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Of course my favorite Edison recorder is my Edison Pro studio recorder, It is sensitive, will record at any temperature and record deep grooves. You can change the diaphragm and stylus in just a few minutes. Of course even suggesting it, is kind of silly, it is not something that common, by any means, and is tricky to use, and you have to build a special carriage for it. This unit also with a change of the stylus, it can record four minute, or even Diamond Disc masters. There is still lots to learn, even though I have gotten excellent recordings from it, I know it can still do better work. The little odd knob on the front is the advance ball, something that even Westrex lathe heads had even in the 60s.

Will definitely be printing this thread out to keep!!

Scott

What's the difference in the 2 minute cutter and the 4? Do you have pictures.

To help answer your question about the difference
between the 2M and 4M cutters, it's very helpful
to draw yourself a little scale drawing of the
groove profile of the two formats, with dimensions.

Once you have the drawing and the numbers in front
of you to look at and to think about, then the
shapes of the cutters will be more evident.

Basically with the 2M format the grooves are spaced
on .010 inch centers. The grooves are of a semi-circular
profile since they are incised by a cylindrically shaped
cutter that has a hollow end. As such, the groove depth
and the groove width both vary at the same time as the
cutter moves up and down.

The diameter of the 2M cutter is .040 to .041 inch.
It can be seen right away that cutting a semicircular
profile groove with a .04 diameter sapphire cutter
which only moves along .01 inch per 360 degree turn
of the cylinder record, presents a potential problem
if the cutter goes too deep into the record.

This is exactly where the little scale drawing comes
in because you can lay out the center-to-center
groove spacing at say 100 times size. That will
yield two vertical lines an inch apart.

From there we now can take something circular and 4
inches in diameter and call that the cutter at 100 times
size. A plastic coffee can lid or a small lid of
any kind or anything 4 inches in diameter. Make a paper
or a cardboard cutout if you have to.

Now place it centered on one of the lines and
lightly trace where the bottom of the curve digs into
the record. Mark the bottom. Then move it over to
the other groove center line and trace another cut
at the same depth. Then look to see if there is
any "land" at all remaining between the two cuts.

If there is a flat uncut place there, then that
represents grooves which have no echo.

If there is no land between the semicircular cuts
and you see that one curve touches the other curve
that would be an "echo-around" situation.

You can now take it one step farther and lay out
two cuts which have some minimum land between them.

Then take your accurate ruler and measure the depth
of the cut which yields some minimum land. You will
find that this dimension on a 100x scale drawing
measures about .2 inches.

.2 divided by 100 comes out to .002 inches, which is
indeed about the average groove depth of an Edison
2M record.

This is about the extent of my own personal hands-on research and experience. I have not ever yet so far
done anything with the 4M format. Never even seen
a 4M cutter.

However, one can conclude that since the center to
center distance of 4M grooves is exactly half that of
the 2M grooves (namely .005 inch instead of .010 inch),
that everything will be roughly half of that found
on the 2M format.

I have heard a few times that certain 4M cutters
resemble a doorknob which has a wedge cut out of it.
Turning this doorknob so that the wedge will make the
cut then introduces a situation where it can be
allowed to cut a bit deeper without widening out the
groove so much as a circular profile cutter will.

Again, that can all be laid out at a large scale
such as 200x and play around with various cutout
shapes, then scale the depth of the cut to see how
deep it can go before using up all the land between
grooves.

I've done this whole drill with the 2M format several
times to see it clearly. For me it gets a bit foggy
though when it comes to the 4M stuff though, because
that is all still numbers and lines and paper to me
because I never yet have experimented with the actual
physical hardware.

I do have the definite hunch though, that trying to
use the 4M format to record and then play that original
master is not a very workable idea because the tiny
grooves are just too delicate and dainty to provide
many plays.

That is why 4M format works so well for moulded
records, because the master is never called upon
to be used for direct playback.

I hope this helps some to visualize the difference
between 2M and 4M cutters.

Chuck