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I like the idea of reusing the resolvers simply for the ease of it. I was a little worried about the compatibility, so I did a little surfing the interwebs as well as disassemble a resolver. Found out that the tach is a servo tek dc generator producing 20.8v/ 1000 rpm. The axis resolvers are Harowe servo corp part number 11BRCT-300-F95A/5-01, and the spindle resolver is 11BRW-300-F58A. I circled them in the photo below.

The resolver is kinda a strange duck, Hardinge mechanically geared the tach and resolver up 5:1 vs the ball screw. I think this was done to increase the accuracy of the machine. because of this I am not sure about how emc or the 7i49 will handle the resolver imput. I assume that emc will be able to scale the 7i49 output to correct for this? Also its not clear if the 7i49 can output 12v to power the harowe resolvers or not? I guess they could run on a lower voltage however I think I would loose some fidelity. I think I may call mesa tomorrow to discuss. If the 7i49 will work, then I think thats the route to go.

JR1050 I would apreciate a copy of the Hi acks schematics, would help me alot since I will be maintaing them. As for the spindle motor, it is a very large dc motor, which got me thinking, I wonder if it could be rigged up as a true C axis using emc?

The Allen bradley 7300 series controlls are huge, I had 3 shipped with the machine, they weigh around 300 pounds each and are 3ft x 3ft. I tried all 3 on the machine, none worked, however I did get a free fire works show when the tantalum caps explded on one . They are on Ebay now. I didint have room for the machine either, I had to sell my Ahc to make room. I bid on it casually, didint think I would win, .

I scrapped the Hiacks in favor of AMC 25a20's for two reasons,the hiacks were huge and I didnt have the room and they used tachs which required eithier reusing the resolvers or buying super expensive encoders.I have Hiack amps on my B&S mill and if memory serves me,you will have to jump the contactor and pull the inhibit pin low,I cant remember which pin it is, H or J ?Then you can put a battery on the inputs on the amps,I use a size aa...

I have another hnc and like the idea of using the resolvers,but then i need a resolver and encoder board(u need an encoder on the spindle).I can scan the Hi ack book.send me your email and Ill try to get it done in the next couple days.Yes,you could use the spindle as a c axis.The pitch on the screws is .200,not 5mm...I surfed all day,Im beat....

On the attached schematic, I jumped pin E to pin B to disable feed hold. next you just need to apply a voltage to pin H, with ground at pin G, to move the other direction reverse the polarity. I used a AA battery with some wire taped to the ends. You might want to remove the drive belts from at least the x axis for safety reasons. By doing this you are effectivley forcing the motor on. The slides will not respond to the limit swithces so you can crash the axis into its end of travel if not carefull.

use the 7i49 resolver / analog addon servo card it will work fine , and some io addon cards for example the 7i42TA , as theres a lot of inputs and relays to operate.
yes the spindle is nothing more than an overgrown servo motor , so can be used as a c axis , the spindle also has a resolver for screwcutting etc
all the amps use standard 10v analog dc inputs , so the conversion is mostly straightforward .
scaling is done from within linuxcnc and configured in the hal files

their are a few hardinge conversions done by Linuxcnc members , so your not alone

Alloy Craft wrote:It was possibly done to increase the output of the tacho for improved feedback at the low rpms typical of lathe feed rates.
LinuxCNC doesn't care, it will just need to be factored in the resolver-revs-per-inch scaling.
You can either keep the tachs and drives, swap to other velocity drives and keep the tachs, or swap to torque-mode drives and ignore the tachs.
I would probably start by seeing what works