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  1. #226
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    Dec 2007
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    Adelaide
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    On my spindle the shaft can float back and forward, the preload springs keep tension on it pulling the spindle back towards the pulley end, the radial groove in each of the end caps is part of the dust seal.
    There is a good discussion on home workshop built grinding spindles here

    https://www.practicalmachinist.com/v...arings-144760/

  2. #227
    Join Date
    Nov 2017
    Location
    Geelong, Australia
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    57
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    Definitely some good info in that PM discussion - thanks Familyguy.

    Particularly from post #13 "If you use spring preloads mount the front bearing rigid and make sure the spring pulls the spindle towards the back (you don't want to unload the preload when face wheel grinding). "

    That would be a gotcha for inexperienced players...

    Steve

  3. #228
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    Dec 2007
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    Adelaide
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    I need to correct myself the grooves I mentioned are I think axial not radial ie aligned with the axis, I had some trouble machining them and eventually made a cutter that looked similar to a hole saw, it worked a treat
    Attached Images Attached Images

  4. #229
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    6,439

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    Hi Familyguy, Steve, guys,

    Thanks for your thoughts.

    Quote Originally Posted by familyguy View Post
    I need to correct myself the grooves I mentioned are I think axial not radial ie aligned with the axis, I had some trouble machining them and eventually made a cutter that looked similar to a hole saw, it worked a treat
    That duplicate post confused me for a moment ! Yes I see what you mean. The securing nut would have to be much deeper to accommodate a face groove. That would also mean that the bearing pack would have to be slightly further back inside the housing.

    An oiled felt washer would sort out any dust that might enter there, and provide some lubrication into the gap between the nut and shaft surfaces. I'll have to give that some more thought because I was thinking about some pin holes for a pin spanner in the face of that part.

    Actually that raises a question about lubrication, since the bearings I want to use are shielded and not sealed, would the ability to add lubrication between the two bearings be an advantage. I was thinking something like a ball oiler in the housing.
    Best Regards:
    Baron J.

  5. #230
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Thumbs up Simple Grinding Spindle, -3

    Hi Guys,

    Another drawing showing the arrangement of the bearings and a Belleville spring washer. The end cap is not shown on this drawing. However I've shown the internal shoulder which the rear bearing outer rests against, the internal spacer between the bearing inners and the pre-load Belleville washer in red.

    Spindle Design 3.png

    The bearings are shown in yellow and the internal spacer in black. I've also added a ball oiler to allow for lubrication of the bearings.

    There are no dimensions simply because I haven't actually got the bearings or the correct Belleville spring washer yet. Also I haven't decided how I'm going to mount the actual grinding wheel onto the spindle shaft.

    Thanks Guys
    Best Regards:
    Baron J.

  6. #231
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    Dec 2007
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    Adelaide
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    The end caps on my spindle are tightened with a C spanner.

  7. #232
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    Sep 2012
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    York, North Yorkshire UK
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    Thumbs up Simple Grinding Spindle, -2b

    Hi Familyguy, Guys,

    I've redone the drawing (2a) now called (2b) showing your suggested castelations for a "C" spanner rather than pin holes.

    Spindle Design 2a.png
    The drawing shows front and rear views of the spindle cap nut.

    Thanks Guys for your comments.
    Best Regards:
    Baron J.

  8. #233
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
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    Thumbs up Mini Boring bar !

    Hi Guys,

    In my previous post, I submitted a drawing of the end cap for the grinding spindle. That drawing showed several fine grooves that are part of the labyrinth dust trap !

    I've been giving some consideration to how those tiny grooves could be machined in what is basically a 12 mm diameter hole. Not having anything that I could make those grooves with, I decided to make a boring bar specifically to make them.

    05-04-2020-000.jpg 05-04-2020-001.jpg

    Needing something that would go through a 12 mm bore, I found that I had had a short piece of M10 threaded rod in the scrap box, so I used that. I milled the threads off two sides so that it would sit square in the lathe tool holder. That first picture is a family photograph of all the parts along with the Allen key for the M5 X 8 mm grub screw that I used for holding the tool bit.

    After milling the two flats I I milled two more short ones to form a square end. Notice that one flat is twice as long as the other side. This was done in order to ensure clearance when machining the grooves. I then drilled a 4.5 mm diameter hole 6 mm in from the end in order for the piece of 3 mm square HSS tool steel bit to go through and the M5 grub screw would clamp it firmly in the hole.

    I drilled and tapped the grub screw hole in the end by holding the bar vertical in the mill vice.

    05-04-2020-002.JPG 05-04-2020-003.JPG 05-04-2020-004.JPG

    These are pictures of the piece of 3 mm square HSS tool bit after grinding to size and shape. The end is 1.9 mm wide and 3 mm long. It is 7 mm long. I don't have any 2 mm HSS tool steel rod so this is a bit chopped off an 8" long (200 mm) rod. I used an abrasive disc and the Dremal to cut it off and shape it.


    05-04-2020-006.JPG 05-04-2020-005.jpg

    These two pictures show the finished tool along with the HSS tool bit in place. I rubbed the corners off with a file. All I need to do now is test that it works as intended.

    All thoughts or suggestions welcomed, thanks for looking !
    Best Regards:
    Baron J.

  9. #234
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    Dec 2007
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    Adelaide
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    It looks like it should work ok - as you say a test will see if it does work. When I did mine I ground down a 1/4" HSS lathe tool to the right shape - it worked ok, I recall that the problem is that you don't have a great view of the action happening and have no choice to but to go by feel, I know I made an allowance for tool spring but can't remember how much - it probably doesn't matter all that much as the dimensions are not that critical.

  10. #235
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    Nov 2017
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    Geelong, Australia
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    I think you might need to reduce the height of the HSS bit to make it close to the centerline of the bar.
    As it is, I don't think you're going to be able to get it on center in the work without the bottom of the bar hitting on the bore.

    Steve

  11. #236
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    Sep 2012
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    York, North Yorkshire UK
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    Hi Steve, Guys,

    Thanks for your warning ! An easy point to overlook.

    Actually that was one of my concerns and the reason for taking another shave of the bottom side and rounding off the corners with a file. If my measurements are correct then I should have about half a millimetre of clearance on the tool bit side. I can file some more off the corners if they rub.

    It was a right pain grinding that tool bit to shape, and just I've realised that I haven't put any top rake on it ! I was concentrating on getting the width right and side clearances, completely forgot about the top face.

    06-04-2020-001.JPG 06-04-2020-002.JPG IMG_0578.JPG

    I'm going to finish the drawing for this tool, then I will know exactly how much clearance I have.
    Best Regards:
    Baron J.

  12. #237
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    Sep 2012
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    Thumbs up Mini Boring Bar Drawing !

    Hi Guys,

    I've just finished the Mini boring bar drawing. I've shown a double size end view with everything centred on a 12 mm diameter circle. The small circle is the 5 mm grub screw. Using a 3 mm stick out for the tool bit it will come to the red line. So looking at the clearance at the top, it seems that it will only just fit without fouling.

    Actually the drawing is an idealised one since it doesn't take into account the filing that I've done on the edges !

    Mini Boring Bar.png

    I'll do a test on a bit of scrap later.
    Best Regards:
    Baron J.

  13. #238
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    Sep 2012
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    York, North Yorkshire UK
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    Thumbs up Cap Screw 1

    Hi Guys,

    I've made a start on the cap screw for one end of the grinding spindle.

    07-04-2020-001.JPG 07-04-2020-002.jpg

    I've drilled out to 11 mm and then bored the hole to 12 mm. I reduced the diameter to create the step and threaded the cap for a distance of 5 mm.

    Before anybody points out that the thread is too coarse for 32 TPI, it is ! Its actually 24 TPI. Because I forgot that I had set the lathe up for threading 1 mm TPI and forgot to change the spindle gear back to the original one. So selecting 32 TPI on the gearbox produced a 24 TPI thread. Good job I remembered to take the lathe off fine feeds, otherwise it would have been 62 TPI

    Anyway proof of the pudding, the special mini boring bar fits though the bore nicely, it just needs a bit filing off the bottom edges, although I could just move the tool bit down a millimetre to get the clearance.

    More to come Thanks guys.
    Best Regards:
    Baron J.

  14. #239
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    Dec 2007
    Location
    Adelaide
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    I see you have taken the end cap out of the chuck, is it a test piece ? do you think it would be wise to do all of the turning ie thread, bore and labyrinth seal grooves etc before removing the cap from the chuck, that way you can be sure every thing is concentric.

  15. #240
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    Hi Familyguy,

    Thankyou for your warning Though I don't have the problems that some people seem to have using a four jaw and test indicator.

    Yes it was basically to prove being able to fit the mini boring bar into the bore and machine the labyrinth grooves.

    This piece was parted off from a four inch length of 30 mm diameter bar held in the four jaw chuck. For a production piece I would machine the outside diameter to size for, say three times the length needed and then use the soft jaws to drill and bore through, then cut the step and thread it before parting off a 10 mm long piece. Repeat and part off the next piece.

    Using the soft jaws each piece should go back in the same position. This will allow me to be able to see both sides of the work when cutting the grooves. Another advantage of using soft jaws is you can put a step in them so that the work piece is held true in both directions.

    The next step would be to mount each piece on a mandrel and cut the spanner slots in them.
    Best Regards:
    Baron J.

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