RE: [CAD_CAM_EDM_DRO] CNC lathe retrofit and phase converter

Ian and Bill -

Thanks for the responses on filemaking. I was able to form the
teeth as you described, and I hardened them, but without the
tempering. They seem to dig well into the mating part. These
teeth won't be seeing typical file service, but are actually for a
disposable product that may do fine without the toughness of a
tempered core. The size is also on the minitiature side of
things - three teeth fit in an area .08" x .06". My eyes are
starting to cross!

Thanks again for the advise, and thanks to all for tolerating the
off-topic question,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Ian Wright [mailto:Ian@...]
Sent: Wednesday, January 09, 2002 5:13 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] CNC lathe retrofit and phase
converter

Hi,

I'll just add a little to this thread. The only way to cut sharp
file teeth
is with a chisel as Bill says and this is still done but by
automatic
machines which usually use carbide chisels and hammers which are
sprung
towards the work but repeatedly pulled away and released by snail
cams. It
is essential that the work has a film of oil on its surface and
some studies
have suggested that it is this oil which actually raises the tooth
by
hydraulic forming. If you want to do it by hand it is perfectly
possible and
I have made many files this way using antique tools (it was a
common trade
in this area and so I learned from some of the last hand cutters
still
working). The technique is to hold the blank firmly down - this
can be by
clamping it in a vise but was originally by holding it down onto a
lead
block fixed onto a stone 'anvil' using a leather strap which was
fixed to
the stone at one end and had a 'stirrup' into which you put your
foot at the
other end. The chisel is just a piece of tool steel wider than the
workpiece
and was usually triangular in shape with one edge sharpened from
both sides
to about a 30 degree included angle. This chisel is placed on the
work at an
angle across it and at what will become the front end of the file
and is
angled away from the worker at about 45 degrees. It is given one
hard blow
with a hammer (the originals had their heads angled towards the
worker so it
was easier to hit the chisel cleanly) and the chisel is then
withdrawn from
the cut so made and placed back on the work closer to the worker.
It is now
slid along the work until it rests against the back of the first
tooth and
is struck again. This is repeated until the whole length of the
file is cut.
It is usual for a second set of teeth to be cut on the 'opposite'
angle (a
double-cut file) in exactly the same way. If anyone is really
interested I
can post some pictures of the original tools I have on my website
although
it may take a day or two to get it organised.
For small files like 'needle' files there is also a technique
called
'etching' which has nothing at all to do with acids and resists.
In this
method a triangular bar of tool steel is file cut on the corners
with a
special type of teeth. In use, the corner of the bar is rubbed
across the
workpiece so that these teeth effectively cut grooves which become
the
teeth. Files made this way are not as sharp as chisel cut ones but
are far
more controllable on small work. The needle files made by Stubbs,
Vallorbe,
Spear and Jackson etc. using this technique are far superior to
the modern
chisel-cut needle files from India and China.
Whenever you buy a new file it is a good idea to stone the safe
edge smooth
before you use it as the ragged ends of the cut teeth can
otherwise tear
your good work to pieces.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: "Smoke" <smoke@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: 09 January 2002 15:46
Subject: Re: [CAD_CAM_EDM_DRO] CNC lathe retrofit and phase
converter


> I'm really surprised to see this info here! It was told to us
by the
> instructor (now retired) at the college. We had to make a lot
of tools
but
> fortunately making a file wasn't one of them!
>
> Smoke
>
> > >Question #3: (OT)
> > >How are file teeth formed?
> >
> > With a hot chisel and a hammer, allways remembering to chill
the chisel
> > frequently by dunking it in a bucket of water, so it won't
lose it's
> hardness.
> > When you have enough teeth, let the file blank cool. Press
refractory