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Thread: My homebuilt spindles

  1. #25
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    To make the tap, first a piece of silver steel was turned down and the end tapered. Then I turned the thread. I made a bit of a mistake there, the thread seemed a touch tight in the Proxxon collet nut which I used as a gauge. I just reran the same G76, and it took a little more off (spring cuts). This was a bad idea, as the final tap turned out marginally under size. I needed to run it back and forth in the brass a bunch of times before the nut would run down the spindle shafts thread.

    I used a spud to heat sink the shaft and keep it soft, while I heat treated the threaded portion. I only have one of those €10 hardware store propane cartridge burners, but it does fine with small things.

    Used the Proxxon in a QCTP holder (exactly the set up this spindle is being made to replace) to grind three flutes into the tap.

    To index the three flute, a DTI holder was set up with a scriber touching one for the tail stock drill chuck key holes. This way I just needed to retract the chuck till the taper ejected, and then rotate it with the scriber rubbing till it fell in the hole, and then extend the ram and force the chuck back in the taper. I first did the three cutting edges with a thin cut off disc, which made a nice sharp edge, and then removed the rest of the flutes with a normal grinding wheel.

    The tap came out okay (except for the under size issue). Since I didn't make the flutes very deep, you need to keep backing out often and clear the swarf.

    This is only the second home made tap I have ever made, and is the first one to work

    Attached Thumbnails Attached Thumbnails My homebuilt spindles-img_6609-jpg  
    Last edited by RotarySMP; 04-25-2010 at 05:17 AM.
    Regards,
    Mark


  2. #26
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    I always tend to look at the pictures first. This time I took a look, and I thought "what the..!?". Had to keep on reading! Never thought something like that would work. Good work!

    You gonna eat it?



  3. #27
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    The potato heat sink is as old as engineering. Works brilliantly. Kind of gummed up the scotchbrite cleaning fried spud off the tap though.

    I finished the peg wrench this morning.

    Next part is the first housing cap.

    Attached Thumbnails Attached Thumbnails My homebuilt spindles-img_6663-jpg   My homebuilt spindles-housing-cap-pdf  
    Last edited by RotarySMP; 04-25-2010 at 05:34 AM.
    Regards,
    Mark


  4. #28
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    I finished the first housing cap today.

    Not sure what steel it is, as it was a cheapo in the offcuts bin of metal supermarket. Certainly not a free machining steel. The best finish I could get on it is with a sharp HSS tool an almost no radius.

    Made a hash of the 3m radius. My lathe has lots of backlash on X. I should have cut the radius in from the OD, as then the tool would be loaded the whole way against backlash. Instead I cut it in from the ID, pulling on the QCTP to provide backlash compensation. It was going okay, until I slackened off a little. Therefore there is a groove in it.

    It is only a cosmetic feature. Kind of dumb have cosmetic features that look bad though

    Attached Thumbnails Attached Thumbnails My homebuilt spindles-img_6664-jpg   My homebuilt spindles-img_6665-jpg  
    Regards,
    Mark


  5. #29
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    Psh it looks fine It'll serve it's purpose just fine I figure



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    Thanks Jesse.

    Considering how differcult it is to get a decent surface finish on this steel, I am glad the thread came out nice. I ran the G76 three times before the thread cleaned up though.

    Considering the Proxxon IB/E has a single tiny ball bearing on the spindle shaft, and supports the rear end on the motor bearings. Making something significantly more rigid should not be a big challenge.

    I brought a box of about 20 FAG7200B.TVP AC bearings off Ebay. http://medias.schaeffler.de/medias/e...P;aiY4cjEcMLza
    I thought this would be a good project to start learning how to set up and preload a pair of AC bearings.

    Regards,
    Mark


  7. #31
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    I have now finished both caps and the housing. The housing took me about a week, as I really took my time to ensure no mistakes here. I used the Proxxon IB/E with cut off disks to grind the bearing seats. I have tried the Proxxon and Dremel grinding disks, but never got decent surface finish. With the cut off disks the finish was pretty good. You have to really sneak up on the final dimension and measure constantly, as the disks diameter is constantly changing.

    I changed the top housing cap a little, just to see whether I preferred a chamfer or a rounded corner.

    Attached Thumbnails Attached Thumbnails My homebuilt spindles-img_6669-jpg   My homebuilt spindles-img_6666-jpg   My homebuilt spindles-housing-pdf  
    Regards,
    Mark


  8. #32
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    Yeah, no way to precise grind with Proxxon and Dremel hand tools, at that without coolant. I made grinding spindle similar like milling spindle, just bit more simple - after that no problems anymore.
    And low feed and by wery tiny +steps you need to go on, even 0.05 is too much.
    I do use thin grain diamont wheels and burs. All grinding stuff must to be rigid and balanced. Im absolutely not a specialist - just my own expierence.
    regards,
    herbert



  9. #33
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    Hi Herbert,
    At the end, I was using .01mm step over (0.02mm off diameter) and doing three passes till it stopped sparking. This is pretty cool with the CNC. Although the machine is not accurate to 0.01mm, it does appear to be position repeatably at this level over small distances. This still leaves the wear of the wheel, so that I took ages sneaking up on that last tenth. I spent at least two hours yesterday doing three 0.01mm passes, measuring, offering up a bearing, and repeating for that last 0.1mm.

    Is it normal for AC bearings to have conical OD's? The FAG 7200B.TVP I have sacrificed to be my plug gauge has a taper of about 0.01mm, (0.0003") on the OD of it's outer race. As the bore opens up to the final tolerance, taper was very obvious, as the bearing would enter smoothly, and then jam as it approaches full depth. Reversed it would not enter the bore. I have the bore a nice stiction sliding fit of the larger bearing OD.

    Your recommendation of a small diamond wheel is a good one, so you don't have to chase the cut off disk wear.

    Making this spindle is great learning experience. I can see that a static balancing jig will be in my future. I would guess that there is little point focusing on dynamic balancing until I can static balancing things.

    Did you make your static balancing jig with the shaft rolling on razor blades?

    Regards,
    Mark


  10. #34
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    Quote Originally Posted by RotarySMP View Post
    Hi Herbert,
    At the end, I was using .01mm step over (0.02mm off diameter) and doing three passes till it stopped sparking. This is pretty cool with the CNC. Although the machine is not accurate to 0.01mm, it does appear to be position repeatably at this level over small distances. This still leaves the wear of the wheel, so that I took ages sneaking up on that last tenth. I spent at least two hours yesterday doing three 0.01mm passes, measuring, offering up a bearing, and repeating for that last 0.1mm.

    Is it normal for AC bearings to have conical OD's? The FAG 7200B.TVP I have sacrificed to be my plug gauge has a taper of about 0.01mm, (0.0003") on the OD of it's outer race. As the bore opens up to the final tolerance, taper was very obvious, as the bearing would enter smoothly, and then jam as it approaches full depth. Reversed it would not enter the bore. I have the bore a nice stiction sliding fit of the larger bearing OD.

    Your recommendation of a small diamond wheel is a good one, so you don't have to chase the cut off disk wear.

    Making this spindle is great learning experience. I can see that a static balancing jig will be in my future. I would guess that there is little point focusing on dynamic balancing until I can static balancing things.

    Did you make your static balancing jig with the shaft rolling on razor blades?
    I have dynamic balancer now
    Bearing seats I make often with turning as well (when stainless steel) - then for finishing I use Mitsubishi ID tool and very sharp inserts (for Alu). Making the spindle housing is complicated most of all because bearing seats on the both sides need to be very precise and very exact on the same axis. I do turn for every new spindle a special simple *one slot collet* and never take this "collet" out from lathe before both side bearing seats are ready (housing OD need to be finished to some adequate size before!).
    You know, Im 99% autodidact, perhaps I do use wrong tricks ... may be, but anyway my results come every time better and better. I dont know the terms and terminology, I dont like experts who carry out nicelly colored graphs and curves but never made his hands to dirty. But machinists who can show something I like very much, even when result isnt so good. Real Machinists I do adore! I never gainsay any machining method other machinists use, especially when their result is brilliant - I really do not know what is the final truth - does it exists at all
    Cheers,
    Herbert



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    Mark,

    Regarding balancing, are you aware of this site? http://www.technologie-entwicklung.d...cing_tool.html

    It might come in handy when you are ready to do some dynamic balancing. The second page contains a ZIP file with drawings etc...

    http://www.technologie-entwicklung.d...ble_parts.html

    bob



  12. #36
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    Hi Herbert,

    Could you please post a couple pictures of your collet setup?

    Did you see my question about conical OD of the bearings? I have never seen this before on the 6xxx series bearings I have used before.

    I know you have a dynamic balancer now, but what did you use for static balancing before?

    Regards,
    Mark


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