that by seeing if the tapping drill looked to be correct for it. Depending on standards it may not actually go in.
The carbon steel sets can be very mixed. I've had no luck at all with the cheap ones but only tried UN types which I hardly ever use anyway. The set I bought was useless even though it was dearer than some.
For BA and ME I feel it's better to buy used especially ME. Some times Triangle brand sets and others in a wooden box crop up on ebay. They are ok and marked stocks and dies for some reason or the other. They tend to be mixed 40 tpi with brass tpi in in larger sizes.
I would be inclined to forget metric fine as the normal pitch is available in a large range of sizes right down to very small. It might be of use at very small sizes say circa 1 to 1.5mm.
One other aspect – is there a need for the imperial threads at all? Mostly no as they can be replaced with a metric equivalent . If something calls for say 1/4 BSF there will be no problems replacing it with M6. If something calls for 10 BA it could be replaced with M1.6, even the pitch is near identical. This means that both imperial designs with slight size changes in places can be made using the same taps and dies as metric designs. This is the full range of metric coarse
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Problems come when something has to be made to fit something that uses BS or UN threads where it's to be fixed to the part. Also 40tpi was a favourite for adjustments as it's the same as a mic spindle. That isn't well covered by metric threads as a 0.5mm pitch would be needed for the same sort of use if it was a micrometer spindle for instance. 40tpi 1/2 dia isn't a problem. 0.5mm pitch isn't so easy but there are taps about in several sizes.
No idea what the price is now but RSComponets do a very good left hand metric tap set at a very reasonable price. Pity that the dies are rather expensive. When I bought mine the cost of the set was little different to what some were charging for one tap, less in some cases. Dies – just buy as needed but split ones will work out at £20 each at the good cheap end.
John
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