I bought a used Lagun mill with an Allen Bradley 8400 control. I haven't actually gotten the thing yet but am wondering if the control is no good, will Mach work with the drives it might have? Will know more about it on Thursday. Thanks.

It is likely that the drives will just be analogue amps so to work with Mach you would need some form of converter/controller.
Hood

Got any info on the drives? There are a few step to analog converters out there (not sure of the current models) or, of the drives can be configured for step/direction operation. Don't care about the CNC control, just the drives.

Will pick the machine up in two days so I will let you know what they are.

Got any info on the drives? There are a few step to analog converters out there (not sure of the current models) or, of the drives can be configured for step/direction operation. Don't care about the CNC control, just the drives.

Not sure of the model of the drives but they are DC for what that's worth. About 1988 vintage.

Very unlikely that they can be set to Step/Dir at that vintage.
Hood

Biggest problem with 1988 vintage drive will be reliability. You might want to investigate some brushless drives as they will work when you need them. The older drives are getting to be a pain when it comes time to get tehm serviced and the cost of repair adds up real fast.

Machine works fine, screen display is colour but just old looking. It is a 4 axis machine so I have a spare drive if needed.

If the machine is working fine then why do you want to change to MACH? I would think that at this point you would be better off making some money with it and then use that to make the changes once you have some experience and more knowledge of what you want and need and what it costs to run and maintain the machine.

No, I didn't WANT to change it to Mach, but bought the machine with no real knowlege of it's condition, so was trying to get an idea of some kind of backup plan in case the thing was dead when I got it. Actually runs well, but I have no manuals with it and don't know how to set a work coordinate or make the control accept one, it keeps going back to it's machine zero as a coordinate zero. Anyone have any idea?