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  1. #1
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default Line boring, and a PTO for the lathe.

    I posted a question about line-boring setups a few months ago, seeking inspiration for how I was going to go about boring the frame for my tractor front-end-loader. I put a few ideas from other people together, plus a little of my own brainstorming, and got the job done. This might be of use to others attacking this procedure in the future.

    I made a shaft with a splined end to replicate the PTO output on a tractor.
    pto spline milling 1.jpgpto drive shaft finished.jpg

    The shaft was held in the lathe chuck, with the splined end protruding out of the back end of the spindle bore, with a simple tapered collar keeping the back end concentric.
    lathe PTO output.jpg

    I made up a socket to slide over the end of a length of 25mm shaft; the socket is keyed to the shaft and splined on the other end, same PTO splines as the lathe output shaft.
    PTO 25mm socket.jpg

    These two splined shafts enable the 25mm boring shaft to be driven from the rear of the lathe via a telescopic PTO drive shaft from a tractor implement, in this case my slasher. For those unfamiliar, a tractor PTO shaft is like an automotive prop shaft, with a uni joint at each end and a sliding section between. The sliding section enables the shaft to extend / retract to accommodate the feed of the boring operation.

    PTO output connected.jpg

    I used a steel-topped welding bench to set up the boring job, the business end of the loader frame was plonked up on the steel bench and tacked in place with scrap metal legs. I used flange-mount self-aligning bearings to carry the boring shaft, everything welded to the steel bench to provide a stable setup with the correct relationship between the boring shaft and the work, aligned behind the lathe so that drive and feed could be taken from the lathe.
    boring shaft mounted 1.jpgPTO driveshaft connected.jpg

    The next bit was the fun part- taking feed from the lathe as well as rotational drive.
    The boring shaft is free to slide through the four flange-mount bearings that keep it aligned in the bore. A fifth bearing- this time in a pillow-block housing- was fixed to the shaft with grub screws to keep it in place longitudinally. this was attached to a jury-rigged arrangement that connects back to the lathe toolpost, so that feed can be applied to the boring shaft from the lathe.
    boring shaft feed setup.jpgline boring shaft and feed setup.jpgline boring feed toolpost.jpg

    The boring was done with a HSS cutter mounted in a cross-hole hole in the boring shaft, using vernier calipers to extend the cutter the required amount between passes.

    The setup worked a treat, although I had to add some bracing to the frame of my welding bench to make it rigid enough for the purpose. Had to add some extra bracing to the boring shaft carrier bearings and loader arm ends as well before it was all rigid enough to cope with the interrupted cut I was getting until the bores neared alignment.

    Facing the ends of the bores was problematic. The 'proper' line-boring units have a facing gadget that feeds the tool across the face but I had to find another way. I started by using the surface grinder to make a tool with a long, straight cutting edge to sweep the face.
    facing tool mounted.jpg
    and promptly snapped it off in the first cut.
    facing tool broken.jpg
    The second attempt went better, essentially a shorter version of the same tool, starting with a smaller diameter sweep and extending it out in around .150" increments, blending the surface of each subsequent pass. The outer part of the barrels has been hardened by the process of welding them in place, the HSS cutter would not cut beyond a certain point so they will need to be ground off but there is enough surface with a face square to each bore.
    first barrel faced.jpg

  2. #2
    Join Date
    Aug 2019
    Location
    Revesby - Sydney Australia
    Age
    56
    Posts
    1,183

    Default

    Impressive Frankenstein-ing of a line borer!

    For the facing, a die grinder clamped to the shaft?

  3. #3
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    Quote Originally Posted by nigelpearson View Post
    Impressive Frankenstein-ing of a line borer!

    For the facing, a die grinder clamped to the shaft?
    That would be interesting to try. I plan to chamfer the outer rim with an angle grinder and flap wheel, leaving the faced area proud.

  4. #4
    Join Date
    Sep 2010
    Location
    Port Sorell, Tasmania
    Posts
    74

    Default

    That's an impressive example of improvisation Pete

  5. #5
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    Thinking out of the box
    Good one mate,

    Grahame

  6. #6
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    I made a puller to insert the bushes into the bores that were line-bored above. The bushes were made with an interference fit of .0025" so it was always going to be a challenge to get them into the bores. The puller consists of a 12" length of unknownium bar with a 1" 20tpi UNEF thread, and a nut made from an offcut of 4140 with a full 2" of thread. Both threads cut with single-point HSS tooling in the lathe. Milled two flats on the nut to get a big shifter on and drilled a 5/8 hole through the end of the threaded rod to put a bar through.
    bush puller 1.jpg
    The bushes have been in the freezer for several days while I got things organised, then the barrel started out nice and warm from grinding the outer part of the faces back. I introduced the cold bush to the warm bore and started turning the puller. Got to the point where I could not turn it any more, obviously by this time both parts are at the same temperature a the bush is only half-way in.
    bush half pulled.jpg
    The thing would still move if I could turn the screw, but it had got so difficult to turn that it was defeating me. I had expected my threads to strip before it got to this stage. I was brainstorming ways of applying more torque to the screw than I was able to apply by hand with the bar I had. Came up with the ridiculous idea of attaching something to the wheel of the tractor to apply the rotation required- I considered using the PTO but that turns too fast and I also didn't want to risk damaging the internals. Considering that the tractor in Low 1st goes slower than walking pace and the wheels are about 5' diameter, i guess the axle turns pretty slow. Why not give it a shot.
    I cobbled together an adaptor to attach to the wheel, with a sliding offcut of triangular PTO shaft welded in the centre and slotted at the outer end to drive the screw.
    tractor wheel adaptor.jpg

    Lined the tractor up alongside the business end of the loader frame and jacked up the rear end of the tractor, then slid the outer of the shaft over the screw.
    tractor driving puller.jpg
    Both rear wheels off the floor and diff lock engaged to get the slowest possible drive.
    I was expecting the threads to strip straight away, but they held. The bush came in ever-so-slowly. The cast-iron gear I was using as a spacer (first thing I picked up with the right size bore) shattered at one stage and I thought the threads had let go after all. I replaced the gear with something else that came to hand with the right size hole and continued. Things shuddered and complained a lot as it got close, then pretty much stopped with the bush about .020" short of home. I think I'll call it good. I used reverse gear to back the puller off but all that achieved was busting the end of the drive shaft. Will need some modification before attacking the rest of the bushes but i'll consider the concept proven.
    bush inserted.jpgbush just proud.jpgbush just shy.jpg


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    Last edited by Pete O; 7th Apr 2020 at 07:16 PM. Reason: re=load pictures

  7. #7
    Join Date
    Nov 2011
    Location
    Port Sephens NSW Southside
    Posts
    123

    Default

    No pics showing.
    "Invalid Attachment specified. If you followed a valid link, please notify the administrator"

    JohnQ

  8. #8
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    Quote Originally Posted by JohnQ View Post
    No pics showing.
    "Invalid Attachment specified. If you followed a valid link, please notify the administrator"

    JohnQ
    Hmm, they show for me- I'll have a fiddle and see what I can do.

  9. #9
    Join Date
    Apr 2018
    Location
    Drouin Vic
    Posts
    633

    Default

    Re-loaded the pics, someone please let me know if they are showing now.

  10. #10
    Join Date
    Sep 2008
    Location
    Riddells Creek, Vic.
    Posts
    831

    Default

    Yes, I can see 7 photos Pete. Good job by the way.

  11. #11
    Join Date
    Nov 2011
    Location
    Port Sephens NSW Southside
    Posts
    123

    Default

    All good tks

  12. #12
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

    Default

    Hi Pete,

    I wonder if some oil would have helped ! Though now its cooled off heating the outer whilst applying pressure to the bush would see it home.

    Either way nice improvisation.
    Best Regards:
    Baron J.

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