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Lathe tailstock casting repair?

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  • Lathe tailstock casting repair?

    I had trouble with a taper appearing when I engaged the tailstock on a long, thin (180mm stick-out of 10mm alu) rod and took a light cut to get the dimensions.
    I broke out a test bar between centres and adjusted it with a DTI and then left it overnight. Checked it the next day and it was way out and wouldn't adjust in one direction. Took it apart and it seems I've broken the pillar off the base casting that one of the pair of set screws bear against:





    If I lived in the US, I could order a replacement casting from stock for just over 20 buck. I think I can get it here (UK) from ArcEuroTrade but it'll be special order from Sieg, cost me twice that and take about two months to arrive.

    I tried using one set screw to align it and the tiny ones that I'm assuming adjust angle (you can see the dimples they create in the second photo on the only machined upright surfaces) as locks and the bar turned fine - looked fine, sounded fine - but when I stopped the lathe, the finish looked like I'd beaten it to dimension with a hammer.

    I was thinking I could JB Weld it back together but don't know how strong/rigid/reliable that would be. Do you reckon I could drill down the centre of both pieces (in one, with the pieces assembled for concentricity) and then pin it with a 4mm or 6mm dowel and then JB weld the fracture as well? Or is there a better way? The part that's broken off is about 11.5mm x 14 x 20 and tapers down to about 7.5mm so the 6mm dowel may be too big. I also have Loctite 638 that could be applied to the dowel for belt and braces

    If this is a good way of doing it, should I be drilling to 3.9mm for a 4mm dowel which will probably give me a 3.95mm hole for a press-fit or should I be reaming it to 4mm and letting the Loctite take up any slack? Not massively familiar with cast iron....or press-fits, for that matter.

    Thanks guys, appreciate the advise.

    Gareth



  • #2
    Brazing job.

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    • #3
      I have been looking for an excuse to buy a blow torch for a while - to play around with hardening etc. Given a total inexperience with brazing (electrical soldering yes, but nothing bigger) do you reckon that's the best way?

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      • #4
        That's a rather gruesome looking casting. I would cut the other one off (before it also breaks) and file the bases flat then bolt a square block of steel down to the base for the screws to jack against.
        Peter - novice home machinist, modern motorcycle enthusiast.

        Denford Viceroy 280 Synchro (11 x 24)
        Herbert 0V adapted to R8 by 'Sir John'.
        Monarch 10EE 1942

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        • #5
          Broke off the other too and mill flat pocket there. Insert piece of mysterium steel and lock it in place with 2 bolts and drop of loctite.
          Location: Helsinki, Finland, Europe

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          • #6
            Originally posted by Peter. View Post
            That's a rather gruesome looking casting.
            Well, she's certainly no lovingly hand-finished old iron....you get what you pay for these days and that means they only bother to make a passing attempt at finishing the parts you'll see.

            Well, that's two ideas I'd certainly not thought of. Might have to order some suitable mysterium as it seems a shame to inefficiently take it out of a chunk of 70mm round bar which is the only thing I have in steel that large enough.
            If I go that route I think I'll have to stock up as it's about £9 (GBP) for 30x20x100mm or £21 for 30x20x1000mm. Assume that postage is the issue but it's linear up to 500mm and then just a few quid more to double it.

            Brazing would definitely be quicker if I already had the stuff - I'm still kind of tempted, it would still be quicker if ordered off Amazon and could still resort to option two...but more than three times the cost.
            Last edited by Cenedd; 09-04-2020, 03:10 PM.

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            • #7
              Looks like the crappiest of Chinesium. Might be a good time to upgrade.
              12" x 35" Logan 2557V lathe
              Index "Super 55" mill
              18" Vectrax vertical bandsaw
              7" x 10" Vectrax mitering bandsaw
              24" State disc sander

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              • #8
                A perfect brazing opportunity

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                • #9
                  Originally posted by ezduzit View Post
                  Looks like the crappiest of Chinesium. Might be a good time to upgrade.
                  I'd be the first to agree as I've bought my fair share of it - some bad, some adequate and some sold by Starrett. These days you get it everywhere. I fear though that this could be user-error. I'm sure there's a machining equivalent of Problem Exists Between Chair And Keyboard. There are two opposed set screws for alignment. These are what I'd been tightening and loosening....but there are also two tiny set screws at the back of the casting (away from the head) and I'd figured they were for angular alignment and not touched them. Trouble is that if they were tight, they'd be making adjustment left/right much harder and hence more force....so it could be that I set it up to crack. I'll agree the casting is bad and it's certainly better (more reinforced) one side than the other.....but that doesn't mean I didn't screw up. It's a learning opportunity at the end of the day I guess - both in avoiding it and fixing it.
                  The only really irritating thing is that I was in the middle of a project with my son. I can (and have) ordered bar stock that's already to size but the post is ....well, you roll the dice. Things should be finished for presentation on Monday night but I suspect that stock won't turn up until Monday at the earliest

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                  • #10
                    Originally posted by DrMike View Post
                    A perfect brazing opportunity
                    Yep, learn to braze and fix your problem yourself. While you are at it braze a bridge between the two pillars so the low quality casting won’t break in a second location.

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                    • #11
                      Just use a longer screw so they both push on the remaining pillar.
                      Simple.

                      -D
                      DZER

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                      • #12
                        Originally posted by Doozer View Post
                        Just use a longer screw so they both push on the remaining pillar.
                        Simple.

                        -D
                        You could do that, no issue. Since the screw may be hard to get with long threaded part (carriage bolts are commonly long threads, and have built-in wrench flats), you could make one, but you might need to have the T/S to do it.
                        1601

                        Keep eye on ball.
                        Hashim Khan

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                        • #13
                          Yep, quick & simple brazing job.

                          Dan
                          Salem, Oregon

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                          • #14
                            To quote the late John Stevenson 'Clumsy b-----d'!
                            'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                            • #15
                              Originally posted by Doozer View Post
                              Just use a longer screw so they both push on the remaining pillar.
                              Simple.

                              -D
                              Doozer hits the nail on the head once again. Simple, easy fix. Kicking myself for not thinking of that on my own.

                              Originally posted by J Tiers View Post

                              You could do that, no issue. Since the screw may be hard to get with long threaded part (carriage bolts are commonly long threads, and have built-in wrench flats), you could make one, but you might need to have the T/S to do it.
                              McMaster sells long set screws. Might have to buy 25 of them, but that's easier than a braze job. Surely the UK has a similar distributor.
                              21" Royersford Excelsior CamelBack Drillpress Restoration
                              1943 Sidney 16x54 Lathe Restoration

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