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Changing Gears On 7x14 (g0765) Lathe [solved!]

Discussion in 'MINI-LATHE & MINI-MILL INFORMATION' started by MagicSmoker, Nov 18, 2016.

  1. MagicSmoker

    MagicSmoker United States Iron Registered Member

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    My 2nd post after lurking and reading lots of books, watching lots of youtube videos, and sifting through threads here and elsewhere the last couple of months. I have very little practical experiencing with machining, but I'd like to think that all the reading and video watching I've done has made me "book smart" about it (that said, my day job is an electronics engineer, so I know all too well that reading about something is not a substitute for doing it).

    I've done some facing, turning and center drilling so far and am learning some valuable lessons in the process. For example, I don't think I am ever going to get proficient at grinding tool bits, so I ordered a set of indexable tools from Amazon. Also, I can now see why quick change tool posts are such a popular accessory...

    But the one thing that has me really stumped is how to remove the various gears to change the threading pitch without using what I feel to be excessive force (the manual just says you might need to use a screwdriver to pry the gears off if they are stubborn...). More specifically, I can't figure out how to remove the metal "A" and "C" gears from their keyed bushings. Changing the "C" gear is less of an issue because I can just buy another keyed shaft ("bushing" in the parts list) and install a 60t plastic gear on it - which is the only other choice I figure I'll need - but not all of the parts are available to make up extra "A" gear assemblies so I have no choice but to figure out how to get that durned gear off the keyed shaft. Any tips from fellow 7x14 lathe owners (my understanding is they all use the same change gear setup)?
     

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  2. MagicSmoker

    MagicSmoker United States Iron Registered Member

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    Of course I also emailed Grizzly about this and their response was to use mineral spirits to remove excess grease and debris and that would somehow magically make the gears easier to remove. Uhh... I'm thinking I'll need to use an arbor press to remove the gears from the keyed shafts; a little mineral spirits ain't the solution, then.
     
  3. tweinke

    tweinke United States Active User H-M Supporter-Premium

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    Sounds Ike a bit of strategic polishing is in order.
     
  4. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Remove the gears and check the gear without the key. It should be a snug fit but remove easily. My HF 7x had a problem with the key/key slot. A little bit of work with a file and some 400 grit wet or dry paper and everything slides off and on easily.
    These little lathes are more of a semi finished kit than a ready to work solution.

    Roy
     
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  5. MagicSmoker

    MagicSmoker United States Iron Registered Member

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    Hmm... it seems I did not communicate my problem clearly enough: I can't figure out how to remove the metal gears (i.e. - "A" and "C") from their keyed shafts in the first place without using methods that I feel will apply more force on the gears than they are likely able to withstand (e.g. - pushing out the shaft with an arbor press).

    After searching youtube for videos on 7x14 change gears I found one where the A gear slides right off; further evidence that my A and C gears are abnormally tight. Not being able to remove the C gear isn't a big deal because I can order all the parts necessary to make up another B/C gear assembly (and I did just that), but some of the key components of the A gear assembly aren't available (e.g. - #48 - gear mount) so I won't get a second chance if I break something trying to remove the A gear, nor can I make up a second assembly with the 40t gear permanently mounted for extra convenience.

    Of course the nuclear option here is to send the lathe back to Grizzly, but I'd really rather not do that because everything else on it appears to be in good working order - which I understand is not always the case - and I spent a lot of time disassembling, cleaning and reassembling all the various moving bits.
     
    Last edited: Nov 20, 2016
  6. juiceclone

    juiceclone United States Active Member Active Member

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    heat applied to the gear will expand it's circumference, which will make the hole bigger and gear easier to remove.
    .....usually.....:>)
     
  7. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    " Hmm... it seems I did not communicate my problem clearly enough:" You did communicate your problem very clearly. I just failed to understand the magnitude of the problem.
    I used 2 screwdrivers as wedges to initially separate the gears from the keyed bushing. I do have an arbor press, however the force needed was not excessive and did not require an arbor press. However an arbor press would work fine if needed. Those gears and bushings are very tough. If yours are so tight that they will be damaged by separating them you should call Grizzly and ask for new parts. They are pretty good on service problems. Also all of the parts needed to make the the assemblies are available at Little machine shop - http://www.littlemachineshop.com/default.php. I don't know if you have used LMS before, they have every oem part at reasonable prices and fast shipping. Great people.

    Roy
     
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  8. MagicSmoker

    MagicSmoker United States Iron Registered Member

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    After I read the post to heat the gears up, but before I saw your response, I said screw it and put the C gear assembly in the mighty 1/2 ton HF arbor press and ended up having to crank down pretty hard on the handle - at full extension, no less - to push the keyed shaft out of the metal gear. Flush with my success, I next used the arbor press to put in the wrong gear the wrong way, then the right way, then the right gear the wrong way, then finally the right way. So, I got a lot of practice with changing the gears...

    I then felt semi-ready to tackle the A gear, so I unbolted the whole gear assembly, removed the snap ring, and then popped the assembly metal gear down in the arbor press and pushed out the stepped, keyed shaft from the plastic gear that mates with the tumbler gear. With the stepped/keyed shaft in hand it became abundantly clear why my prying was unsuccessful: I was prying against one of the steps in the shaft, rather than between that step and the metal gear. Still, it once again took considerable force with the arbor press to push the metal gear off the shaft so it is unlikely I would've been able to pry the gear off with a screwdriver. Also, that step in the shaft required I get creative with how to support the metal gear for the press to push against; I ended up using the flat side of my pry bar on one side and an 8" mill file on the other; they were both the right thickness and being hardened steel would deflect less from the press.

    The end result: I finally managed to cut my first thread with a lathe! It looks kind of ugly and the threads aren't symmetrical about the crest but each pass of the bit tracked the previous one and I was able to clean the threads up with a die so I'll call it a success.

    G0765-A-Gear-2.jpg G0765-24TPI-1.jpg
     
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  9. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Congratulations! For your first ever threads that looks great. You will develop your own technique that will give successful results as you cut more threads. Very good that you got the gear problem figured out and working now. It is sometimes difficult to grasp the problem when one does not have the machine to touch and beat on. There is a wealth of information on this forum and at minilathe.com. There are so many mods for these little machines that you can spend the majority of your free time upgrading them. All metal gears, tapered roller bearings, are just a few of the common upgrades. Feel free to ask and more importantly let us know what you learn and do. We all appreciate what you contribute. Welcome to the forum.

    Roy
     
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  10. juiceclone

    juiceclone United States Active Member Active Member

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    did I read correctly?? why did u press the new gears back on?? they are supposed to be easily removable ...either the shaft(s) or gear(s) need a little adjustment.
     
  11. MagicSmoker

    MagicSmoker United States Iron Registered Member

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    Yes, and that was part of the problem! Everything I read and all the videos I watched suggested, if not outright showed, that the gears should be easy to remove, whereas mine - especially the metal ones - weren't coming off without a fight.

    Now that I've swapped out several of the gears a few times they are taking much less force to get on/off their shafts, to the point that I can change out the plastic gears by hand; the metal gears still need to go into the press, I just don't need to crank down on the handle so hard. More specifically, it appears that the shaft bore on the metal gears, at least, is a little bit undersized and the keys are a little too tall (or the keyways are too shallow). Once I have some spares on hand I might try reaming the metal gears with an 8mm spiral flute reamer and grinding a few thou off the keys (once I figure out how to securely hold onto the durn things against either the bench grinder or the belt sander).


    Yes, you read correctly, and yes, it does appear that the gears are an unusually tight fit on my machine (in contrast to the unusually sloppy fit of the compound slide, but that is a subject for another thread). It will be interesting to see if any other new 7x lathe owners experience the same issue or if mine was just a one-off.
     
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