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  1. #1
    Gauge is offline Aluminum
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    I have a Craftsman/Atlas 12" Lathe - Model number 101.07403. Mine has the manual gears. Anyway, I found someone selling a quick change gear box for an Atlas 12" lathe, but the seller says it fits an Atlas 12" Model 3990 Lathe. Would this gear box fit my lathe? I don't even know if a quick change gear box can be fitted to my machine, but I think I remember someone on this site telling me to keep my eyes open for the QC gearbox because it's very easy to install and MUCH easier than swapping out gears.

    As always, I appreciate the help. Thanks!

  2. #2
    Steve Steven is offline Aluminum
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    I don't think it will. A 3990 is a completly different lathe, not origionally built by Atlas. I can't remember the name, but Atlas bought the company and their line of machines and rebranded them as Atlas.

    Steve

  3. #3
    L Vanice is online now Diamond
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    Both Sears and Atlas used to sell the QC conversion kit for the 12" lathe. I suppose it was easy to fit if you got all the pieces and had the right model. They said no drilling or tapping was needed.

    Sears sold two different QC kits in the 1960-61 tool catalog. Catalog 99M2014K ($99.95) fit the 101.07403 and many other model 12" lathes, but not the newest underneath drive model lathe that was sold in that same catalog.

    Tony's site says, "Underdrive Model, 24" between centres, screwcutting gearbox (no motor): No. 3990" Tony's site - Atlas lathes

    So, the difference is not clear, but the underneath drive model uses a different QC kit from the older bench models.

    Larry

  4. #4
    Gauge is offline Aluminum
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    L Vanice - Thanks for that info! Is there a part number in that catalog? I would really like to hunt down one of those QC gearboxs. Swapping out gears manually is not that fun. They must be available somewhere.

    Is there any way you could post a picture? If I know what it looks like, it might be easier for me to identify. Thanks!

  5. #5
    L Vanice is online now Diamond
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    The Sears QC kit for your lathe is catalog no. 99M2014K. Tony has pictures of the old and new Atlas 12" lathe QC boxes.

    Larry

  6. #6
    440roadrunner is offline Hot Rolled
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    I just bought a QC box from a memember on here

    I'm not sure if the newer and older series of Atlas is the same, but if you get the right one for your series, it should bolt right on--except

    I BELIEVE I've read somewhere that some of the older Atlas lathes used a smaller lead screw, so make sure your lead screw is the correct diameter for the box.

    The covers don't fit. In my case, I elected to saw a piece out of the lower part of the original cover to clear the QC and use that.

    Also, read the book on the "change gear" and quick change. You'll find that if you keep your old change gears after going to the QC box, you can use at least some of the old gears with the new box to setup special and metric threads. There are at least two gears in the set that you won't have, who knows if you'll ever need them.

  7. #7
    Wornout is offline Plastic
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    Years ago when I still had hair, we had an Atlas that we wanted to convert. If I 'member correctly, the lead screw on the manual gear change is longer than the one on the quick change. If you can get the quick change shaft (I'm also pretty sure that the size/TPI is the same) size, but you would have to check to be sure. Good Luck.

  8. #8
    Forrest Addy is online now Diamond
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    Ir says here in the arrogant machinists code that a machinist can make anything of metal and mechanical in nature fit up to and work with anything. Sometimes it aint practical but a machinist stubborn enough and inventive enough can do some amazing things.

    That said, installing a QC box from one lathe on a lathe of similar size and design is a fairly simple job once the practicalities are sorted out by answering a few questions. Can the box be mounted in the physical space? Can the index train be made to line up with the QC input shaft? Can the existing lead screw line up to and be adapted to the QC box output shaft? Can the index train be ratioed to suit the new QC box?

    Work your way through all these questions and work out a solution for each and the design is done. All you have to do is the machine work and mechanical work. It aint that simple in reality but in theory it's duck soup.

  9. #9
    precision tools is online now Hot Rolled
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    Atlas manufactured several iterations of that lathe. The first was the 9" machine in the early 30's, followed by the 10" machine that was produced from the late 30's into the early 60's. The final machine was the Atlas 12" lathe manufactured in the 60's.

    Atlas also manufactured lathes for Sears, sold under the Craftsman brand. Craftsman lathes were basically similar to the Atlas lathe, but differed in a few respects. One of the major ones is the early Craftsman 12" lathe. It is the Atlas 10" lathe, raised with 1" spacers in the casting. The Atlas and later model Craftsman 12" lathes are quite different. The early bed is 3/8" thick, while the later model is 1/2" thick.

    The later QC gearbox can be adapted to earlier machines, but it is not a bolt on, some modifications will be needed.

    To add to the confusion, Atlas purchased Clausing, and badged some of the Clausing machines Atlas. The 3990 is probably one of these.

    Forrest is quite correct, of course, a QC box with the appropriate dimensions can be grafted on regardless of origin. There was at least one manufacturer that produced aftermarket QC boxes for the smaller lathes, I had a 10" Logan with one installed. The name escapes me.

  10. #10
    440roadrunner is offline Hot Rolled
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    Forrest, methinks you are over-engineering this. There are habitually SEVERAL of these on eFray at any given time, that ACTUALLY BOLT ON to the lathes in question

    Wornout, in my case--which is the same basic model--the lead screw is the same length.


    This one fits the (older) 10" and is uses a different mount. The box you want has two bolts, parallel to the floor, which replace the two holding the "change gear" banjo on the front of the bed

    http://cgi.ebay.com/Atlas-10-Lathe-P...QQcmdZViewItem


    This box is the one I bought from Wayne Johnson on here. One mounting bolt is hidden under the label, which unscrews

    http://www.wayneshome.us/ebay/atlas/qc/atlas_hs01.jpg

    http://www.wayneshome.us/ebay/atlas/qc/atlas_qc01.jpg

  11. #11
    j king is offline Stainless
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    As Forrest said..
    " Ir says here in the arrogant machinists code that a machinist can make anything of metal and mechanical in nature fit up to and work with anything. Sometimes it aint practical but a machinist stubborn enough and inventive enough can do some amazing things."
    Hehehe.Ya I aint right..Here is qc I built several years ago for my atlas.






    It was a fun project at the time.Now I dont have any. [time that is]

  12. #12
    Gauge is offline Aluminum
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    Man - You guys are AMAZING!

    440roadrunner, do you think the one for sale on ebay would fit my lathe? The seller says it should fit the 12" lathe also.

  13. #13
    W. Johnson's Avatar
    W. Johnson is offline Cast Iron
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    The Atlas 399x lathes look like this...


    This one is a 24"cc early late model(it has no leadscrew clutch).
    Some were bench mount with counter shaft/motor mounted to the bench,
    and others came on underdrive cabinets. I've seen a lot of these in
    the last few years, and the Atlas/Craftsman versions are exactly
    the same. Just badged differently.

    Here's the gearbox, w/leadscrew clutch, off of one...


    There are differences in the casting compared to the early model.
    Also the later newer model has a leadscrew clutch, and that means
    the leadscrew is different on that end as compared to the early model.
    Might be a length difference also.

    I've still got the early model bed that the QC came off of I sold to 440 RR,
    and I have a couple of the late model QC boxes. Want me to see if the
    new QC will bolt up to the old bed?

    How much is the one on ebay going for?
    The one in the photo above is available.

    Wayne

  14. #14
    Gauge is offline Aluminum
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    Wayne - Yes. If you could see if the later model QC box could match up to the old bed that would be appreciated. Thank you.

    BTW - how are you guys able to attach pictures? When I try to attach a picture, it tells me I need a URL? huh?

  15. #15
    W. Johnson's Avatar
    W. Johnson is offline Cast Iron
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    Sorry, I completly forgot about doing this.
    I'll do it Friday. I'm writing myself a note.

    When I try to attach a picture, it tells me I need a URL? huh?
    Your photo needs to be hosted on a web server. A lot of people here
    use PhotoBucket. You can also host them on your personal web space
    through your ISP.

    Way down at the bottom of the PM forum main page is the
    Images and Links Forum.
    In there you'll find this post.
    It has all the info you'll need to post photos to PM. [img]smile.gif[/img]

    Wayne

  16. #16
    W. Johnson's Avatar
    W. Johnson is offline Cast Iron
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    ...seller says it fits an Atlas 12" Model 3990 Lathe.
    Would this gear box fit my lathe?
    Yep, and it bolts right up!


    The rear mount...

    This is where your countershaft mounts.
    You'll have to make a longer stud to mount the rear of the qc.

    Top of qc is about a 1/16th above bed.

    I don't think this matters. It is a little high on its original bed.

    One other difference between early and late models is this
    mounting hole through the bed on the late model qc.


    The leadscrews.
    Late model on top, early model on the bottom. This is the qc end...

    Easy to make that work.

    The other end of the leadscrews.
    Again, late on top, early on the bottom...


    Looks like the hardest part is modding the leadscrew.
    You got a hacksaw and a file?

    Wayne

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