Thanks for the feedback everyone. Smoothstepper seems to do everything I need so is the top candidate at the moment.

Dubble - i take it you are the UC********* developer? You're the first mention i've found of the threading capability on the internet.

Yep, I'm one of the developers at CNCdrive Kft.
And the UC100 and UC300 can basicly do all what the SS can do, except it has not that high output stepping frequency, but especially the UC300 has some advanced functions compared to the SS,
like the analog inputs which you can use for example to feedrate override and spindle speed override with externally connected potentiometer, or just map that input into an internal variable and control other things using the variable value... it has analog outputs too. And there is a setup screen where you can attach any Mach3 internal functions to any inputs with simply selecting the function from a dropdown list.
And I was not talking about that the UC300-5LPT has 84 I/Os in total, can be useful for complex machines.
So, we have some advanced functions....

The UC devices could always (I mean from the very beginning) do threading with the single slot sensor, this is the same what MAch3 is capable of doing by itself.

And you know finding real info on the internet is mostly not easy or the informations can be missleading, because customers who are satisfied with a device mostly not writting anything on forums, because they are satisfied and using the device instead of writting on forums.

I am using UC100 and i really loved it:) The weired thing is i can't run the machine (Router 5ft x 5ft) at a speed higher than 200IPM in CV mode, if i go higher the rounding cornor in CV make the 3D carving pathetic:(. My router can rapid at 2100IPM using UC100 at 100KHz. ithout loosing step.

Acceleration is what leads to corner rounding, the faster the accel you have the less potential for rounding you have.
Hood

Khalid.

Mach3 is who precalculates the path and not the UC100, so the rounding of the corners are calculated by Mach3.
Also it is logical that it rounds the corners in CV mode, because the controller tries to keep the velocity constant which is not possible
in sharp corners as the machine axis need to be deccelerated and accelerated to go into and out of the corner.
The corners could be more sharp if you set the acceleraions of the machine axis higher.
(If your machine mechanics can tolerate that.)

If your machine could do infinate acceleration and decceleration then the corners would be sharp,
because then there would be no need to do any acceleration/decceleraion paths, so the time for these could be zero.

And you may set the CV stop angle to for example 89° then for corners on rectangle shapes will still be sharp
as Mach3 will cancel the CV mode on 90° angles.