Re: Milling Glass

Hello,

Walk into a vinyl sign shop and ask them where they purchase their
cutters...

There are two types used: tangential and drag-knife. The tangential
is mounted with the ability to turn (C axis) into the direction of
the cut. The drag-knife type is probably what you will want. This
cutter is shaped like a TINY #11 ex-acto blade (if it were made from
rod stock) The top is ground to a point, and rests in a holder. There
is a magnet in the top of the holder, and a ball bearing (single
ball). The holder is often aluminum, and some are available shaped
like a plotter pen, for obvious reasons :-) Techno-Isel sells one,
but their price (as usual) is ridiculous,IMO.

The cutters are relatively cheap (say 15 bucks), but the holders can
be pricey; and not much of a lathe project for anyone with some
experience.

The Drag knife style works fine until you start making small
designs/letters. Then, the offset from center of the blade point
(that's why it is called "drag" knife) starts to be more than the
move length and the cut path is distorted. Tangential cutters solve
this problem, but require a dedicated axis and software which has an
integrated C axis for tangential cutting. Dancad/CAM is one freeware
example which does have this capability.

Hope this helps.

Ballendo

P.S. You will want to have a "floating" head for this. While we're
here, I'll let you in on a secret. You can do some of this cutting on
any cnc machine WITH an ex-acto blade and round handle holder! Simply
drill a vertical hole through a block of plastic, wood or metal,
sized so the trailing edge of the blade can "turn" the knife. Often,
you will need to tape a coupla washers (for added weight) to the
knife holder(handle).

A longer term setup might use a bronze bushing through an alum block
mounted in Z. With a setscrew collar on the blade handle for weight
and "lift"-ability...

You can try other ex-acto blade shapes. There IS one which is better
than the #11 (which works), but I don't know its' number. Remember
the words above about distortion of cutpath based on feature size
versus blade "trailing" dimension. Have fun!
__________
________/ /
_____/ Ascii art of the "better" ex-acto blade shape.
/
__________/

Hey, I just realised that you could grind away at the point of the
#11 until the "trail" dim was whatever you wanted!!! The distance is
measured from the CENTER of the MOUNTED blade/ holder.
/| _
/ | / | Modified #11. Flat across top
/ | #11 type blade / | would slope down toward right.
/ | / | (Ascii art limits exact-ness)
| | | | pun intended :-)
| |
| |

> Where can one purchase vinyl cutter suitable for
> fixing to a mill/router?
>
> Peter