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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > a couple 7x14 lathe conversions
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  1. #1

    a couple 7x14 lathe conversions

    One picture is the one that arrived today , the other is one arrived friday and I quickly converted on the weekend . Basically everything was done with a drill press or and hand drill , aside from milling the cross slide . I didn't get fancy and I cut and winged it as I went along . I may do something down the road to lighten the look of it and make it not so blocky , but I only care for it to function than to look pretty
    When you don't have bluing spray for layout then fast dry black does the trick

    Overall there aren't many hours into it and it's performing exceptionally well . The 570oz motors are probably overkill for what it is but thats what I had on hand . I've set it up to use linuxcnc since my emco lathe is running it to . The rapids are set low at 60 ipm which is quick enough on a small lathe like this . Linuxcnc has been installed on an old windows 7 hp thin client that was previously being used on an x2 mill .

    I've been going hard on the emco and with production levels spiking I needed another solution . I have parts that I run which need to be held within .0005" on the od , and considering the stick out it would be enough challenge for an industrial lathe not to chatter . I've done a lot of program tweaking to get the emco to hold sizes with a good finish . Yesterday I dropped the critical program on the conversion and it held sizes all afternoon with an exceptional finish . There was a bit of creeping over time but it's to be expected on any lathe holding a tight enough tolerance .

    Overall I'm impressed . I'll break down the first lathe and trace all my parts for the second one . The factories don't know what deburring is and the slides need a good cleanup , then after that they are smooth .
    For now the last thing I will do is some grinding on the casting under the z motor mount to square it up a bit better . I left the ballscrew on the x a bit on the long side since I may want to get a bit more movement from the slide , time will tell

    Btw all this was done with what was at hand at the time , some bolts need to be replaced with proper sized cap screws . Also cop keyboards are awesome in a shop , you'll see that in the pics as well . They are expensive but can be found on ebay for pretty cheap

  2. #2

    Re: a couple 7x14 lathe conversions

    I had the shop spacing really nice for the mills , but the mills are getting squeezed closer together . I need to move the lathes from the other side of the shop into the machine room . Mills on one side , lathes on the other . I'll need to get some plywood to build some proper stands for the 2 new lathes and move the emco in there as well . The mill area still needs some tweaking , better organizing , and a serious cleaning . It's a mini production shop and they get used so much that keeping up on cleaning isn't so easy .
    My wife believes I can't do 2 things at once , she's never seen me in the shop .

  3. #3

    Re: a couple 7x14 lathe conversions

    One mod I can see coming is to the retainers for the saddle . When it's tight it's tight , except there is nothing to lock the bolts in place which have worked their way loose . Studs and double nuts will resolve this for the time being and hopefully will be good enough moving forward . Otherwise I'll turf those retainers and come up with something better . I see a lot of guys make brass retainers , brass is very abrasive so I'm doubtful that I will follow that route . My compact 5 has delrin strips under the retainers which was cringe worthy when I saw that but they've proven themselves , so I may come up with something similar

    The screw for the motor pulley also worked it's way loose . I went to tighten it and the threads were stripped . That got tapped to a 6-32 which is a bit more coarse and is holding well now . a back up pulley is on order .

    This build was quickly slammed together and I expected some tweaking moving forward , or something I may have over looked . The castings are good aside from the burrs that had to be removed , and lathes are so basic that upgrades are easy enough if or when needed . As it stands it cuts well and holds sizes well , theres around .0005 backlash which hasn't been compensated for in the software and at this point it's having no ill effect

    I was running a program last night which would lose steps on the x at the exact same rapid moves each time . This is a proven program so there was no obvious reasoning for this , I looked at that portion of code over and over again and it was perfect . It had me beating my head off the wall , especially since it's been running other similar programs without issue . I changed drivers , looked over the electrical and couldn't figure it out . I tweaked the base period , acceleration and a few other things and it ran without a hiccup . I'm guessing I was sitting on the borderline of what this setup can handle . Regardless , there are no noticeable changes to the performance

    Something to be careful of with these lathes is to be sure that cuttings aren't working their way into the control . There was a review that pointed to this issue and the guy burnt his electronics . I watched as swirls worked their way towards the hole where the lead screw goes through . I temporarily cut a piece of neoprene to fit and keep the crap out of the control . My eventual solution was simple , mount the control to the wall rather than on the lathe .

    Chip containment is also a must have , which hopefully comes sooner than later . I've got shavings flying half way across the shop , and getting a face full of swarf sucks .

    Another thing I need to do is connect the motor to the relay on my breakout board , it's there so I may as well be using it

    When it comes to software , linuxcnc has mach beat hands down . I started with a mach install and after 45 minutes I had enough with that stupidity and went straight to linux which I should have done from the get go . Mach is great for mills but the lathe is terrible , it's a lathe , all those screens are unnecessary clutter

    The second lathe is still sitting because I've been too busy to get to it . I'll have to set aside a day to go at it and get it running . I'll post some pics as I go along this time around . There's nothing exciting about square chunks with through or tapped holes but someone may find it useful
    I've got some brand new nema 34 motors which I was going to use on a g0704 but I think I'll let that mill finally have it's death . I may toss those motors on just to get some use out of them , otherwise it will get the same motors the first got

  4. #4

    Re: a couple 7x14 lathe conversions

    another point with these lathes is that the chuck jaws need a cleanup as well , otherwise they'll gouge the parts

  5. #5

    Re: a couple 7x14 lathe conversions

    Second is pretty much completed aside from some work to mount the drivers and route the wiring . With a 36v supply I went as high as 150 ipm and didn't test beyond that . I cut it back to 90ipm where it will stay
    . I'd rather have added nema 23's but I needed to get some use out of the shiny 4.5nm 34's that have been sitting from another project . I followed what I did on the first lathe but rather than exact copy every part they were drilled and fit as I went along . A few parts were made to match the other but I really didn't want to tear it down to get some measurements . Overall it went fast and easy .

    If this one stands up as well as the other then I will be happy .Adjustments are always a regular thing with any of these cheap lathes and mills . My x2's always needed adjusting until I pulled the set screws and added 10-24 bolts with lock nuts . This reduced the need for adjusting a lot and these lathes will see the same change real soon for the dovetails

    Summer isn't as busy of a time for me , so I'll probably rethink both setups then do them a bit more proper , rather than a hack job which it is . Even still , hack job or not they are solid and they will get the job done
    One quick mod which is on the way is breakers to replace the fuses , I hate fuses

  6. #6

    Re: a couple 7x14 lathe conversions

    I have to correct myself on the screws I used on the x2 mills , they are1/4-20 cap screws with lock nuts . the lathes are smaller and they'll be 10-24 as mentioned

  7. #7

    Re: a couple 7x14 lathe conversions

    I've never read much good in relation to those cheap wedge style tool posts . Except how bad can they really be , so I bought one , Bad , just plain bad .
    I wasn't overly worried about repeatability but the chatter I was getting had me looking in all the wrong places until I put the original post back on .

    This second lathe is cutting ok but I'm getting backlash on the x , I can compensate for it but I want/need to eliminate it . I find that some of the ebay bearing blocks are bad for this and I'm going to swap the block tomorrow . I'm pretty sure I had some better bearings that I bought to replace the ones that come in the blocks , so I'll have to try to track them down . As it stands I can easily use it for secondary ops which are more aesthetic than functional at +- a few thou , but I want it to perform as the first one does

    Note to self - Always remember to connect the power back to the bob . I reran all my wiring and forgot to plug the usb cord to the bob . Things appeared to be working , except during a test program the z was working it's way towards the chuck by .1 every pass . I looked over the configs , changed drivers , checked the wires over and over again , then I realized the bob had no power . I've never seen one of these boards turn my motors without power but it did this time . Anyhow that was my dumb move for the day . Sometimes it's the simple oversights that can be a pita .

  8. #8

    Re: a couple 7x14 lathe conversions

    I found the angular contact bearings I bought a while back and replaced the crappy bearings that came in the block for the x . When I had it all apart I realized the gibs were adjusted a bit too tight to which was causing a bit of flex . Those 2 changes made a world of difference and it's cutting as I hoped it would . The rapids were cut back to 60ipm but I'm going to put the z at 100 , and the x is fine where it is at , otherwise faster would be a bit overkill for the short distance it travels

    Overall I'm happy with the way they turned out and they'll be a great addition to the shop . I've got encoders on the way so that I can run them properly at feed per rev vs ipm . Plus it'll be handy if I need to do any threading
    I'm not sure how much life a guy gets out of the spindle belts but they are cheap priced and I have extras . Thats something that may get replaced with something better if needed

    I did a short vid of a test run , it's turning from 5/8 to .3 and 2.3 deep on the z . A higher rpm would be nice but it is what it is
    my phone doesn't appear to like the close motion and/or the chips flying so it blurs at times . A spring pass gives a nice finish and the parts hold their sizes well


  9. #9
    Join Date
    Oct 2009

    Re: a couple 7x14 lathe conversions

    Very nice work. You almost have me convinced to go out and buy a 7x14 lathe just so I can do a CNC retrofit.

    I already have a Grizzly G0602 10x22 lathe, but those little guys are so cute.

    It looks like you are controlling both lathes with LinuxCNC? Was this your first LinusCNC experience or had you used it in the past? Any external motion controller?

    How much do you think you have in the bare lathes and how much for the conversion?

  10. #10

    Re: a couple 7x14 lathe conversions

    I've used linuxcnc on a router way back when it was still emc but crossed over to mach shortly after . When I bought my emco compact 5 a few yrs ago I saw a post from Samco showing how he was able to get his working with linuxcnc and without any butchery of his electronics , something that has to be done if attempting to run the compact with mach . I used his files and was up and running in no time .

    All 3 are running off parallel ports . The emco is running on a dell small form factor and the 2 new ones are running on hp thin clients which have 16gb flash drives .
    I tried mach 3 but it's pretty bad for it's lathe portion , linuxcnc is pretty straight forward and easy to use and modify if needed .
    I always liked mach for my mills but after getting my tormachs I quickly loved pathpilot and even my torus pro was crossed over to it to . Running on linuxcnc is so smooth .
    Overall linuxcnc is easy to setup with the wizard and it only takes minutes to get it setup and have a machine running . If you want to run though a mesa card then thats easy enough to setup while using the config wizard

    Both lathes cost $900cad each shipped . As far as the rest of the bill goes I can't recall cost , I've had all these parts sitting for quite some time .
    To break it down , 2 ball screws 1 ballscrew block , 2 motor couplers , 2 bk12 bearing blocks , steppers , drivers and bob , 2 encoders (still waiting on) .

    Plus some flat bar , 3x1/2 4x1/2 and the 3x4x3/4 block which bolts to the carriage and is the key component to the whole thing . That 3/4 block holds the z ballscrew block , and the mounting for the x gets bolted to it as well . If that piece is drilled and tapped right then everything else should fall into place . The side mounting plates easily could have been 1/4 thick but I used what I had on hand and didn't disturb my mills for frivolous work .
    The only thing I stopped one of my mills for was to machine the cross slide for the needed room for the ballscrew

    First thing I did was mount the bk12 for the z right over the flat where the stock screw block was . I slid a 5/16 drill between the bottom of the way and the top of the block to gage the bk12 height . I added the ballscrew with it's store bought mount block , lined it up the best I could then traced most parts from that point on . It helps to go a bit bigger on the through holes which gives a bit of wiggle room to make any adjustments

    The nema 23 motors add a fair amount of weight on the front which makes it a bit tipsy while putting it together , the 34 motors really added to that . After getting them together they got bolted to the table

    this is a pic of my lathe dept lol . I used what plywood I had on hand so it's not exactly uniform or pretty but it keeps them separated and the chips somewhat contained . I still need to clean up and get the wires a bit more under control and cleaner looking . The picture goes to show the difference between nema 23 and 34 , it's significant

  11. #11
    Gold Member
    Join Date
    Feb 2009

    Re: a couple 7x14 lathe conversions

    Did you CNC the spindle or just the X and Z axes?
    CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html

  12. #12

    Re: a couple 7x14 lathe conversions

    I'm just using the stock motors and the hand control for the speed . I've got encoders on the way to get the spindles to sync with the software but thats about as far as I think I'll go with the spindles , aside from connecting them to the on/off relay on the bob's

    None of them have home switches either . The only times I'd need them is on power up , and it's so quick and easy to set a part that I'll probably never bother . For the most part they'll probably sit idle rather than shut down anyhow

  13. #13
    Join Date
    Oct 2009

    Re: a couple 7x14 lathe conversions


    Thank you for the detailed info on how you did the conversions. Very nice work.

    I’m a little surprised that the 7x14’s cost almost a grand? I see several 7x14 mini lathes under $500 on eBay with free shipping?

  14. #14

    Re: a couple 7x14 lathe conversions

    I've looked at those . usually the ebay lathes cost a couple to 3 hundred to ship , at least to here in Canada . The 900 ea are Canadian dollars , which works out to 650us .
    I weighed out the options and going through amazon was definitely the lowest cost option for the 7x14 lathe , especially with the free shipping on top

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