Fiddling around practicing to become a model engineer and
having now mastered cutting and filing bits of metal my next stage is to do
some tap and die cutting.
Now what sort of metals do I need to make nuts and bolts.
and what tap and die set should I get?
I need some mini ones for ME and a big set up to 10mm for my Stationary
and other bits and bobs.
I have a budget of £120.00
Model Engineers use 40TPI threads for scale appearance.
Other than that, BSW and BSF will be useful, Metric and UNC/UNF threads are of
limited use in your environment.
Peter & Rita Forbes
If you are tapping blind holes the set of three (taper, second and
plug) is useful - the taper tap is a must for starting a thread in a
hole as it both guides the tap to enter straight, and doesn't offer
too much initial resistance - if only contemplating nuts a taper tap
will form a full thread provided the nut isn't too thick.
The use of a lubricant such as Trefolex is beneficial when cutting
threads with taps and dies.
The Workshop Practice Series book on Drills, Taps and Dies offes much
information on this subject at resonable price.
Return E-mails to firstname.lastname@example.org
Tracey Tools is pretty expensive................the best place for a good
tap and die set is Ebay!
You can often get very high quality pro sets, s/h, that have been cleared
from engineering shops, at a lot less than the Chinese stuff you get new
The difference between fine and course is just that. for the same size
thread, fine will have more threads per inch than course. These may or
may not be within a standard series.
For tapping, a taper tap is essential. A plug tap is necessary when
tapping a blind hole. A second tap is nice but in'st essential.
Your best bet to learn all of this is to find someone who knows and
talk to them. There's little substitute for trying it yourself. Do
colleges still offer metalworking classes? If they do, try that. A
number of semi retired craftsment I knew used to teach evening classes.
Alternatively, find a club or organisation that specialises in old
machinery and talk to some members. Stationary engine, tractors and
vintage car clubs are freqently a good start.
Go and search uk.d-i-y This question has been asked and answered
well several times.
Taps are useful, thread-cleaning dies and thread-cleaning files are
useful, thread-cutting dies are nowhere near as handy. You just can't
practically make nuts and bolts yourself - you buy them. Nearly all
the thread cutting I do is tapping holes into big lumps or even thick
sheet to take a bolt. Turners might do a bit more thread cutting in the
lathe (a good place to do it). As a way of making threaded rod, then
it's just a better result if you roll form the thread (complicated
machine) rather than cutting it. Nuts aren't worth the trouble as you
can't hold them easily. Of course there are exceptions - brass nuts
don't seize on exhaust fittings and decorative brass fittings are
always handy. In general though, you'll be tapping holes, not using a
Threads come in different categories "coarse vs. fine" and "Brit vs.
Yank vs European" British coarse and fine were BSW (British Standard
Whitworth) and BSF (BS Fine). Yank were UNC and UNF (Unified). BSW kept
going for some years but BSF evaporated very rapidly after WW2 in
favour of Unified threads. I remember Dad scrapping literally wagon
loads of BSF tap and die sets - there was a vast pile of them at one
time, a couple of ton of unrusting steel sat in a corner of the yard.
If you need any of these, buy them S/H -- they're still around easily
As for a thread system to actually use, then go with metric. Buy
yourself top-grade Presto tap sets of three taps, as and when you need
them. As we no longer use so much low-grade cast iron, the metric
series de-emphasises the coarse thread standards and mainly uses a
single set of pitches.
Then there's the weird threads, like the 26tpi (threads per inch) brass
industry thread that used the same pitch for everything, because it
grew out of Victorian hand-chased threads cut on lathes with manual
toolrests. Also the range of tapered pipe fitting threads, electrical
BA threads (British through and through, but actually metric) and the
finickey 40tpi model engineering threads that tear up soon as look at
them. You're likely to encounter all these eventually, but don't rush
to buy expensive new tools.
You'll also need a Zeus pocket book to look up the size of the tapping
drill you should have used, but which you don't own and so had already
bodged without. But you need one of those anyway, just to fill out the
pocket of your brown dustcoat.
If I'm doing sheet, or soft materials like aluminium, then I usually
start with the second and not the taper. I don't need such a gradual
taper as I might for a deep hole in steel, and taking more of a "bite"
on each cut means I'm less likely to slip and damage it by accident -
easily done in ally sheet.
The right cutting compound (squirt bottle of RTD usually) and the right
back-and-forth action are also important.
As in UNF?
This would explain why even my (rather splendid)
local supplier couldn't supply 3/16 BSF bolts.
(web site down at the moment)
I needed them to repair a sliding patio door.
(eventually found at a double glazing company).
I also realised (browsing a thread table)
that 2BA is rather similar to 3/16 BSF
There are a number of threads at that size.
3/16BSF = 0.1875" x 32tpi
2BA = 0.1850" x 31.4tpi
M4.5 = 0.1772" x 33.87tpi
10UNF = 0.19 x 32tpi
3/16BSC = 0.1875" x 32tpi
3/16CEI is the same as 3/16BSC as the BSC series suceeded the CEI
For a modern structure, I suggest what you needed was M4.5
Yes. Take a look at some '50s or '60s ex-mil scrap / surplus. Chances
are you'll find a deliberate placard on it saying "This equipment uses
Unified threads". You might also see a series of adjacent circles
stamped down one face of a nut (particularly on pipe fittings) to note
I forget the details, but Whitworth and UNC either don't fit at all or
interwork quite well (camera tripod bushes). BSF / UNF OTOH are close
enough that a careless erk can easily gorrilate something by using the