[zephyr9900]

I guess this is kind of a retroactive build thread, to describe what I've done so far.

For several years I had a Sherline CNC lathe, which was fairly stock. On the other hand, I spent eight years tweaking and modding and improving my Sherline mill, before I bought a Tormach PCNC1100 to replace it. The Sherline is a very capable lathe for its size, but I wanted a lathe that was more complimentary to my Tormach mill.

In specific, I wanted a lathe that would accept 5C collets. After some reading, I found that a Hardinge DV/DSM-59 was about the smallest lathe that took 5C collets. In November 2007, I bought a Feeler FSM-59 off Craigslist. This is a Taiwanese Hardinge DV-59 clone. No carriage at all, just a manual bang-bang crossslide (front and back toolposts, lever operated between two settable stops).

The lathe was filthy and 3-phase. I did get to run the spindle under power, and since I went equipped with a magnetic-base indicator, it seemed straight and solid. I had to rent a pickup truck to bring it home, which when I arrived at the rental place turned out to be a short-bed club cab...but the lathe just fit. It was a harrowing 55-mile trip home since the truck was so back-heavy!

When I got it home, I spent a couple of weeks of evenings cleaning the lathe of varnished coolant. The only thing I found to cut it was rubbing alcohol. I also dug and scrubbed a a couple of gallons of coolant sludge with about an inch of powdery swarf out of the sump.

[zephyr9900]

I live in a residential development, so there is no convenient 3-phase available. I borrowed a rotary phase converter for my initial playing with the lathe, but from the start I planned to use a VFD.

The Feeler, like the Hardinge original, has a 208V 3-phase, two-speed spindle motor that drives the spindle through a mechanical variable-speed transmission (that itself uses a 3-phase motor to adjust its ratio). The coolant motor is likewise 3-phase. The 110V control circuitry was fed from a stepdown transformer wired between two of the incoming phases.

After much online research into VFD's, I decided that the easiest course of action would be to simply use a VFD to synthesize 60Hz, 208V 3-phase from 220V 1-phase. The operation of the lathe would be unchanged as far as the controls were concerned.

I did read that the output of a VFD should never be switched, under pain of blowing output transistors etc. (akin to never unplugging a powered stepper motor, something I have unfortunately, though accidentally, experienced). The concession I made was to remove the handles from the forward/reverse and high/low spindle switches so I wouldn't accidentally actuate them.

Since I was bringing in 220V 1-phase, I could also bring in the neutral line and pull the 110V control voltage from one phase plus neutral. That eliminated the control transformer.

The three motors in the lathe add up to 2-5/24 HP (yup, that's what the nameplate says) so I bought a TECO FM50 3HP VFD, and a steel electrical cabinet to house it in, which I bolted to the right side of the lathe. I ran a piece of 3/4" steel conduit between the lathe's electrical cabinet and the new cabinet.

I wirenutted the new 4-conductor power cord into the input of the main contactor and tied the output of the contactor into the FM50's input terminals. I wired the VFD's output terminals back to the wiring bus to feed the three 3-phase motors. It worked, though it looked like a mad scientist's lashup...

[zephyr9900]

Here are the original and revised AC schematics of the lathe. Since the FM50 has built-in overload protection, I bypassed the overload contactors in the Feeler cabinet. Based on my research into ladder logic diagrams, I also "corrected" the schematic, with the contactor coils designated in circles and the corresponding contacts designated without circles. I also did some visual cleanup of the schematic (laboriously, with Picture Window Pro, since it was a GIF scan of the original paper drawing) for readability. I also drew a diagram of the control cabinet with all the contactors and other components labeled, to help myself in case of troubleshooting.

Since the speed-change and coolant pump motors are very small compared to the spindle motor, and can only operated while the spindle motor is running in this arrangement, they don't need separate VFD's. They just affect the output load of the FM50 a little.

But there is a self-imposed limitation of the way I did the VFD. I can't use it to vary the speed of the spindle motor without also varying the speed of the speed-change and coolant motors. If I wanted to replace the mechanical variable-speed transmission with VFD spindle speed control I would need to provide a separate VFD for the two little motors. Someday I do want to do this.

At this point I don't know enough about applying VFD's to non-inverter-rated motors to know how much I'd be able to vary the speed of the current spindle motor (I definitely want to keep the 3400 +/- top speed of the lathe--in fact I'd like to get a little more if possible) without damaging it. I've read that there can be cooling problems when running a motor at lower than rated speed, but I figure that wouldn't be a problem since I could just put a 110V or 220V boxer fan ducted to the end of the motor for forced-air ventilation.

[zephyr9900]

The stock control box had two normally-open momentary switches for adjusting the spindle speed, and a red-painted rod attached to the movable transmission yoke visible through a slot in the front panel to indicate the spindle speed.

I wanted to install a Tachulator digital tach, so to make room I replaced the individual switches with a two-way momentary switch (center off) from Automation Direct. Since I was now using the VFD to control spindle on-off I also wanted to control that from the control box. For that purpose I used a latching mushroom switch. Though functional, I'm not really happy with the overly-dramatic look (it's a spare E-stop switch I already had) so I'll be replacing it with an on-off latching switch that matches the speed-control switch.

The new front panel is a piece of pre-black-anodized aluminum which I engraved using a small v-bit. Not having a spring-loaded engraving holder, and having not leveled the workpiece quite enough, the depth (and thus boldness) of the lettering varies across the panel.

Since I have a one-pulse-per-spindle-revolution signal for the Tachulator (using a QRB1134 reflective sensor and a 180-degree white strip on the spindle handwheel), I'll be able to pull off a spindle index pulse to feed to Mach3 and eventually do CNC threading.

The final picture is the electrical cabinet after removing the stepdown transformer, cleaning up the wiring connections and adding the wallwart for the Tachulator.

[zephyr9900]

I had a couple of new-surplus THK KR20 actuators, with preloaded 1mm-pitch ballscrews and travels of 41.5mm and 91.5mm (1.63 and 3.60 inches). Prior to deciding to get crazy with the Feeler, I had doodled micro-lathe ideas using a Sherline headstock and the KR20's. The "bed" of the lathe was to be a piece of 6" square, .5"-wall aluminum tubing filled with concrete for damping. The single-minded use of this lathe was to be to turn finescale N (1:160) model railroad wheels from nickel-silver barstock, and the extreme accuracy and lack of backlash of the KR20's would be perfect for the application..

To keep the height of the X-Z mechanism down, I planned to attach the KR20's carriage-to-carriage with two steel plates, one attached to each carriage. One plate had threaded holes (spaced outboards of the carriage) and the mating plate had clearance holes. This would also give nice broad mounting surfaces on the "outer" faces of the assembly for mounting and for the gang toolplate.

The only thing that survived from this concept was the core of the X-Z assembly.

[zephyr9900]

After I bought the Feeler lathe and got the spindle up and running, I turned to the X-Z. I made a base to clamp onto the dovetail bed, that raised the KR20 assembly up to an appropriate height. Since the stock equipment (manual crossslide, tailstock turret) was designed to register on the front of the dovetail and clamp on the back, I followed suit. I made a toolplate out of .500" aluminum and toolposts (doweled in position) to raise a turning tool, a parting tool, and an arbor-mounted drill chuck to the spindle center height.

For aligning the Z-axis actuator, I used the Rollie's Dad's Method of alignment--I clamped my Best Test to the Z-axis interface plate, chucked (colleted?) a rod in the spindle, and adjusted the KR20's position until the indicator's swings were centered on equal numbers at both ends of the travel.

I then colleted the Best Test in the spindle, mounted the X-axis KR20, and adjusted its position (indicating on the frame itself) until there was no needle movement. I then mounted the toolplate and indicated its edge true.

This process brought up a major problem with this carriage-to-carriage mounting. The screws holding the X-axis interface plate to the Z-axis interface plate were head-down in a pretty inaccessible area. I had to grind the short arm of a hex key very short to even work with them. Likewise, the screws mounting the toolplate to the X-axis KR-20's base were upside down, though not as hard to get at.

The fundamental problem with this arrangement though was that, although there was no backlash at all, the narrow support between the two carriages allowed enough flexure to give significant chatter in cuts in even brass and nickel silver with the tool I would be using to turn the wheels. It is a Century Tool & Design CWPR-0630 plunge-turn insert with a width of .063" and a reach (depth of cut) of .250".

I never got around to boring and slitting the drill-chuck toolpost because this mechanism was a no-starter.

[Jason3]

Good stuff, very interesting. Nice photos too - I quite liked the one of the lathe almost completely behind the rear axle line on the pickup. I can imagine that was an interesting trip

Your electronics cabinet looks very like the one on my mill - If I'd thought of just using the VFD to supply 3 phase power like you did, I'd have saved myself a ton of work and one VFD! (I ended up using 2, one for the spindle, one for the coolant pump.)

Don't leave us hanging too long ...Really want to know what you did next...!

Best regards,

Jason

[zephyr9900]

I quite liked the one of the lathe almost completely behind the rear axle line on the pickup.

If I was halfway smart, I would have had the seller slide the lathe in heavy end first...but as the saying goes, hindsight is everything (and at that point I didn't know that the heavy end was the heavy end)... I was a little flustered though--that's the biggest used-stuff purchase I ever made outside a vehicle.

(I ended up using 2, one for the spindle, one for the coolant pump.)

Oh, just you wait, Jason. I'll probably be asking you about that before the tale is through. I'm already thinking about what it would take to dump the mechanical VSD and control the spindle speed entirely with a VFD. (acronym city--I'm sounding like the government...) My main questions will be--how much of a speed range can I reliably get from the existing non-inverter-rated 3-phase spindle motor and--can I use the FM50 to control the spindle, or should I get a nice vector-drive VFD for the spindle?

Randy

[Jason3]

If I was halfway smart, I would have had the seller slide the lathe in heavy end first...

Ya should've seen us bringing the turret mill home - we used a short wheelbase box body truck. I though it was gonna tip on it's side when we went out the driveway, then I'd swear the front wheels left the ground when we hit a big pothole when nearly home (150 Km trip). Bet it was the heaviest load the truck had ever seen, it handled like a boat.

To top it off, the rented forklift nearly tipped over getting it out - the wheels definitely left the ground that time...

It was worth it though

[zephyr9900]

In the midst of the mechanical development, I needed some workholding. I bought a set of Shars 5C collets, 1/16" to 1-1/8" by 1/32's because they claimed '.0006" TIR 1" from face' which was better than any other dealer of inexpensive Chinese collets claimed. So far, in the limited use to which I've put them so far, I'm happy.

A larger problem was mounting chucks. The FSM-59 has a "Hardinge" taper spindle nose, but it turns out not quite... A fellow traded me a used Hardinge 30AHC 3-jaw chuck, but it wouldn't lock on my spindle. I removed the alignment pin and found out why. On my feeler, the "Y"-shaped locking slot is a little farther up the spindle nose taper than on the Hardinge--about a half an alignment pin nose diameter.

I found an alignment pin drawing online and turned a 3/8-24 x 1" setscrew for the large pin diameter and shoulder. I screwed it tightly into the chuck and marked the side of the pin facing "up" the spindle. I then chucked the partially-completed pin in my Sherline lathe's 4-jaw chuck, offset it, and turned the pin nose tangent with that side of the pin's barrel. Fittingly, it was the last part I ever made with my Sherline lathe.

I've since bought a Hardinge 36AHC 4-jaw chuck that has the same "problem", but in this case I think I'll drill and tap a new alignment pin hole 180 degrees from the original one but offset in the correct direction. Until the 4-jaw is operational I don't currently have a way to do eccentric turning (barring shimming a pin in the 3-jaw, and I would be uneasy with that much shimmed offset).

I also fabricated a couple of collet-holding slides to replace the one trashed one that came on the lathe, using some nice full-extension ball bearing drawer slides, some aluminum channel and bar, and acrylic sheet.

[LeeWay]

Good read. Nice looking lathe too. It should produce fine results when you get it all hashed out.
I don't know if you will find many ready made axis that would really be suitable for a lathe.
Unlike on a mill, the table here is where all of the stresses translate to. I would think much more so than a table on a mill.
You might consider taking Jason't lead here and use some wide trucks and rails.
Looks like that is working pretty well for him.
Other than that, a double rail configuration would work well. It takes a little extra effort to align the rails, but once done, it becomes extremely rigid. Especially so if you use larger rails. I used THK HSR25's and HRW 27's. Just like the table on my mill.
I knew going in though that these would work great because I had used them on the mill.

The 25's may wind up being too tall for you, but the HRW 27's are shorter and wider and should provide a great base.
Even smaller than these would still work well I think.
Perhaps 20's. You can get Hiwin rails pretty affordably.

Anyway, here is a link to my lathe build if you haven't seen it.
http://www.cnczone.com/forums/showthread.php?t=59421
I'll stay tuned to see how you make out.

[BillTodd]

I'm following this thread with great interest. I really fancy building a bolt-on cnc carriage like that for my HLV-H (It'll be cheaper to build than a radius tool!).

Keep up the good work

[zephyr9900]

Lee and Bill, thanks for the comments. Thanks for the link to your build, Lee. I did see your video on Youtube a week or two ago while poking around for CNC lathe videos (the Pink Panther music stuck in my mind, as did the gang-tool plate). I will read through your build thread in more detail. That is a nice-looking (and performing!) lathe. I do want to make a larger X-Z for my lathe eventually, but that's getting ahead of the story:

I remembered seeing a CNC router that used a KR actuator as a leadscrew, and profile rails to actually support the gantry. I have some NOS Thompson AccuGlide Mini 10mm profile rails, each with two preloaded carriages, and their overall height (15mm) is close to the height of the KR20's (20mm).

I decided to put one rail with two carriages in parallel with each of the THK actuators. I just needed to machine a trench for the KR20's to bring the tops of all the carriages to the same height. I also wanted to have an all "top-down" assembly with no fasteners installed from underneath. After much fiddling with dimensions I arrived at a design where there weren't any overlapping fastener holes (just) and with a substantial intermediate plate for mounting the Z axis.

The Thompson rails, being so small, were easy to cut with an abrasive blade in my hacksaw.

I unfortunately didn't take any photos of the new mechanism during assembly, so I'm attaching some progressive CAD screenshots instead.

I did the alignment essentially the same as the first mechanism. I aligned the KR20's to the axes, then aligned the Thompson rails to their corresponding actuator. Since the rails are bolted down with tiny 2.5mm screws, after alignment was done I ran a bead of epoxy down each side to help "pot" them in place. I don't know if that made a difference or not...

The new mechanism is very stout. There is a Thompson carriage under the front and back toolposts, so the load path while cutting is very direct. There is no chatter at all and I'm really happy with the mechanism. All the structural parts are aluminum, since I have a lot of it, but I'm considering this a prototype and will sooner or later redo it in steel or cast iron. Or not maybe... The current toolposts are doweled in place, but if I go to a ferrous toolplate I'll put T-slots in it.

Things still to do are add home/limit switches, do some cable strain reliefing and management, and chip protection. So far I've just been using cardboard shields and plastic bags to drape over the mechanism to keep chips out of the works. Bellows would take up a lot of the travel, of which I don't have any excess so I'm not quite sure what to do.

I'm driving the mechanism with a Xylotex board, a duplicate of the drivers I built for my Sherline mill and lathe. I rearranged the new electronics cabinet and just bolted the Xylotex box in whole, minus the cover.

[zephyr9900]

I uploaded a first video of the Feeler in action to Youtube[ame="http://www.youtube.com/watch?v=X4xK6ATL5uc"]feeler1[/ame]
subject to the 30-second video limitation of my digital camera I need to learn how to transfer video from my digital camcorder to the PC so I can put up a better video...

[Jason3]

Very nice - it seems to be cutting really well! how big is that part - it looks about 3/8"? Is that the nickel-silver bar stock you mentioned earlier - can I ask why you use it, and what characteristics it has - machinability, etc? (Just curious...) I did a quick search, but nothing much came up except knife parts!

I also like the look of that insert tool - I need to find something like that for my machine. Ideally something that will turn and part in one tool. I've been looking at the Century Tool website, but it's a little light on information.

Looking forward to seeing what you come up with for way covers

Did that movie just change?? Or is it just me...

Best regards,

Jason

[zephyr9900]

Thank you, Jason.

Nickel silver is basically brass with some nickel added (the barstock I have has 12% nickel) for corrosion resistance (the oxide is still shiny and electrically conductive). I'm using it for prototype model railroad wheels so I can machine and use them as is, without having to have them nickel plated as I would with brass. NS is also popular with custom fishing rod makers for the hardware for pretty much the same reason. I think the specific alloy I have is 792, that also has a percent or so of lead to make it freer-machining. It is still tougher than brass though and has a machinability of 60% of 360 brass.

The barstock in the video is .50" diameter. I'm attaching a photo of the finished part, after I machine the details with my Tormach mill. The diameter over the flange is .430"

Century Tool's website is frustrating. There is a little bit of information on each page, but no "system" summary of info. I'm using a SWAR-10 stick holder (.312" square) with the insert. I cut off the rear of the holder because it was long and unwieldy (they're made for screw machines) and used it for years on my Sherline lathe. At the time I first bought inserts, Century gave a free holder with your first order. I was an idiot and didn't think to ask for a double-ended holder--I could have cut it in half and had two usable toolholders!

You mean a waycover even better than the old plastic bag? If I think up anything clever I'll let you know. I've been kinda hoping you came up with something clever first...

Wow, you must have jumped right on the post. I didn't like the way the first video turned out on Youtube and it was only up for 10 or 15 minutes. So yes, this is a replacement video. Shows more of the cycle (I did a little reworking in the meantime) and is a little closer and maybe a little better focused.

Randy

[pete from TN]

Beautiful lathe and I cannot beleive that part is only .5" dia. What endmill did you use to do that machining on the tormach? Agian nice work....peace

[zephyr9900]

Thanks, Pete! I faced the hub and counterweight and machined their profiles with a .063" endmill, machined the spokes with a .020" endmill, and "chamfered" the spokes with a .020" ball-end (the .020's in the Proxxon high-speed spindle). I used Sheetcam to generate the gcode for the flatmills but hand-drew the toolpaths for the ball-end.

Randy

[Jason3]

Ah, thank you - good explanation. Nickel silver sounds a nice material, and that's a neat little wheel! Can we see the fixture you use to hold that on your Tormach? I sometimes reckon the hardest thing about this game is holding the part...

What is the max. diameter you can part off with the SWAR-10 stick holder? I've been talking to my usual supplier, he has some ideas but that still looks like the best bet. I'm guessing the inserts are pricy...

My clever idea for way covers was to plan for them first, next time It looks like you would have room for bellows on the Z, how about a rigid cover for the cross slide? It could just run right over the top of the stepper, and fold the sides down to cover the front and back rails and KR actuator... I'll be doing a rigid cover for my cross slide, and bellows for the Z, I think.

Best regards,

Jason.

[pete from TN]

Or is that a proxxon spindle mounted on the tormach? Either way nice looking part. What was the run time on that thing.... Man I wish I could get my hands on one of these beautiful toolroom lathes like the feeler or hardinge to cnc.. SWEET!!!