"Mike" wrote in message
ps.com...

dcbwhaley wrote:
Any advice on buying taps. I need sizes from 2.5mm to 6mm (including
3.5 mm - even though my local DIY shop tells me metric screws only come
in whole numbers) for tapping mainly aluminium and occassionally mild
steel.

MY internet search seems to find huge sets of taps and dies at
suspiciously low prices or individul items at pocket wrecking prices.
Materials seem to be carbon steel, tungsten steel and high speed steel.
Which is best?

Dave
Hi Dave
for aluminium carbon taps will be a lot cheaper and will work fine for
the occassional mild steel. Just remember the tapping size hole to give
a 60% to 80% thread engagement. Try some of the model engineering suppy
firms.

The problem with carbon steel is not the material but the manufacture. From
a known name manufacturer a carbon steel tap would be fine but unfortunately
the cheap sets vary from ok to useless. Good manufacturers tend to use HSS
because the extra material cost makes little difference to the final price.
The Hertel and Lyndon taps from J&L are only £2 to £5 each in the sizes the
OP wants so they aren't going to break the bank. You can manage with just
2nd (plug) taps for most work rather than having to buy all three per size.

The alternative is somewhere like Sert Tools near Slough for second hand
taps if you are prepared to rake through their boxes to find what you want.
You can pick up as-new top quality taps like Dormer for a quid each. I go
there every now and then with my list of missing sizes and spend an hour or
two going through their boxes of taps, dies, reamers, drills etc.
--
Dave Baker
www.pumaracing.co.uk
"Why," said Ford squatting down beside him and shivering, "are you lying
face down in the dust?"
"It's a very effective way of being wretched," said Marvin.