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  1. #1
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    Default Boring Between Centres ??

    Not the correct title. More like how do others go about setting up work to bore accurate holes at opposing ends of a workpiece on the same centreline?

    When I was making my toolholder I had to come up with an achievable alternative to the ground hole in the hardened toolholder of the original Multifix retractable threading tool. ( ground and hardened are assumptions because I can't imagine that they would be otherwise )

    Boring the block of 1045 from both ends and using bushes to support the ground and round shank of the formerly square Chinese threading tool seemed like it might work. Initially I thought I could bore the holes for the bushes on the mill. The block was marked out on a surface plate then clamped to an angle plate bolted to the mill's table. The idea was to end up with a hole around 22mm in diameter and about 18mm deep. I used a progression of drills then slot drills and then the inevitable slip out of alignment occurred due to the over optimistic p.ss poor clamping I thought I could get away with. This photo isn't of the boring but of the half hearted clamping -

    DSC_8708 (Large).jpg

    I was using a 19mm slot drill when the block moved. Fortunately the damage was minimal but the block had moved out of alignment. A more rigid setup was the universal vice but the cost of that rigidity was the inability to be able to bore the opposite end of the block because there was not enough room to install the cutter above the work. What I did do was centre drill the bottom of the bored hole and the unborable end of the block.

    DSC_8720 (Large).jpg

    With those two centre holes I was able to mount the block between centres on the lathe and use a vice for support facilitating the milling, boring and through drilling of the block. When I did bore out the hole that I couldn't bore on the mill, I centre drilled the bottom of the hole to allow the rotation and reclamping of the block while maintaining alignment before the through drilling. After the though drilling I used the cast iron bushes and the cut down Chinese threading tool installed in the block for alignment. I had previously centre drilled the Chinese tool because that required turning and grinding between centres.

    DSC_8748 (Large).jpg DSC_8746 (Large).jpg DSC_8750 (Large).jpg DSC_8743 (Large).jpg

    Being able to remove and reposition the block between centres was handy. What proved even handier when it came to modifying the Chinese threading tool was having another 9" Hercus. I was able to swap saddles, the workpiece could remain insitu and in alignment while perched on a milk crate on the floor. The Chinese tool required an extension involving some drilling and boring along with facing on the mill. All easily achieved because the block, unmoved in the vice, maintained accurate alignment.


    IMG_20180206_143344300 (Large).jpg IMG_20180207_094212835 (1) (Large).jpg


    Now all this was pretty easy because my block was solid and I had the luxury of being able to drill a couple of centre holes. Line boring might have been an option but would have required the making of a reversible boring bar. I managed to get away with it by using a boring head.

    Any suggestions for an alternative method?

    Bob.

  2. #2
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    Default

    Could you have tilted the mill head and had the vice in the normal orientation, kind of like a tiny HBM? I forget if the scaublin vertical head has tilt.

  3. #3
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    Default

    Quote Originally Posted by caskwarrior View Post
    Could you have tilted the mill head and had the vice in the normal orientation, kind of like a tiny HBM? I forget if the scaublin vertical head has tilt.
    Cask,

    The 13's head does rotate but the there would have been no supporting tailstock which proved essential in the setup I used. The mill is small, its table is 600mm long and while the entire table assembly can be slid along the vertical of the face of the X slide, there would not be sufficient space to accommodate the boring head with its extended boring bar and the workpiece. The green lathe on the other hand has a long bed, long enough for two saddles, a tailstock and room to spare.


    DSC_8926 (Large).jpg

    Bob.

  4. #4
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    Default

    Hi Bob, l guess that we all think and do things differently, I suppose this has a lot to do with tools and machines on hand.
    I have a lathe a bit larger than the hercus so I would have put that in the 4 jaw and bored it straight through, bored the outer end for the bush then put a chamfer on the back of the hole before removing and then spun it around to bore for the other bush.
    I would find the centre of the bore in a similar manner to this https://www.youtube.com/watch?v=ptmxSjxWM70

    However in the past i have cut square material longer and turned a surface for the use of the fixed steady and turned or cut that off after, you may have been able to have done the milling after the boring.
    cheers, shed

  5. #5
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    Bob I face an almost existential crisis everytime I see you making all this lovely time consuming stuff in an environment that is not only clean but actually spotless. Here I am turning out garbage in a filthy unpainted poorly wired favella.

  6. #6
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    Quote Originally Posted by shedhappens View Post
    Hi Bob, l guess that we all think and do things differently, I suppose this has a lot to do with tools and machines on hand.
    I have a lathe a bit larger than the hercus so I would have put that in the 4 jaw and bored it straight through, bored the outer end for the bush then put a chamfer on the back of the hole before removing and then spun it around to bore for the other bush.
    I would find the centre of the bore in a similar manner to this https://www.youtube.com/watch?v=ptmxSjxWM70

    However in the past i have cut square material longer and turned a surface for the use of the fixed steady and turned or cut that off after, you may have been able to have done the milling after the boring.
    cheers, shed
    That is a neat trick Shed. There was an image of a similar setup on the cover of an old Workshop Practise Series book I bought about 15 years ago. I have used the trick a number of times.

    I had thought of mounting the block on an angle fixed to the lathe's faceplate but abandoned the idea because I reckoned the between centres thing had more promise and possibly less chance of disaster.

    There are times when a beefier lathe and a less dwarfish mill would be great but you end up tailoring the stuff you do to suit the gear you have.

    Bob.

  7. #7
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    Quote Originally Posted by caskwarrior View Post
    Bob I face an almost existential crisis everytime I see you making all this lovely time consuming stuff in an environment that is not only clean but actually spotless. Here I am turning out garbage in a filthy unpainted poorly wired favella.
    I yearn for a favela Cask. My shed is a midden. I use the camera carefully.

    Bob.

  8. #8
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    Default

    What if you removed the universal table and fixed a vice or another method of work holding directly onto the 2 T-slots on the front face of the mill?

  9. #9
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    Default

    Bob,you have answered a couple of questions that I was going to ask in the original thread regarding boring the hole and the length of the Chinese toolholder. The Multifix design does not appear to have bushes, why did you decide to use them? The bore in the bushes appear to be honed, is that how they were finished or is that just the finish from emery cloth?

    Lex.

  10. #10
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    Lex,

    It was a decision based on an assumption that the reasonably hard Chinese toolholder would probably slide better in easily replaceable cast iron bushes than a bored bore in the 1045 block. Keep in mind that I had no great faith that all this would work, my only guide was a not great quality YouTube clip showing a brief view of the dismantled Multifix.

    The bushes are not honed, only carefully bored. They were tight when first fitted to the ground 16mm shaft of the toolholder and they have subsequently loosened a touch after fitting and fiddling. The idea of the split body was that they might be able to be clamped tighter. I imagine that's why the Multifix body is split ( strangely it is not split on all of the examples I've looked at ). The screw on Burnerd chuck that fits the 13's dividing head is secured with a clamping ring hence the optimism that my split body might do the same.

    I ground the bar before making the bushes. Last night I looked at buying a cheap Chinese 16mm reamer thinking a new pair of bushes could be reamed prior to making another bar for the small Ifanger threading tool. Thinking about it, I'm not sure how I would go removing and replacing the bar between centres on the T and C grinder to check the fit. I could end up turning ( or grinding! ) good 4140 into scrap.

    Bob.


    DSC_8509 a (Large).jpg DSC_8762 (Large).jpg DSC_8772 (Large).jpg

  11. #11
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    Default

    Nice work Bob.

    Lots of ways to skin that cat and you did well. Line boring would be the ultimate for accuracy. I'll throw another out there for what it's worth.

    Chuck in a 4 jaw (faceplate if it's large) and through bore. Chuck some scrap and turn it down so it's a slip fit for the bore to form a spigot. Super glue the part to the spigot. Bore the bushing. Use heat to release the super glue, reverse and repeat. Super glue makes a good temporary bond and is less fiddly than shrinking something on, though the latter is arguably even more accurate. If you were doing a lot of these parts you'd probably make an expanding spigot. A lot depends on just what accuracy you need.

  12. #12
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    Default

    Easy to speculate in hindsight, but I think I would have drilled a hole through the block (under final bored size) and then mounted it up on the toolpost and used the height adjustment screw and cross feed to position the hole on axis. Then use either a between centres boring bar or a boring head on the lathe as you have to bore the hole/ counter bore.

    In the past on the mill I've used two angle plates (nominally at 90 degrees) or a large V block on it's side provide a positive location for something like that to locate against. One of the things I've learnt over the years is to plan for undesirable events, so if something may slip I try to have a way of repositioning, whether that be a sacrificial boss/ surface or a solid as all get out fixture (firmly attached angle plates for example) that lets me re-establish position with my pp clamping if needed.

    Given that you can determine the offset of the hole from opposing surfaces, a couple of angle plates may have been my preferred 'mill only' method

    Michael

  13. #13
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    Default

    Quote Originally Posted by devarda View Post
    What if you removed the universal table and fixed a vice or another method of work holding directly onto the 2 T-slots on the front face of the mill?
    Welcome to the Forum Aaron.

    Something weird is going on because notification of your post arrived in my gmail inbox only yesterday.

    The problem I had was the two counterbores and their alignment. A swivelling vice mounted to the vertical face of the slide would still require movement of the slide in the X axis to realign the bore when the vice is rotated 180 degrees. Too many opportunities for non alignment and my between centres setup in the lathe worked out well enough.

    Often I have pondered removing the table to provide access to a whole lot more Z. The prospect of retramming the table on its three axes has made me seek other alternatives. It is handy though that we do have that option -

    027 (Large) (2).JPG

    Bob.

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