"Matty F" wrote in message
...
On May 14, 12:12 pm, Gib Bogle wrote:
Matty F wrote:
Does anyone know if dies are available to cut the thread on wood
screws, i.e. a tapered thread?

Have you considered lost-wax casting? There might be local foundry that
can do
that. You'd still need to machine the head.

I'm sure I can make a device to hold screw blank while I'm grinding
it.
It will be quicker to grind it than to drive to a foundry and pick it
up, and they would charge $100 for their time.

Why not buy a modern screw, cut the head off, weld a bit of metal on, file
it to that old fashioned shape you want?

John Rumm wrote:
On 13/05/2010 01:51, Matty F wrote:

They are produced commercially by squishing (tech term there) between
2 halves of a tool.

I want to match screws made the old fashioned way, like 100 years ago.
I think I will make an adjustable die and see how it works on brass.
My uncle made dies out of old files while he was a POW in WW2. I have
better facilities than he had!

I forget the correct terminology for it, but there is a screw cutting
technique that basically uses a comb ended tool to cut several turns of
thread in parallel on the lathe. Starting off being the hard bit - since
it needs to "travel" along the work at the correct rate for the pitch.
However once there is the rudiments of a thread there is can follow it,
and deepen it on each pass.

I know the tool as a thread chaser, it was used after cutting the basic
threads onto engineering bolts.
By using a rest and holding it against the left hand side of the thread,
it cut the bottom and top curves to perfection. I've never seen this
sort of tool cut threads from blank bar though.

Dave

On Fri, 14 May 2010 22:02:35 -0700, Matty F wrote:
Where is it? Looks like MOTAT.

How observant of you

Is the mercury arc rectum-frier for the tram system still running there?
It was the only 'live' one of any significant size I'd ever seen, and
completely captivating to watch, but that was getting on for a decade ago
now.

cheers

Jules

On May 18, 5:14 am, Jules Richardson
wrote:
On Fri, 14 May 2010 22:02:35 -0700, Matty F wrote:
Where is it? Looks like MOTAT.

How observant of you

Is the mercury arc rectum-frier for the tram system still running there?
It was the only 'live' one of any significant size I'd ever seen, and
completely captivating to watch, but that was getting on for a decade ago
now.

Yes it's still working fine. They are very reliable. There are four of
them running and one is visible.
http://i46.tinypic.com/120qi6o.jpg