Problem- DB9 Data switch for steppers?

[Fastest1]

I have a Cnc Sherline lathe and mill. Both use the same controller (a hobby cnc pro , I built). I got tired of changing cables back and forth and decided a data A/B switch (1 for each axis)would allow me to simply flip a switch after depowering of course and then be able to use the other machine. It seemed to work when I initially connected it all up. However then all of a sudden the steppers on both machines were locked up. I did have to make some adapters from DB9 over to a mil spec amphenol plug but that shouldnt cause any problems. I do believe because I have the sheilding connected to the DB9's on both ends it is causing some grounding interference of some form. Opinions? I do run an A/B switch for 2 different DB25 cables going to 2 different machines and this causes no problems. I dont see why this wouldnt work. I am thinking of clipping the shields at the db9 of the machines. To eliminate the ground loop or whatever it is called. Anyone seen this done? I never use both machines at the same time anyway but I do use them back to back plenty.

[bharbour]

I don't think it too likely that it is a ground loop issue. I would say pop open the box on the AB switches and look at the switches. Most of those switches I have looked inside don't look like they would carry an amp without problems. I suspect you will find heat damage to the switches or wiring.

BobH

[Fastest1]

I wondered about their durability. Of course all of my steppers are less than 3a. Not that it means the switch was strong enough for that. I swear they worked right at first but then I could not get it to do anything. Well except lock both steppers and some undesirable behavior. I will have to test the wiring. Thanks I might have to test it out again. Thanks