4 jaw lathe chuck recommendations?

Discussion in 'Foundry tools and flasks' started by Zapins, Oct 8, 2017.

  1. Zapins

    Zapins Gold

    Bit of a problem. The chuck I got does not fit the threads on the lathe. The chuck female diameter is too big. I need an adapter or backplate to fit.

    I couldn't find the measurements of the lathe threads. Any idea how to go about this?
     
  2. crazybillybob

    crazybillybob Silver Banner Member

    Zap,
    What is the make and model of the lathe? That will help us narrow it down. Then a quick measurement will get you there. Ie old South bends had 2 sizes 2 1/4" or 1 7/8" so even a rough measurement with a scale or tape would tell you the one you need.
    Some lathes use tapered threads...so beware of that too.

    CBB
     
  3. Mister ED

    Mister ED Silver

    Most threaded spindles are 1 1/2 - 8, 1 3/4 - 8, 2 1/4 - 8, or 2 3/8 - 6. Most common (that I am aware of) are 1 1/2 - 8 and 2 1/4 -8. I thought the smaller SB lathes were 1 1/2 and the larger 2 1/4.

    Like CrazyBillBob said, take some measurements. Also throw a thread gauge on on the new chuck, that will help reducing the selection on the larger end. Also, does this chuck have a backing plate or are the threads integral?

    -------------------------------
    I'll be darned, SB did have a 1 7/8 - 8 as well.
     
    Last edited: Sep 12, 2018
  4. I think he said it was a SB 13" so if you're right he has a 2-1/4" and needs to adapt to 1-7/8".
     
  5. Mister ED

    Mister ED Silver

    oldironfarmer likes this.
  6. Looks like they used from 1-1/2" to 2-5/8". He's going to have to measure his chuck to make sure which bore he has before making an adapter.
     
  7. crazybillybob

    crazybillybob Silver Banner Member

    The pre WWII sb heavy 10,11,and 13 used the same spindle. Pretty much built the same just a different size riser block. That's why I said my SB takes a 1 7/8 x8 backing plate.
    Depending on how the backing plate mounts to your Chuck. You might be able to get a used plate on eBay https://m.ebay.com/itm/lathe-backin...758723?hash=item2cd62bd883:g:OVoAAOSwi49bJx7s
    And machine it to fit your new Chuck.
    Or you will have to get a chunk of cast iron and machine your own backing plate. Here's a This Old Tony YouTube video on how to do that.... he's better at explaining it than I am.
     
  8. Mister ED

    Mister ED Silver

    So crazybillybob, sounds like the 1 7/8 is no longer available anywhere?

    For the "chunk of cast iron", I think Zapins could take a 1 1/2 backing plate and punch it out & thread it. I will see if I have one laying around from my old lathe. New one is 2 1/4.
     
  9. Zapins

    Zapins Gold

    Ugh. This looks like something well beyond what I know how to do. I have a feeling if I take it to a machine shop they'll charge me more than I paid for the chuck to make a proper backing plate for it. I had wanted to use the 4 jaw to learn how to use the lathe. I bet all you lathe junkies are palming your foreheads thinking how easy a project this is! This is what happens when school budget cuts take out metal shop class from HS. This is what the back of the 4 jaw looks like. VideoCapture_20180913-181154.jpg VideoCapture_20180913-181137.jpg

    I think 1 7/8" sounds correct. The back plate is just slightly too large to fit on the spindle. So I'm guessing it is 1 7/8." Unfortunately I didn't have my micrometer with me when I was last home so I didn't measure it. And I didn't think of using a tape measure at the time (d'oh). Also there are no markings on the lathe or 3 jaw chuck that tell the size and thread count.
     
  10. Robert

    Robert Silver

    It is traditional to machine the backing plate to fit the chuck. This way, the plate is perfectly true to the spindle. The process is not at all difficult and is kind of fun and satisfying when it goes well. It may be necessary to have a means to drill the bolt hole circle if this is not already done. That is easiest with a rotary table but there are other methods. I usually machine my back plate about .002 over the diameter of the chuck and then heat the chuck in the oven to get a nice tight fit.

    https://www.hobby-machinist.com/threads/bolt-holes-for-chuck-adaptor-plate.41939/

    Robert (RWM)
     
  11. dtsh

    dtsh Silver

    It's really not that hard, though I recommend practicing the broing and threadcutting operations on something other than the backplate as learning usually involves some error. I wouldn't take it to someone else, it will need to be fitted to the machine it's intended for.
    At minimum, you'll need a micrometer to measure the spindle, a telescoping gauge for the bore in the plate, and a thread pitch gauge. I'm no machinist, but this is something I've sucessfully done (on my second try) and I don't think I'm any more capable than you are.
     
  12. You said you wanted to use the four jaw to learn how to use the lathe. Does your three jaw not work? I may have missed something.

    If you are trying to learn to dial in a 4 jaw, you can chuck the four jaw in the three jaw and use it that way. I've got a buddy who leaves his 4 jaw on the lathe and chucks a three jaw in it for 3 jaw work. He is an excellent experienced machinist.

    This is a good time to learn to thread. Get a heavy piece of pipe or cast yourself one out of brass and thread the ID to 1-7/8"-8 and the O.D. to 2-1/4"-8, leaving a flange on the O.D. to seat the 4 jaw into. Not ideal but it works.
     
  13. Petee716

    Petee716 Gold Banner Member

    Among other things that need attention on my Seneca Falls lathe is the 3jaw seized on the spindle. The piggyback solution OIF describes may be how I'll run my 4jaw if I can't free it up.
    You can buy a backing plate blank already threaded from Shars or EBay for less than $100 and you would just have to do some boring and facing and then drill and tap your holes. You can practice those techniques on something else till you feel confident enough and then screw the blank onto your spindle and have at it. I'm not sure how I found this link, maybe here, but it has some good details about fitting:
    http://www.lathes.co.uk/latheparts/page7.html

    Pete
     
  14. crazybillybob

    crazybillybob Silver Banner Member

    Yes you could punch out a 1-1/2" backing plate to 1-7/8" if there's enough meat on her.

    Zap, You're going to want to trim the outside and shoulder register down on any backing plate blank you get. This makes it true to your machine (dtsh mentioned this already). If the boring and threading is what's hanging you up you can pick up a backing plate off ebay and just true it up and drill to fit your chuck. 1-7/8"x8 is an odd size, it was used by very few lathes and only a long time ago. There was a few companies that sold backingplate blanks a on time not too long ago but I think the last one went belly up 2-3 years ago. You can try to reach out t grizzly they own the Southbend company (name) now and had a very good parts selection the last time I called them. I feel like they had backingplate blanks but they wanted top $$ for them. I'd offer to make one up for you... but my lathe's still in pieces and I honestly don't know when it will be back in running order (it's been down for 8 years...to give you the time scale I've been working with).

    I feel you on the closing of the metal shops in schools. I missed out in HS but was lucky enough to go to a Engineering collage that had some vintage WWII surplus lathes in the machine shop, and using them was a required class. (we also had a robotic manufacturing cell we played with later).

    CBB
     
  15. Zapins

    Zapins Gold

    It does, but I can't take a part out flip it around or do something to it, then put it back without it being horribly out of center. I also can't cut holes or lathe strangely shaped objects which I'd like to be able to do.

    This is genius. Maybe I'll do that. I think I can just clamp the 4 jaw into the 3 jaw. But will it be horribly out of center too? Guess it doesn't matter that much since its a 4 jaw adjustable! Though it is heavy at like 80 or 90 lbs so I hope it doesn't slip.

    Yeah you and the other guys are probably right. I'm just a bit timid about trying threading. I need to get myself some practice stock/scrap and just try everything.

    I'm missing the threading dial, so I 3D printed myself one at 100% infill. Seems like it came out pretty well. I just need to install it, that will let me stop and start a cut.

    Also, part of my concern is how to grind the cutting bits correctly. I need to practice that. Probably not bad once you know what you're doing but when its your first time and there isn't anyone to lead you through it in person and you've got 20 other projects to do (castings) the hours of frustration and failure that inevitably await at the side of the lathe somehow keep getting put to the bottom of the to do pile during my short 1 month breaks back at home.

    This might be what I'll have to do. I could probably buy one and muddle through simple facing and edge trimming but boring and threading an internal thread of the right size and shape is daunting.

    At worst a back plate with hole already made could be given to a machinist for facing / finishing for a lot cheaper than totally fabricating it from scratch.

    Is there anything I need to look for when buying a 1-7/8" premade back plate so it can be machined and fit to mine?

    Yeah I hate it. My dad got to learn on lathes and mills and made a few very nice tools which he still has today and gave to me. In college they had no shop course. There was a shop with a few power tools in the engineering department for use making robotic parts but even to use their drill press they wanted me to go through an entire course in safety around machines. So I said I'll figure it out on my own in my own shop. I'll bleed when I want to bleed on whatever machine I want to bleed on thank you very much.
     
  16. Zapins

    Zapins Gold

    Thanks, I think I can get there eventually. Problem is I'm not around my lathe/big tools for more than a month or two a year so it is hard to tinker and figure things out slowly. I do my learning in short intense spurts when I'm home and I usually have too many other projects I rush to get done in order to blow 3 weeks on practicing and figuring out mistakes, buying new materials and getting it working. I hate how it is but that's what I've got to work with at the moment.
     
  17. Zapins

    Zapins Gold

  18. A few comments. How bad is your three jaw chuck. 0.004" mismatch? If it's a lot more, like a 1/4", maybe the jaws aren't in their correct position. They only go in one slot to work right, and should meet nicely in the center. If they don't meet in the center they may be in the wrong slots. You would take them all out and look at the scroll threads on each jaw. Put the one with the tooth farthest down in first, and work from there.

    You can buy premade carbide threading bits, but they're easy to grind. Buy yourself an angle guide. They can be pretty costly. https://www.ebay.com/itm/Screw-Thre...563081&hash=item25e9e69fe3:g:AlAAAOSwXtNaT0kX

    One trick to successful threading is to set your compound at half the thread angle (30 degrees for a 60 degree thread) and when you advance the tool you use the compound to the tool is only cutting on one side, advance it parallel to the other side.

    I haven't seen any pictures of your 4 jaw. Does it have a back plate? I guess you could use a face plate like you show but that's not a back plate. You want to face it on your lathe to compensate for your spindle being crooked. When you screw the backing plate onto the spindle and face it you have removed one source of error. If you have a machinist face it you introduce his error on top of yours.
     
  19. Robert

    Robert Silver

    That's what you need as long as the OD is big enough to fit the recess in the back of your chuck. Also the threads on that one look a little f''ed up. That is a great price so far and looks like it will fit. Too bad its not a buy it now. The threads are rough but would probably hold just fine. I would grab it. If you are keeping the lathe you will definitely use it.
    Do you have a way to drill the bolt hole circle? How many holes is it?
    R
     
    Last edited: Sep 15, 2018
  20. crazybillybob

    crazybillybob Silver Banner Member

    That ebay backing plate has a few issues.... but It's better than what you got now. If you can score it for $30 it's a start. You could pick it up make it fit your 4 jaw and if you don't like it use it on the 4 jaw to make a new one! Sometimes you learn more from using a crap tool to make a good tool :) You can make that bolt circle with a drill press (Pillar drill) a divider, and a set of calipers. While it's on the lathe for machining the register and OD make a light circle where the bolt circle of the chuck is. Then set you dividers to the correct distance between the holes and walk the around the scribed circle. Might take a try or two to get them just so but the divider should start and end at the exact same spot. Center punch the spots, drill to proper clearance size for the mounting screws. You can counter bore the back for extra style points.
    CBB
     
    Robert likes this.

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