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Best way to fit these parts together.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Jmanb13, Apr 25, 2017.

  1. Jmanb13

    Jmanb13 United States Active Member Active Member

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    I have a bar that is ~.55 inches in diameter. I have a hole that is currently drilled out to 3/8 with drill bit.

    I want to turn down the bar and or enlarge the hole so that have a tight fit that is accurately centered and will resist radial forces. I assume that I would probably want to use a key to prevent slipping.

    What would be the best way to go about doing this?

    I do not have access to a mill or press.
     
    Guv likes this.
  2. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    Turn OD, bore ID and key both with a matching keyseat, done deal. Shafts and bores have been keyed together for well over 100 years.

    Otherwise crossdrill and pin together, you appear to have no other options.
     
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  3. Jmanb13

    Jmanb13 United States Active Member Active Member

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    Would boring or reaming the hole be a better idea in this situation? Keep in mind i'm still new to this, so I don't know when its better to bore vs ream a hole.
     
  4. coffmajt

    coffmajt H-M Supporter - Premium Content H-M Supporter-Premium

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    If you want a true hole then you must bore first, then ream to the diameter you want. Running a reamer through a hole that is not centered or true just gives you a smooth untrue hole == Jack
     
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  5. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    Boring is more accurate then reaming if you have the tools, if not ream away which will get you close enough for general purposes.
     
  6. chips&more

    chips&more United States Active User Active Member

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    If you want the best amount of strength out of the joint/marriage. Then you would want the bar to remain its nominal size and not turn it down at all.
     
  7. scwhite

    scwhite United States Active Member Active Member

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    As small as those shafts are
    You might consider drill and roll pin them together
    Instead of keying
    It all depends on how much force you plan on putting on that joint .
    Both of my machines the lathe and the mill
    Power feed is roll pins
    Bore your hole with a tight fit
    Heat the one with the hole in it .
    And freeze the other one that is turned down
    Push them together. Then drill a 1/8 hole and drive a roll pin in the hole .
     
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  8. scwhite

    scwhite United States Active Member Active Member

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    I don't think he has the ability to put keys in ether piece . Even if he did the key would have to be so little about 1/16" .
    Roll pin might be best for him
     
  9. Jmanb13

    Jmanb13 United States Active Member Active Member

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    I'm fine with using the roll pin as well. This is probably the best solution with my current tool capabilities :). Would secure the shaft in both radial and axial forces plus the shrink fit of the actual shaft should be plenty strong.

    Any suggestion on oversize/undersize on the hole to make the fit nice and tight with the shrink fit?

    This is 1018 steel btw.
     
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  10. scwhite

    scwhite United States Active Member Active Member

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    No more than .0005 press .001 is probably to tight
    You could just heat it a little and push it together
    Nice and tight. .0015 little more heat and even tight
     
    Last edited: Apr 25, 2017
  11. Toysinthehood

    Toysinthehood United States Steel Registered Member

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    Just make them the same size. No more, no less. They won't fit together if they are truly the same size. When I put rings on impellers, we heated the ring, a little loctite and done deal. (Dead Blow) that ring on and voila. I'm pretty sure you could bore it and use a cigarette lighter with the size. Is it rotating a certain direction? Threads?

    Sent from my RCT6513W87 using Tapatalk
     
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  12. Silverbullet

    Silverbullet Active Member Active Member

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    Pinning is easier and will work .
     
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  13. Jmanb13

    Jmanb13 United States Active Member Active Member

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    It will be spinning to the right, I am making a ER32 collet system for my drill press to turn it into a poor mans mill. I have already replaced the bearings in the quill with higher end double bearings that support radial and axial loads and now I am working on the driving shaft and collet chuck. In my research a 1/8 roll pin has a shear strength of between 1000 and 2000 lbs depending on the material. I would think that would hold up to the forces of a small end mill. After that I just need to add some adjustable brass slides to take the play out of the quill and add a cheap sliding table.

    At this point my milling is only for decorative effects so even if it has some runout it won't make a big difference to me.
     
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  14. scwhite

    scwhite United States Active Member Active Member

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    That should work just fine
     
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  15. Toysinthehood

    Toysinthehood United States Steel Registered Member

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    That sounds awesome. Could you take pictures as you go? What was the process for bearing selection and replacement? I might try this myself if pricing is good enough. Proxxon micro Mills are around $400 new.

    Sent from my RCT6513W87 using Tapatalk
     
  16. Jmanb13

    Jmanb13 United States Active Member Active Member

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    Yeah I'll take some pictures and see if I can put a little info together (assuming it works :) ).

    I bored out the quill to fit the new bearing last night and installed the bearing and put the stock shaft back in. At this point the run-out on the shaft without adding my ER32 chuck is less than 0.0005". My DTI goes down to 0.0005 and it barely wiggles when turning through a full turn.

    A this point I need to make my ER32 chuck and install it on the shaft, add a collet and end mill and see where I end up in run-out.
     
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  17. Randall Marx

    Randall Marx United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Sounds like this project is coming along nicely, Jman. I find this quite interesting because I have an old Craftsman drillpress that might make a good candidate for this type of conversion. I'll be watching for updates and eventually might need some advice/assistance. Thanks for sharing!
    -Randall
     
  18. NortonDommi

    NortonDommi New Zealand Active Member Active Member

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    Hello Jman.
    have you considered that slow tapers can transmit a lot of torque? All of the common tapers were developed by smart people and hard maths. It would take very little reinforcement such as a single grubscrew locating on a cone or into a seated taper surface to lock up to some very impressive numbers as to sheer. More power to your R.W.Y.H. approuch. Guys like you inspire us all.
    - Barry.
     
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  19. 4ssss

    4ssss United States Active Member Active Member

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    You can also shrink the shaft in by heating the part with the ID which will expand it. All you need is a .001 or so difference in diameters and the shaft will never release. I used to shrink carbide inserts into steel for eyelet press dies and never had one pop out.
     
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  20. Jmanb13

    Jmanb13 United States Active Member Active Member

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    I'm actually using my old 8" craftsman drill press as the donor. Worst case scenario I mess up a $75 drill press and lose a little cost in parts that could always be re-used elsewhere.

    I actually have! Infact I decided to use the original shaft and cut a J33 taper on the chuck. Then I will drill and secure it with a roll pin to keep it from popping off. No reason to re-create a part that is already done :). The taper plus the roll pin should be completely adequate to hold everything together safely and securely.
     
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  21. Highsider

    Highsider United States Active Member Active Member

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    A key way will prevent tortional slippage and a Cross pin will resist axial slippage. If you are satisfied with the location of the 3/8" drilled hole, drill it out to 31/64" and then run a well lubricated half inch reamer thru it. Then turn and polish the shaft end to .0002" or so tighter (larger) than what the reamed hole came out. (Requires careful measurements). Key
    seat both the hole and the shaft if you want it keyed and deburr them. Mount the key in the shaft and chill it(a freezer will do, but CO2 would be better.) Heat the reamed piece in an oven or with a torch if you can control the heat well enough to keep it from discoloring. Clamp the shaft in a padded vise with the key in the vertical position and using hot gloves, line the keyway up and slide it together. Work quickly so they don't transfer too much heat and stick before they're where you want them. Two ten thousandths of an inch interference fit is about standard for 1/2" diameter interference fits. If you're going to cross pin the fit, do it last. The half inch fit is the strongest you can do with what you've got and using a standard reamer. Good luck.
     
    Last edited: May 1, 2017
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  22. AGCB97

    AGCB97 United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Depending on the use and torque transmitted between the two, Locktight 620 is strong and very easy. Or I've seen youtubers silver solder things like this
     
  23. whitmore

    whitmore United States Active Member Active Member

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    If you had a suitable tapered reamer, and could match its taper on the end of the bar,
    that will center it and resist radial force. Jeweler's wax or other adhesive would
    keep it in. If the fit is good, superglue can hold a ton.
     

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