I'm in the throws of converting my SX3 to CNC via the Syil kit. I did not purchase the Syil spindle controller and I think I'm going to do my own thing.

My question, has anyone has done "semi-rigid tapping" with Mach3 on their SX3 machine?

With the "new" Sieg electronics it is possible get a tachometer input to Mach3. Simply connect any hall effect sensor to the Syil breakout board. This is possible because the ground potential is the same. Do NOT try this with the "old" Sieg electronics or smoke and sparks will result! Also if you try to do this connection, make sure your machine has no voltage between the two grounds. I have tested this, and I get a working RPM tach from Mach3 with a pulley ratio of 8.

Now, my understanding of Mach3 is that it controls the feed rate based on spindle speed with G95 gcode. This means that possibly even with the Syil spindle controller board semi-rigid tapping is possible. I don't have that board so I can't try it. I'm not sure if the control of velocity is good enough either, but it is something to try for the adventuresome.

I should get my spindle control setup soon and I'll post an update on my progress with that, and the semi-rigid tapping.