Hardinge HC Lathe - CNC Conversion

Im a bit late to this thread but youve done something I am just considering.
Any chance you could answer more questions at length?
Was this a Hardinge "2nd operation" Lathe to start?
Is there an optical encoder or resolver on the spindle for position control?
You mention vfd in an earlier post but I dont see how you can thread repeatable without syncronizing the spindle and feed. no doubt youve done that.
Amazing work and workmanship.
Hope to hear back. Matt

Hi Matt

This started off as a Hardinge 'HC' lathe - a weird little production lathe fitted with an eight position tool turret, and no tailstock.

Typically, CNC conversions of these sort of lathes have used the tried and trusted solution whereby a separate toothed drive off the back of the spindle drives the encoder behind the head stock, (a bit like the Accuslide and Omniturn CNC conversions).

I've went down a different path, using the encoder fitted to the rear of the new spindle motor, and driving the spindle with a toothed timing belt at a 1:1 ratio. The encoder on the motor sort of keeps track of the spindle position, allowing synchronisation during threading operations. This is a less than ideal solution, as while the timing belt will prevent large errors, load on the spindle could possibly stretch the load side of the belt and introduce slight errors, and minor variations along the length of the spindle drive belt would cause a periodic error.

Anyway, I've had no problems with this setup using single-point threading, but I wouldn't want to try rigid tapping with it. I certainly wouldn't recommend this as a solution for anyone else! The only reason I did it this was that being a lazy sod at the best of times, when I got the new spindle motor and found it already had an encoder fitted, I believed that it would save me mucking around with a separate encoder, drive, and bracket on the headstock.

Cheers, Steve

Most Impressive well done.
cheers john

mgallelli wrote: You mention vfd in an earlier post but I dont see how you can thread repeatable without syncronizing the spindle and feed.

LinuxCNC just needs to measure the spindle position to know where to place the Z axis for threading.

See this video to see that the spindle does not even need to be powered and in gear for this to work: (He is turning the chuck by hand during a threading operation, then adjusting the workpiece position to pick up a pre-existing thread, then he engages the clutch to finish the operation)

Hello:

I too, am a bit late to this thread. Excellent work, a very clean upgrade.

I've had basically the same lathe with an Omniturn attachment for about 15 years. The Hardinge drive belts on the variable pulley system finally gave out and I just tore it apart to convert to direct drive. I had also decided on the GT3 belt system and have been searching the net for pictures or info on other conversions so I don't have to reinvent the wheel. Unfortunately, all I can find is people saying they've done the conversion and are really happy with the performance improvement, but give no part numbers, supplier names, or even descriptive pictures of the completed work.

Any chance you might help a fellow do it yourselfer out? Perhaps give me a few details such as pulley diameters(part #'s), the supplier if you were happy with them, belt width and maybe pitch choice. Also, any issues you might have run into, and maybe how you mounted the new pulley to the (I assume) modified factory spindle pulley.

I already have a good idea what to do, but it would be nice to hear from someone who has successfully accomplished the task.

I swapped the controller for this lathe onto my other Omniturn which had a bad control so I could keep producing parts, but I want to get the spindle back together in preparation for converting it to Linuxcnc.

Thanks ahead of time,

Karl
AKA Gearheaded

gearheaded,

I assume your question went out to the OP, but I figure I would chime in as may have some useful info for you.
I used Eagle PD on my AHC retro. It's the herringbone style timing belt. I would assume the GT3 type will require similar adaptation.
I post machined the hardinge headstock pulley and mating herringbone pulley as I could not find a matching system that would fit inside the head. It's direct drive 5hp motor and 1:1 ratio. The motor pulley was an off the shelf item with taper lock hub. The only negative I found is that I get some vibrations at higher rpm possibly from the long belt. Maybe less of an issue with the GT belt. Not sure. The herringbone has tendency to rise up on the pulley on the trailing side before it drops into the grooves and I found that it has a quieter direction of rotation if the chevrons lead in the direction of your main rotation. I of course got that wrong on my build.
I can dig up photos if that helps...