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Setting up lathe for line boring?

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  • Setting up lathe for line boring?

    My smaller Jet 10x24 lathe has a t-slotted cross slide (my modification) which I thought would be useful for milling, but then I got a decent size mill. A few times I've wished I was set up for line boring and I think my larger Jet 12x48 lathe would be best suited for that. I have no experience line boring and have been considering whether I should slot this cross slide too or just drill and tap it for the attachment of holding jigs that I would make as needed. For general home/hobby use I guess t-slotting would be more flexible? Input welcome, thanks.

  • #2
    I guess it somewhat depends on what you're line boring. But given that the item being lined bored has to pass fully by the cutter on the shaft you'd have only around 12" available on the Jet and up to around 24" ability on the bigger machine. But then the lack of support on long overhung items would come into play. Consider that the lathe uses gravity primarily to hold the carriage secure to the bed. That and the cutting force being applied down through the "footprint" of the carriage to the bed. Shift that cutting force very far out past this footprint and things could get ugly in a hurry. So realistically I'd suggest that even your 12x48 machine would only be good for maybe 12 to 16" of length. Then there's the issue of support for the item being bored. If all the support is in the middle and provided by the cross slide there may be enough overhang to either side that it allows the force of the cutter to shift the part.

    Finally when I look at my own 12x36 lathe cross slide I don't see a whole lot of meat in the top of the cross slide that would permit me to cut significant T slots without fouling the dovetail under it or at the very least to significantly weaken the cross slide. And since most asian imported machines with a 12" throw tend to use the same carriages for the whole line of 24, 36 and 48" beds I can't help thinking that T slotting your cross slide would be a similarly poor idea.

    What I think I'd do if it were ever needed is drill and thread a sparse but reasonable pattern of holes for 3/8" threaded items. That would allow me to use my 3/8" clamping kit with the stock clamps or 3/8 hardware and custom fixturing. I'd then lightly countersink the threaded holes use fitted filler screws to plug the holes neatly flush when not required.
    Chilliwack BC, Canada

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    • #3
      What size and shape line boring lobs do you anticipate doing, and do you plan on keeping the 10x24? If the jobs aren't going to push the larger lathe with clearance issues, then I would go for the simpler method of taped holes and adapter plates as needed, and only slot the cross slide if necessary.

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      • #4
        Warning: Replying to older thread.

        I plan on trying something like this to line bore my air cooled vw cases:

        https://www.youtube.com/watch?v=IEOQFwjxw5Q

        I'll make a bushing for each end that fits where the oil seal normally would. I'm thinking I could make the bushings press fit size, then clamp the case around them.

        The boring bar is held between centers. Note that the weigh of the case is on the boring bar, and not the carriage. The only thing the carriage does is push the case along the boring bar.

        This may not work for your application, but I thought I'd pass it along. Best of luck.
        Definition: Racecar - a device that turns money into noise.

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