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Thread: HF 8X12 CNC Conversion starting...Need Help

  1. #1
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    HF 8X12 CNC Conversion starting...Need Help

    Having more or less completed my Promica X3 build some time ago, I decided it was time to tackle the conversion of my Harbour Freight 8X12 lathe. So...I started researching. There is not much info out there for this particular conversion and definitely, no kits ala Promica. So I'm gonna tackle this the hard way and use what knowledge I gained with my X3 build along with whatever info I can glean from this site and the internet and start my lathe conversion.

    A little while ago I was turning something on the lathe when suddenly this horrendously load pop (kinda like a gigantic party popper) accompanied by flying tar, paper,smoke and who knows what else. Seems that one of the capacitors had blown up. Since the lathe would still start and run, I figured it was the run capacitor. Replaced that and everything was normal again.

    However, this sparked my desire to convert to VFD. Sourced a 1 Hp Weg inverter motor from ebay and ordered a Teco JNev 1 Hp VFD. Milled out a motor mount plate and added a 2" pulley to the motor. Then, I built a new enclosure to house all the controls. Still awaiting delivery on my Tachulator which will reside in the faceplate covering the spindle box. Anyhow, I am very happy with this VFD conversion. I am able to run from 0-1200 RPM off the 2" pulley. I also have larger pulleys if I desire to increase the upper end. So happens that with this pulley, the Hz almost directly corresponds to the RPM. At 5 Hz, the chuck is rotating at 5 rpm, 60 rpm at 60 Hz, and so on. And the torque from this setup is unreal. I can't even think about slowing the chuck down even at 5 rpm. This thing would rip my hands right off my arms!!! This acts totally different from the setup on my mill which uses a non-inverter motor and does not have the sensorless Vector .(Teco FM50) I can definitely slow down the mill spindle with moderate pressure at very low RPMs.

    Anyhow, Also added a 6" Bison 4 jaw and 3 jaw chucks. ( More ebay finds) Have not yet turned a backplate for the 3 jaw, but the 4 jaw is done and exhibits only .0001" runout! Added a Phase II AXA QCTP and a chip shield.

    Okay, so here are some of my ideas for the CNC Conversion. The Z axis seems rather straightforward. I would like to use a pulley drive system so that I can hide the stepper motor in the left base area and everything is hidden by the stock gearhousing cover. I intend to use the computer and electronics that I built for the X3 mill. I will simply unplug the connections from the milll and reinsert into the lathe. If this becomes too much of a pita, then I would eventually build dedicated electronics for the lathe. However this costs $$$$, so I'd rather try it the first way for now.

    The major problem that I see in these lathe conversions is the lack of space in the X axis to mount ballnuts. I have seen several workarounds including but not limited to:
    1) Forget the X axis ballscrew and just use the existing ACME
    2) Mount the ballscrew behind the compound slide
    3) Mount the ballcrew on the front or rear sides of the compound slide
    4) Get a small ballscrew and make it fit

    Of these options, I tend to like option #4. There would not be exposed ballscrew for swarf to get in, nor would there be a ballscrew (ie. dagger) sticking out the back of the lathe. I have done some measurements and think that an 8 mm or a 3/8" ballscrew with its teeny little ballnut could fit.
    My idea would be to have the ballnut screw into a small elongated carrier that is bolted to the underside of the compound slide. My only problem with this approach is I would be required to thread the carrier .664-32 UNS. I have been unable to find a tap in that size thread and (he-he) I don't know how to thread on a lathe (yet). Also , I don't know if a 3/8" ballscrew is hefty enough to function properly in the X axis. I have also considered milling out the portion of the saddle where the ballscrew would run through. By widening and deepening the slot, I might be able to create enough room for a slightly larger ballscrew and nut. My only concern is how much can be removed before the saddle loses some rigidity. Anyone out there try this yet? Here is the point where I hope people will chime in and give me their two cents worth. I'm itching to start, I just need some answers or opinions. Thanks!!

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    Anyone know a source for small (say 6 mm id) AC bearings. Was set to go the 8mm ballscrew route, but sourcing parts and also having to deal with machining the ballscrew won't be the easiest. May have to go the ballscrew sticking out the back way. I can use a larger screw and mount the bearing on the back of the cross slide.

    Also considering getting rid of the compound as it won't be needed after the conversion. If I replace the compound with a riser block, I might even be able to extend it and hang the ballnut off it. But that would mean having the ballscrew sticking out the front side of the lathe. More things to ponder



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    I get my small components from Precision Mechanical Components Timing Belts Pulleys Spur Gears Couplings Bearings Sprockets Retaining Rings Brakes Helical Gears Clutches Universal Joints
    They have a good online catalog to order from, and have good prices and service.

    BTW: I didn't type in that link like that. I only typed sdp-si dot com. It went nuts when it posted!

    Beer is always good. If you can't figure it out on beer, it's not worthwhile. - knudsen


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    Isn't there some kind of law that says that the toolbox that the lathe sets on must not cost more than the lathe itself :-)

    Donald


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    Quote Originally Posted by dneisler View Post
    Isn't there some kind of law that says that the toolbox that the lathe sets on must not cost more than the lathe itself :-)
    LOL!! If that were my lathe, it would be sitting on a "Stack-On" cabinet from Mega-Lo Mart!

    Beer is always good. If you can't figure it out on beer, it's not worthwhile. - knudsen


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    Thanks Blades,
    SDP-Si is definitely a great place. Sourced the timing pulleys and belts for my mill spindle conversion there. Cannot find any angular contact bearing on their site though. May just have to go with a ballnut mounted on the back of the cross slide, it will definitely make the conversion simpler.

    As far as the toolbox goes, my wife always says that tools are a lifetime investment so you might as well spend a little extra to get something that lasts!



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    bearings

    Nice job so far...looks great...i get all my bearings (mostly) from VXB.

    im still looking at cnc'ing my 8x12 i know what im gonna do, just getting ready to start another job, life's a bit weird now lol...

    Bodysnatcher



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    Thanks bodysnatcher!

    I have been following your thread and I am amazed at what a real machinist can accomplish. I myself had zero metalworking experience until I happened upon this site a little over a year ago. Everything that I know has been gleaned from this site.

    Anyhow, I am in the process of ordering up ballscrews for the build. Hope that they will arrive in time so I can start working on this project over the holidays. Was able to pick up a couple more things on ebay for the lathe including a telescopic ball screw cover and an Albrecht chuck.

    I will post pictures as more progress is made



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    Tachulator installation

    I returned home from a short vacation to find my tachulator board on the porch. So I quickly designed the faceplate mounting and took it to the mill to make the plate. Here is the milled faceplate ready to install and a test fit.

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    Wow, that wasn't too bad. Also made a spindle counting strip with aluminum tape and flat black paint. Figured I would make the maximum number of divisions on the strip for best accuracy. Didn't occur to me that only the dark areas count.. not the unpainted areas in between. Instead of 16 divisions, I ended up with 8. Oh well, wasn't too hard to make except when the spray painted tape blew into the pool Eventually I'll make another one with ... yes... 16 dark lines. I am so stupid.

    But that is where the brain farts just got started. In my haste to get the Tachulator mounted, I forgot two things. One, incorporate the hole in the original faceplate into the design, and two... ALWAYS CHECK THE WIRE ROUTING BEFORE YOU DESIGN AND FABRICATE SOMETHING. If anyone out there ever decides to do a similar install, MAKE SURE YOU CHECK CLEARANCE FOR THE POWER JACK.

    Problem #1 was taken care off by slighty expanding the faceplate hole that accomodates the digital display after I realized that the original hole was still visible. Problem #2 was a bit more difficult. I ended up dealing with that by unsoldering the power jack outlet from the board, rotating it about 45 degrees and resoldering into new holes. Unfortunately, somewhere along the line I managed to screw up one of the circuit board traces. Luckily my handy Fluke helped me to find the problem area and I soldered a jumper wire across the broken trace. Gee...Do you think the Tachulator people will still honor the warranty?
    (P.S. I've never tried to do anything like that before, but I figured it was a learning experience and there's no way I was gonna remill the faceplate)
    Anyhow the Tachulator works. Here is the rotated power jack and the 16 ... oops I mean 8 division tape in place.

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    Next, I set about wiring the Tachulator up. Plugged a 9V adaptor into the outlet I had previously incorporated into the enclosure, and snaked wires into the spindle hosing. Made a simple L bracket attachment to hold the infrared sensor and quickly turned a knob on the lathe. Once I set the dip switches properly (How do you suppose I figured out that I only had 8 divisions?) everything worked great!! I now have variable speed on my 2" pulley from 0-1140 rpm. If I throw on a larger pulley, I can easily double or triple that max speed. I don't know about a 6" chuck spinning around at hyper RPM's. It kinda scares me.

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    Now my lathe is ready for the CNC portion. I have already ordered ballscrews and stepper motors. On my vacation, I doodled on my MacBook and designed what I think is a very workable conversion. I need to redraw that in Visio. (I don't have a cool 3D CAD program like Solidworks) Then off to Dolphin for the CAD and CAM portions. I think I'll actually wait until I have ballscrews and steppers in hand before I finalize the design. You never know where a wire might come out of...Do ballscrews have wires????



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    yup

    YES the ballscrews have wires...one power 110 volts one negative...lmao
    nice job...and brainfarts are my forte.............

    keep up the great work...........



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    Oh yeah

    I almost forgot....1. thats a damn nice vfd setup and shroud cover you built...geee i might wanna do that and start ripping mine apart....you got plans and drawings?...hmmm???

    Also be advised i spin my 6 inch chuck at the top speeds...no problems, other than the visual one that you think the whole damn thing is going to go airborne.....

    looky at my pics...lettin her rip and that chunk of bronze is as big as the chuck.....no worries mate.........

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    Bodysnatcher,

    Thanks for the compliments

    This morning I set off to replace the straight arbor in the one of my ebay Albrecht chucks with an MT2 arbor. Boy that sucker was on there good. Not actually having the proper tools for this job, I tried wedging, pounding, pulling, prying and praying to get it off. Finally hit the internet and decided I needed to take the chuck apart to remove the arbor. So I clamped the old arbor in a vice and used a strap wrench to try to unscrew the hood. Lo and behold, the arbor spun right off the whole chuck. Cleaned everything up good, stuck the MT2 in the freezer and put a heat gun on the chuck. One swift hit and hopefully the new arbor is there to stay. Then I realized that the new arbor was so long that you could not retract the tailstock fully. So I chucked up the Albrecht and parted off about an inch from the end. Now it works great!

    Also, just for fun I swapped out the 2" pulley on the motor for a 4" one then used the smallest pulley on the spindle. The spindle turned at north of 3500 rpms at 120 Hz! Nothing flew off and impaled me, so I guess it's okay. Is there any practical use to spin this quickly? Will it torch the spindle bearings?

    Bodysnatcher...Glad you like my VFD enclosure. I actually just built a cardboard mockup and then transferred that to 1/8" aluminum. Used a HF 30" sheet metal brake to make the bends and then cut the sides to fit. I can take some measurements and more pictures if you like, but I don't have any CAM files or plans. Just let me know



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