Why are BA taps so blooming expensive??

I’ve just started building my first steam engine, a Stuart S-50.
I’ve got loads of metric and BSW taps and dies but no BA ones so tonight went on a little shopping expedition.
WOW!!!

Is it just me, or is a set of decent HSS 7BA taps really dear in comparison to other possibly more normal thread forms. £40 for a set of 3 Presto taps!

Thats sure going to up the cost of this build

Jim

I've just bought a set of even taps and dies 0 to 10 BA from Tracy tools with postage and VAT came to what you just paid. They are not HSS but carbide but I'm sure they will last me out.

Chronos Engineering have a HSS 7BA set of 3 advertised for £18.50

Paul.

.

7BA was never a common size, Jim

... I think you may have “jumped in at the deep end”

MichaelG.

Add the fact that they are just about obsolete in industry so are only made in small batches for the ME users which will put the price up.

Try our "Cherished suppliers" - TracyTools. You will be pleasantly surprised. Also, I rarely use a second tap, just taper and plug. Why HSS ? Carbon Steel for the most part will give you good cutting and life etc at £1.50 a tap. However, I do prefer HSS dies.

Bob

Carbon steel taps are perfectly fine for model engineering. I've got lots of them, mostly from Tracy tools but Proops on eBay are cheap and ok. If you want a bit better quality RDG [myford] are good value. I've got them from china too and they are a bit of a lottery but cheap.

Avon tap & die are good too

www.avontapdie.co.uk

Odd numbers in BA were never popular in industry. At least they weren't where I worked. And Stuart Turner often used a lot of odd sizes for lots of things like crank shaft bearings, crank pins etc  

Roy

Edited By roy entwistle on 21/09/2020 09:01:55

The Tap & Die Company are long established with impressive customer list and NOT expensive

https://www.tap-die.com/contents/en-uk/d148_BA_taps.html

Maybe because nobody bothers with them anymore, so not many being made.

Jim,

I know you have bought your taps now so I may be hounded out as a heretic by suggesting that near metric equivalents would be every bit as suitable; they are readily available and at sensible cost

JasonB pointed out that BA taps and dies are obsolete and made mainly for ME buyers at a premium price. As an example M3 at 0.5 mm pitch compares well to 7 BA at 0.480 mm pitch and to me it does seem like a rather expensive way of sticking to a drawing requirement just for the sake of it.

Brian

.

’though it is, of course, over-size on diameter

This may, or may not, cause difficulty on the S-50 build ... I don’t know.

M2.5 would perhaps have been convenient [?]

MichaelG.

Brian has made a valid point which I was about to query - why insist on the 'design' values? I would suggest that these miniature engines were not designed to that degree and were the product of 'most available'.You aren't making interchangeable components, so adapt to something similar. Given my lack of expertise in this area, I'm possibly missing something ... but what?

rgds

Bill

Agree with Michael M2.5 is a better alternative to 7BA, both will cut a usable thread on off the shelf 3/32" stock. Save M3 for when you want to substitute for 5BA.

As The Stuart engines are supplied with all barstock, nuts and bolts/screws and the usual builder is a beginner they probably lack the knowledge or experience to make substitutes and also don't want to discard the supplied materials and fixings. Would be a different matter if the kit were just castings and no materials.

Pre metric, 5 & 7 BA, although non-preferred are 1/8" & 3/32" resp. so, for scale purists, they do nicely for imperial sized fasteners for, say, 1" &1.5" to the foot models. Hughes' Allchin for example makes extensive use of them.

In the smaller sizes, the BA range offers a slightly more graduated range of diameters than metric standard, which can be useful.

The ME trade doesn't seem to offer metric fasteners with one-size smaller hexagon heads as widely as they do for BA sizes, which makes for a neater appearance

Hi all and thanks for all the valuable insights.

I would be most happy to change the fixings to metric, as long as I could retain the hex headed fasteners, especially as I haven't yet bought the BA taps and dies. I have drilled the base plate for the cross slide guide to be tapped 7BA - hopefully this will translate to M2.5 OK.

I don't mind replacing the grub screws for hex headed ones - in fact that's a bonus to my mind.

Is there a good source of small metric bolts with correctly sized hexagon heads?

Many thanks,
Jim

Polly Engineering in the UK do the small hex ones in a limited range or you can get the full range from GHW in Germany which is who I usually buy them from.

2.1mm hole will be Ok for M2.5

Edited By JasonB on 21/09/2020 13:05:59

Like you I had the same issues & even now that I have a decent set of BA tap I tend to substitute with M2.5 & M3 where feasable, much cheaper, & much more easily obtainable nuts, bolts, half nuts, hex head, cap screws, etc.

George.

Edited By mechman48 on 21/09/2020 13:44:34

Anyone watch the Spitfire Factory last night?

Required a 2BA socket to drive bolts holding the tail plane assembly onto the fuselage

Edited By KWIL on 29/09/2020 11:14:02