Ive made an oddball tap / die set for a one off job, but that was in
I screwcut the tap, hardened/straw temper (silver steel) then ground
flutes with a dremel,
I then used it to tap the die from gauge plate, then split the die.
IIRC I hardened the die before I split it.
If gaugeplate will go hard enough I doubt you need to temper it much
Certainly do-able as my grandfather made his own scale taps and dies
for modelling, making the tap first and then the die to follow, and
all done with a lathe (including any milling) - when he made something
to scale then it REALLY was to scale! Sadly he has been dead for 40
years so I can't pry the secrets out of him, but I expect he was just
using high carbon tool steel, which can be made very hard just so long
as you don't warm it up in use, as can silver steel. If you want to
tap at commercial speeds then it a bit more tricky.
On or around Sat, 03 May 2008 18:41:22 +0100, Peter Fairbrother
that's a completely silly thread. why? Especially as you seem to be
cutting both halves of it?
it's bad enough getting things like 9x1, which is non-standard.
ah. not quite, I was about to suggest using 3/8" UNF or somesuch, but that
9.52mm not 9.25. What size is 1/8" BSP?
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
I thought about 3/8 UNF, but it's too big and 9mm is too small - also I
need a finer thread.
Allowing 6 threads (four plus two that don't engage) that will give a
part length of 3mm, which is okay - more is not, it would be too heavy
as well as too long.
It's for the injector of a rocket engine - the part with the outside
thread will be made of inconel X-750, and it would be awkward to cut the
outer thread on a lathe.
(also I'm not that good at cutting threads on the lathe - I get most
right, but mess some up, and there will be so much work already in the
piece and a die is more reliable)
The parts will be nickel-alloy diffusion-brazed after assembly, but I
want the extra security of a thread as it'll be working at 75 bar and
700 C on the inside face.
-- Peter Fairbrother
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