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  1. #1
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    Default 7 x 10 project started

    Here's my recent progress in the past week or so.
    Motor mounts are done, and next up is a few purchased parts. Need a couple timing pulleys and a belt, and a split collar to clamp the screw on to the motor shaft.
    I'm using the original cross-slide screw assembly (for now, anyway), and a 3/8-10 acme screw & delrin nut for the Z axis (that IS what you lathe guys refer to as the Z-axis, right? Pardon my ignorance, as I'm primarily from mill background).

    One of the criteria for this project (other than low-budget) is that I didn't want to grow the footprint of the lathe excessively, and it looks like I've accomplished that so far. I'm extremely happy with the motor mounts. I will lose about 1/2" travel from mounting the motor this way. I can definately live with that.

    So far the only permanent modification to the lathe is 4 m6 tapped holes in the back of the bed.

    MACHINED MOTOR BRACKETS, READY TO PUT TOGETHER


    STRIPPED LATHE, READY FOR THE NEW MOTOR MOUNT BRACKETS


    NEW MOTOR BRACKETS & MOTORS INSTALLED




    Similar Threads:
    Last edited by blades; 06-09-2009 at 10:28 AM.


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    Registered Teyber12's Avatar
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    wow that looks really REALLY good! the z axis is a dual shaft right?

    keep up the good work and nice pics on the machine



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    Thank you Teyber! And no, it will be a single shaft setup.
    More pics forthcoming when I get more done on it.



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    Blades-
    That does look good - very compact. I think that Teyber was trying to say that the Z axis motor must be a dual shaft motor, and that you will be connecting the lead/ball screw to the second shaft on the back of the motor.
    I have worked out a deal and should be getting a 7x10 lathe very soon, and I am intersted in following this thread to make modifications in the same manner. Would you be willing to share models/drawings of the parts you have designed and made so far?

    Have you thought about limit switches? You may be able to hide the Z axis limit switch inside the block that mounts to the X axis - and have a plunger poke out both sides of that block that would touch the headstock housing at one end of travel and the Z axis motor at the other end.

    Also, you could get back the last 1/2" of travel if you made a spacer that mounts between the bed of the lathe and the motor mounting plate.

    One thing you may need to watch for is backlash on the Z axis - most stepper motors don't have thrust bearings on thier shafts, they use a wave washer to preload the bearings. A simple way to check is to push on the end of the shaft by hand on the mounting flange end - if the shaft moves in, you may have an issue when your screw is clamped to the shaft.

    Keep up the great work.

    Keith



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    Hey Keith, thank you for the comments. I believe you're right, I misunderstood Teyber's question: yes, it is a dual-shaft motor (some days I'm really slow...).

    You are right about adding a spacer block to the back - good idea. I will leave it as-is for now, and address that issue if I ever need to. I haven't looked at limit switches yet, but I will have to pretty soon.

    The motor seems to have no perceivable shaft end-play, as this is one of the first things I looked at when deciding how to drive the screw. Apparently, these motors have a decent thrust bearing setup. For a couple reasons, this setup will be acceptable. If this were a larger lathe, such as a 8x12 like Teyber has, I would not load the motor thrust bearings like that, I'd have the screw set up with it's own thrust bearings. I don't anticipate any heavy cuts with this lathe, and I'll only be cutting soft materials with it. Plus, my lead nut is delrin, so that won't take a lot of abuse itself. This all plays into my "low-budget project" to help keep costs down and still be reasonably solid.

    The crank handle was removed from the cross-slide and attached to the z-axis motor, likewise the crank handle was also removed from the compound slide (which I won't be using anyway), and will go back on the cross-slide, allowing full manual useability (except for threading, of course). Some time ago, I replaced the compound slide with a solid block for added stability.

    Absolutely I will share anything I have regarding construction information and drawings. I started out with hand-sketched drawings and built my parts from there. I do have an AutoCAD file of the 3 main parts, but nothing is dimensioned or called out. I've gotten really lazy when it comes to modeling or full drawings.

    I ordered my timing belt & pulleys today. Only modification to those will be to open up a 3/8 hole in one of the pulleys to 12mm to fit on the x-axis screw.

    Keep us posted as to when you get your 7x10!
    I originally had no intentions of CNC'ing this lathe, but I sold my X-2 mill (which was my previous low-budget conversion project), and almost immediately started planning a retrofit for this lathe.



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    Default A few suggestions...

    Your build looks really clean. I know you said you don't want to increase the footprint, but there are 2 things you can probably do to get a bit more travel out of it without adding much to the footprint...

    First, I like how you did the Z axis, but have you thought about making the end-of-bed plate a little longer and putting the motor on the other side of the bed? You could run the lead screw out like it was (or longer if you were planning on upgrading) so it sticks out of the end, put a timing pulley on it and run a timing belt to the motor, mounted on the other side of the bed. This would get you travel all the way to the end of the bed instead of taking, what, about 3-5 inches out of the envelope by putting it where you have it? You could put the hand crank either on the end of the lead screw or on the front side of the pulley if you didn't mind cranking the thing from there.

    Second, there is a mod out there somewhere (I think its in one of the Yahoo groups relating to the mini lathe) that lets you add another inch to the X travel. All it requires is that you mill out a bit more of the clearance in the saddle for the X axis and mill a small block (about an inch deep) that mounts between the saddle and mount for the dial. It allows you to use the lathe to cut on stuff another inch or so in diameter than how its currently set up.

    Lastly, any chance of seeing a few drawings of what you have so far?

    -Farasien



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    Actually, one of the first options I looked at was what you suggested: mounting the motor on the back side (under the chip tray) and run a timing belt setup. This was looking like a pretty good option, but I opted for my method due to it being more simplistic (albeit at the cost of limited travel).

    Like I was telling Keith, I would be glad to share my drawings, but they are incomplete, lacking any dimensions or callouts. The are, of course, drawn accurately though, so dimensions could easily be pulled off the drawing. Given the opportunity and time, I will dimension them.

    Funny, I used to be a tool designer for a living, and was very demanding of my own work. I'm really getting lazy (or maybe just too busy).



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    Registered Teyber12's Avatar
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    good to be busy in this climate



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    I ended up having some time to kill at work today, so I detailed the CAD drawings. Note that I have also attached a .DWG and .DXF files as well. The .DWG file is AutoCAD 2006.

    I would encourage anyone following this project to take liberties with it. Like Farasien mentioned, the Z-axis motor could very easily be mounted on the back side of the lathe (under the chip trap), and utilize a timing belt setup. I was so close to doing this, but then decided to go with how I did it to simplify things (for what I'm going to be doing with it, I won't be missing any lost travel). Also, if you're not concerned with keeping a small footprint, you could easily use this same plate and mount the motor to the other side, thereby losing no travel at all, and still keeping it simple.

    I will include more engineering data once I pull it off my sketches. Will also include info regarding purchased parts.






    Attached Files Attached Files


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    I picked up my 3/8" shaft collar today, so I attached the screw to the motor for try-out.





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    Default Quick ?'s for you...

    I was looking at the photos you had posted for the parts and the drawings, but don't see how the ballscrew nut plate attaches to your assembly- does it get put onto the side of the carriage block somewhere? Just wondering, because I didn't see any holes on the carriage block drawing for it...

    Secondly, what are the specs of the ballscrew you have and, if I may, where did you get 'em? McMaster Carr?

    -Farasien



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    Not using a ballscrew, it's a standard 3/8-10 LH acme screw. I did look into using a ballscrew, but opted to go with the acme screw because of price and simplicity (would love to have used a ballscrew though). Got the screw and delrin nut from user widgetmasterinc on ebay. Here's a link to the nut: LINK
    The same seller also sells an 18" section of 3/8-10 LH acme threaded rod for $10.
    It wouldn't be very difficult to adapt this design to use a ballscrew though. Would probably require some type of side plate off the Carriage Block.
    Here's a pic showing the mounting of the nut. This pic also shows where the Lead Nut Plate is utilized.





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    Got a lot more done yesterday! My timing pulleys & belt arrived on Friday. This pretty much concludes the main assembly of the components, but I still have a good ways to go. Need to mount limit switches, as well as an optical gate to use as a rev counter on the spindle (used for threading).

    I ended up modifying the cross slide screw retainer by machining .140 off the face, which was necessary to allow more room for the timing pulley. I also turned down the end of the cross slide screw shaft to .375 to accept the timing pulley.

    Not shown in the pics, I also drilled & tapped 2 M6 holes to utilize one of the original lead screw support blocks. The block is now mounted on the far end of the lead screw. I had to make a .510" thick spacer to go behind the support block. I still also need to make a brass or nylon sleeve to go between the 3/8" lead screw and the 12mm bore of the screw support. Note also that I borrowed the handle from the compound slide to put on the cross slide. No modifications necessary, as the bores of the 2 handles are the same.

    This portion of the conversion project has gone pretty fast, but future progress will probably be a bit slower. Will keep posting progress as it's done though.








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    Nice work. I'll definetly be using some of your ideas, if not duplicating your parts.:-)
    I'll be getting the 7x10 lathe this Friday, and I intend to take it work. Given enough lunch hours, I can duplicate what you have done. I'll just use it manually until then.
    I'm not so sure that my stepper motors have good axial backlash properties as your did, but I can always upgrade thier bearings to angular contact and preload them with stronger spring washers from McMaster Carr. I think that I may have ballscrews small enough in my ballscrew collection to fit in the cross slide for the X and along the Z axis as well.
    Did you bore a hole in the end of the acme screw and slit it, then clamp it over the motor shaft? Do you have a support bearing at the opposite end of travel, or are you rotating this so slowly that you aren't concerned about whip?
    BTW, where did you order the timing pulleys from and how much did they cost?
    Keep up the good work.
    Keith



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    Sweet, bet you're really looking forward to Friday! :-)
    Did you bore a hole in the end of the acme screw and slit it, then clamp it over the motor shaft?
    That's exactly what I did. Although "bore" is a bit flattering. I merely double-drilled it to .250, which is basically to drill it 15/64 and use the 1/4" drill as a reamer. Then I carefully split the end with a hack saw, and used a 3/8" shaft collar to clamp it. The other end is not yet precision supported, I still need to make a 12mm o.d. x 3/8" i.d. bushing for it, to take out all the slop and make the end support a bit closer tolerance.

    Since your lathe will be brand new, you may want to consider buying the replacement parts at LMS so you don't have to modify the original ones. That being said, I did not. I just modified what I've got, taking note of the replacement part costs so I'd know up-front what I was looking at.
    Here's the P/N's from STANDARD DRIVE PRODUCTS

    I have listed below to use a 55 tooth timing belt, but I would recommend a 56 tooth if you build my design verbatum. The motor could stand to be .100 lower, as it now touches the bottom of the acme nut. That extra tooth would drop it down enough to have some breathing room. Optionally, the top of the delrin acme nut could be machined down. But if you already have ballscrews to use, your results and stackup will differ from mine anyway, and this would be a non-issue.

    ================================================== =

    Part Number A 6A 3-20DF03708
    Unit Inch
    Pitch .200 (XL)
    No. Of Grooves 20
    Material Aluminum Alloy
    Belt Width 0.375
    Bore Size 0.250"
    Flange & Hub Configuration 2 Flanges / With Hub
    Pitch Dia. 1.273"
    Outside Dia. 1.253"
    Overall Length 0.875"
    Hub Dia. 0.94"

    1 to 24 $11.31



    Part Number A 6A 3-20H3712
    Unit Inch
    Pitch .200 (XL)
    No. Of Grooves 20
    Material Aluminum Alloy
    Belt Width 0.375
    Bore Size 0.375"
    Flange & Hub Configuration 2 Flanges / No Hub
    Pitch Dia. 1.273"
    Outside Dia. 1.253"
    Overall Length 0.563"
    Hub Dia. 0.00"

    1 to 24 $11.11

    TIMING BELT 200XL - 55 TEETH (was around $5.00)



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    I'm a bit spoiled actually, I already have a well equipped shop at home, and this is a machine that I'm going to use at work. I have access to a prototrak there, but no lathe. I'm bartering some stuff for it, and it's used, so I'm not sure what condition it's in, so it will be a surprise on Friday. We'll see. I'll modify whatever I need to, as I'm not concerned about it remaining stock. I'm glad to hear that there are so many replacement parts, as I may need to order some/make replacements to get it functional in the first place.

    Thanks for the info on the belts and pulleys. I'll probably need to use even a longer belt, as the ball nuts are a but larger in diameter, and I may need more clearance. I have some optical triggers if you want a few, let me know and I'll mail them to you. A friend of mine used one on his 9x12 import lathe, and he controls it with Mach3 and does threading with it.

    Keith



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    Thanks for the offer on the optical trigger. I did buy one, but I'm not sure how to go about hooking it up yet.
    I do have an extra X-axis motor bracket setup if you want (free, of course. It's not nearly as nice looking as what I've got pictured here, but it's dimensionally identical. I tried to utilize a motor bracket left over from my mill project. I decided it wasn't asthetically pleasing enough, so I made a new one (the one in the pics here). The actual motor brackets are 1x1 steel angle, and you could easily make new ones to accomodate the longer distance required for your ballscrew. The aluminum block that mounts to the carriage is decent looking 1" thick alum. like the one here, except it's more of a T shape because of the type of motor brackets used with it. I can probably email you a pic of it tonight if you want to have a look at it. Would be glad to trade it for an extra optical trigger.



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    Default spindle timing

    Nice looking build,
    I am the guy Keith mentioned with the 9x20 converted.
    I used a magnetic switch Keith had given me and added 2 tabs to my spindle. I put the switch under the front nameplate on the headstock. I drilled straight through the spindle (as straight as I could with a hand drill) Tapped the 2 holes and made up 2 sheetmetal tabs. 1 tab has to be smaller than the other for Mach to recognise there are 2 tabs. The wiring diagram I found some where on the web and if I can find it again I will post it for you guys. I have been using this lathe for ~ 2-3 years now I think, the timing sensor has worked great. Here are a couple of pix for ideas.

    Cutmore

    Attached Thumbnails Attached Thumbnails 7 x 10 project started-timing1-jpg   7 x 10 project started-timing-tab-jpg  


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    Hey cutmore, thank you for the pics. The plot thickens! From the limited bit I've read about spindle counters, they only used 1 tab and 1 gate. Didn't make a lot of sense to me though, as I don't see how 1 light break per rotation could be accurate enough to allow threading. This is my first rodeo with converting a lathe, so I am counting on the knowledge and help of people (like yourself) who have been down this path.

    - Bill



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    Default Spindle counter

    Hi Bill,
    No plot to thicken here! Once you hook up the sensor, in Mach 3 you calibrate the spindle and Mach3 automatically recognises how many slots or tabs you have. It really is easy. I will try to find the diagram tonight.

    regards,
    Cutmore



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