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Thread: I bought my first lathe!

  1. #1
    Neglected Bike Adopter
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    I bought my first lathe!

    I'm quite excited and wanted to share with you folks. After years of Internet videos and reading I have finally taken the first big step into becoming a hobby machinist, and bought a small green drehmaschine!

    IMG_20220108_2200421.jpgIMG_20220108_2200493.jpg

    It is a Proxxon SD300, approximately a 5x12 mini lathe, and was made in the Republic of West Germany in 1982. Other than being very dirty and unused for years it seems to be in excellent shape. The bed looks pristine and most of the paint is perfectly intact, and with the locking screws backed out all four hand wheels move very smoothly.

    The biggest reason I sprang for this one is that it's entirely metric. My brain doesn't think in inches, and finding metric hobby lathes here in the US can be rather difficult. This is the only one I've seen in months of looking at local classifieds. It took about 9 hours of roundtrip driving in one day to get it from west Georgia and bring it home.

    It works, and came with most of the original accessories, but it is missing a few things. I don't have any of the original wrenches or screwdrivers or the manual, and it's missing the 50mm vise that it came with as part of a horizontal milling conversion kit. Fortunately I do have the angle plate for that and can probably find or convert a suitable tiny vise.
    The biggest hassle is that it's missing most of its power feed and threading change gears. Out of the original 11 it came with, these four were the only ones stuck to the machine, and they don't fit together in a way that turns the lead screw.

    IMG_20220110_1615574.jpg

    Original replacement gears are a pain to get hold of; I'd have to order used ones from England for something like $30 each (not gonna happen for plastic gears), try to see if the only importer of the modern clone of this machine has them in stock, buy off-the-shelf gears and modify them to fit, or I can try to get some 3D printed. The last is the most likely as I have a couple buddies who have 3D printers and these are fairly simple gears.

    I don't have any tooling other than the 1 HSS cutter it came with, and as anybody who owns a lathe knows that's the biggest cost hill to climb. Getting hold of working accessories for a lathe this old and small isn't the easiest, but there's a company in California that imports the modern Czech clones of this machine under the brand name Prazi. I'll have to order things like an independent four-jaw chuck from them and other things like a reasonably priced quick change tool post will have to come from England.

    The first step before I go buying a ton of other things though will be to completely take the machine apart and get it cleaned, oiled, and adjusted. I have a suspicion that the spindle bearings, which are grease-lubricated, haven't been repacked since they left the factory 40 years ago.

    After that, I have enough existing tooling to start making simple things like tubular spacers and bushings for the motorcycles. Maybe one day soon I'll be able to make some useful parts for other folks in the MOA that need them.
    Owner of the saddest 1997 R850R you ever did see.

  2. #2
    Back in the saddle again mikegalbicka's Avatar
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    Thanks for sharing. Takes me back to my early employment in tool and die shops and metal manufacturing in the 70's and 80's. We used to be able to make a lot of stuff we needed back then instead of buying it with those resources available. Saved a lot of money and got better products as a result. Good luck with your new hobby.

  3. #3
    It is likely best for you to not watch "This Old Tony" on YouTube. If you are watching (or yikes!, a subscriber), then it is too late and you will most likely be on the path to all sorts of projects and adding ever more tools.

    https://www.youtube.com/c/ThisOldTony

    Good Luck - Keep fingers out of moving equipment - and post pictures and details of projects - successes and failures! (Sometimes one can learn more from failures).

  4. #4
    Neglected Bike Adopter
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    Quote Originally Posted by robsryder View Post
    It is likely best for you to not watch "This Old Tony" on YouTube. If you are watching (or yikes!, a subscriber), then it is too late and you will most likely be on the path to all sorts of projects and adding ever more tools.

    https://www.youtube.com/c/ThisOldTony

    Good Luck - Keep fingers out of moving equipment - and post pictures and details of projects - successes and failures! (Sometimes one can learn more from failures).
    Oh it's way too late for that. I've been subscribed for years to his self-described "Great, one more stinkin' thing I'll need Channel." I'm pretty sure I've watched every single one of his videos multiple times, and I quote them to other people.

    Especially the rotary broach video, where he says "I've wanted one of these ever since I learned they exist." That thoroughly applies to me and a lot of metalworking tools.
    Owner of the saddest 1997 R850R you ever did see.

  5. #5
    bored, bored ... dlowry's Avatar
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    If you're going to 3D print the gears you're going to want much stronger than PLA. There are some nice carbon reinforced filaments. Run the gears for a bit with some old-fashioned toothpaste to smooth them out, clean them up, and they should be fine.
    Dave...
    ----------------
    15 R1200 RT, 12 G650GS
    83 Suzuki XN85 D Turbo

  6. #6
    Registered User Anyname's Avatar
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    Proxxon is still around. I don't know how their current lathe matches up with yours.

    The Little Machine Shop is a good source for tooling.
    BMW R bike rider, horizontally opposed to everything...

  7. #7
    Neglected Bike Adopter
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    Quote Originally Posted by dlowry View Post
    If you're going to 3D print the gears you're going to want much stronger than PLA. There are some nice carbon reinforced filaments. Run the gears for a bit with some old-fashioned toothpaste to smooth them out, clean them up, and they should be fine.
    From the brief research I did, nylon is what they'll be printed in. Though I'm only doing this to get a working set of power feed gears; for the real threading gears I think I'm either going to get new replacements from Prazi or buy off-the-shelf acetal gears in the correct tooth counts and adapt them.
    I'd try to adapt a set of steel Chinese mini-lathe gears, but I'm worried that the added inertia of steel gears might give the little 250W motor and the lead screw some trouble in the constant on-off work of thread cutting. This lathe has no half-nuts so threading operations have to be done by running the lathe forwards and backwards repeatedly. The typical mini-lathe gears also don't match all the tooth counts of this machine; a 100-tooth gear isn't in any of the sets I could see on Ebay.

    This is a pretty small lathe and the power feed rates on the threading chart are a fairly gentle 0.08mm/rev and 0.16mm/rev, plus I plan to keep my depth of cut minimal until I can figure out the limits.


    Unfortunately the modern Proxxon lathes have very little resemblance to mine other than the paint. There are one or two accessories they sell that might fit mine (a toolpost for cutting round features is one of them) but otherwise I have to go to Prazi as their SD300 is an identical machine in almost every way.

    I have done a bit of perusing on LittleMachineShop and will probably order from them at some point.
    Owner of the saddest 1997 R850R you ever did see.

  8. #8
    Registered User jandhumphreyme's Avatar
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    Congratulations. Its a long winding path your starting down. I had lathe and mill for many years but when we relocated for my work that equipment was all sold off, took me awhile after the move to figure out why I had spending money again. As for your threading gears, I would not worry about steel gears putting strain on the motor. You now need to source a mill and indexing head and cut your own gears.

    Good luck, looking forward to seeing some of your projects. BTW if your looking for a project, check out https://www.agelessengines.com/ one of those babies will keep you out of trouble for a time.
    So often times it happens that we live our lives in chains
    And we never even know we have the key

  9. #9
    Registered User barryg's Avatar
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    Basic Machining

    Basic machining is a good and rewarding hobby. Fun, frustrating, interesting and rewarding all at the same time. I was a machinist for over 20 years. I suggest U get a few basic machine shop training books to help explain the basic steps to operate the machinery. If U have a local vo-tech school; try to attend basic machine shop class. Its a good way to really jump start your machining ability.

  10. #10
    SURVIVOR akbeemer's Avatar
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    Once you get a bit of experience on your lathe you’ll notice you’re making many new friends.
    Kevin Huddy
    Silver City, Montana
    MOA# 24,790 Ambassador

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