On Mon, 12 Jun 2006 20:25:20 +0100, "Simon"
wrote:

I'd like to create a few M4 or M5 threaded holes in some pieces of brass and
aluminium that I've got.

Is buying a cheap set such as
http://www.screwfix.com/app/sfd/cat/...12080&ts=39681 in order to
gain experience a good plan?

Probably not - certainly not if you know the sizes beforehand and you
only need a couple of sizes.

It _might_ be useful for Gross Bodgery if things come into the workshop
where you never know what size you'll be needing next. OTOH, the
Screwfix ones are really bad quality and they're metric only. M12 in
carbon steel ? The thing is going to last about an inch, if that much.

Are the eye-wateringly expensive sets that RS sell necessary for DIY use?

Yes. Although you can get them for less than RS' prices.

The simple rules for taps and dies:

Are you now, or have you ever been, a reader of Model Engineer? if you
haven't, then you only need a couple of sets of metrics and you're
sorted forever. You can afford these, even in good quality.

HSS. Carbon steel is a bad joke.

Presto, or similar quality, and made in England (or Europe at least).
Don't waste your time and metal on cheapies.

Almost any amount of effort to avoid breaking a tap is easier than the
trouble of removing a broken one.

Taps. You need taps, not often do you need dies. People without lathes
very rarely need dies.

Taps come in sets of 3 (taper, second, plug), not sets of 2. Real ones,
that is. For small taps then you can manage with only second and plug
quite adequately (no taper) but the 2-tap sets are often somewhere
between "taper-second" and "chamfered plug".

2 fluted taps will break if you bend them sideways. Nearly all very
small taps will be 2 fluted, but get 3 fluted if you possibly can.

Dies are adjustable in size. Set them correctly, or you'll have loose /
tight threads.

A set of Zeus tables is useful, but you can often pick up freebie
equivalents in better toolshop.

There are two metric pitches (for most threads).

Tapping drills are magic sizes. Now drills are cheap, so buy extra
tapping drills just the right size when you get your taps. Keep them
with the taps and don't use them for anything else.

Get a nice tap wrench. Get several, of different sizes. eBay.

Get a squirt bottle of RTD (cutting goop) if you ever tap steel. If
without, then at least use _something_ greasy or oil. Brass often needs
cutting lube to clear the chips away too (back the tap out and wipe it).

Use the right tapping action - two flutes forward, one flute back.
Pretty spirals look nice, but they'll bind and break your tap.

Spiral taps make a great bargain at an auction, but they're machine taps
and there's a reason why few people buy a second one for hand use.

A tapping machine is very useful, especially for fine work in aluminium.
Use a drill press with the belt off and maybe the feed spring unhooked,
at least until you have the thread started square.

If you use the same size over and over, then keep spares on hand.
Particularly M3 !