Is it possible to reduce a .192 dia. hole to be a proper fit for a .187 dowel pin? - Page 2
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  1. #21
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    Quote Originally Posted by Punkinhead View Post
    Why are you making random sized holes and hoping the mating pin fits? Does the customer not supply a toleranced drawing? How do you know the diameter of the customer's pins aren't all over the place?
    I have worked with the assembly guy on fits and tolerance issues in the past by request of the owner. I don't know the dowel pins are all the correct size but it is time to sort it out.

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    Probably not practical, but worth mentioning since no one has to this point—-electroplating. If these are high value parts, it could be worth the trouble and expense.

    The practical solution probably is to bore out the holes over size, plug and re-bore. The problem with that is the fact that the pin is a driven fit. If you later drive out the pin, does the sleeve stay or come out with the pin? So your approach has to be you bore, tap, plug with a fine threaded plug, loctite, bore? Will boring a big enough hole to tap distort the straightness of the shaft?

    Denis

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    I would second plating the hole. .002 thick nickel would do the trick

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    The problem with plating is he still doesn't know what size the holes need to be. So now he's spent money on plating and doesn't know what size to ream them to.

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    Quote Originally Posted by Punkinhead View Post
    The problem with plating is he still doesn't know what size the holes need to be. So now he's spent money on plating and doesn't know what size to ream them to.
    I am confident he will soon have an answer to what size the hole needs to be. Without that answer, how does he make any correction to the problem?

    Denis

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    Probably not doable since the part is finished but when steel is heated to red it shrinks smaller than its original size after cooling. Maybe it would shrink the hole enough? But the OD size would also shrink so.... Discuss with a heat treater to see if possible.

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    Quote Originally Posted by moonlight machine View Post
    I have worked with the assembly guy on fits and tolerance issues in the past by request of the owner. I don't know the dowel pins are all the correct size but it is time to sort it out.
    Agree THAT for-sure.

    Got a decent working relationship, the lot of you sit down over a bench, yah might take a whole new approach as ain't so problematic to begin with.

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    I'm sorry you are in this mess, I have the feeling you are going to be making these over unfortunately. There's just no surefire way to remedy this.

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    Quote Originally Posted by Larry Dickman View Post
    I would second plating the hole. .002 thick nickel would do the trick
    Good in theory, though Nickel might not be first-choice, where high, fast, build for retention is all yah need.

    NOT so good in practice, time you mask, electro-clean, and work down a hole, tiny - entire REST of the part meant to be untouched.

    Folk as are any GOOD at that don't exactly work for free, the metals cost not really a significant factor vs labour where not enough unit-count to automate.

    That small? A Loctite-tribe critter will work as well. Those ARE amenable to economical onsies and fewsies.

    "Money" vs function wise, I suspect it's linear-rib the hole.. or remake the part.

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    To OP:
    You said in contact with owner and good relations.

    Electroplate with whatever brew.
    Ream suitably undersize.
    Charge suitably for next set.

    Explain all 3 to owner, up-front.

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    I have seen holes close up a slight amount after heating then and cooling them quickly, not sure if the heat would cause you more problems or not.

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    I'm not the world's most precise type of dude, but all the knurling and peening and burring and other half-ass methods of making a tighter fit are pretty lame. We all know they are band-aid fixes that aren't sound work.

    I'd talk to the customer and find out 'if' they can live with the above type repairs...I guess it's possible the fit might not need to be permanently tight or on-center. But if they can't, then it's new shaft time or possibly 'hot' remedy (like welding or electro-spray).

    Most of all...it sounds like your customer is not giving you enough proper direction and expecting you to produce miracles that make everyone happy....

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    Quote Originally Posted by GregSY View Post
    I'm not the world's most precise type of dude, but all the knurling and peening and burring and other half-ass methods of making a tighter fit are pretty lame. We all know they are band-aid fixes that aren't sound work.

    I'd talk to the customer and find out 'if' they can live with the above type repairs...I guess it's possible the fit might not need to be permanently tight or on-center. But if they can't, then it's new shaft time or possibly 'hot' remedy (like welding or electro-spray).

    Most of all...it sounds like your customer is not giving you enough proper direction and expecting you to produce miracles that make everyone happy....
    Without knowing what the tolerance on the print was there's no way to place ultimate blame.

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    Quote Originally Posted by moonlight machine View Post
    It is a hard dowel pin.
    It will work with a hardened pin and displace metal somewhat like an arc welder. I've also used one to score a line around a carbide blank to snap it off to a certain length.

    Looking around I see they are usually called an electric arc pencil.

    YouTube

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    Quote Originally Posted by Punkinhead View Post
    The problem with plating is he still doesn't know what size the holes need to be. So now he's spent money on plating and doesn't know what size to ream them to.
    Electroless Nickel plating thickness is very predictable and constant. I would be reaming the bores to all the same size, have the client sign off on a bore size (with tolerance) and Electroless Nickel plate to size.

    Regards,

    Bill

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    Quote Originally Posted by angelw View Post
    Electroless Nickel plating thickness is very predictable and constant. I would be reaming the bores to all the same size, have the client sign off on a bore size (with tolerance) and Electroless Nickel plate to size.

    Regards,

    Bill
    depending on the complexity of the parts, another alternative would be to plate the pins.

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    Quote Originally Posted by Larry Dickman View Post
    depending on the complexity of the parts, another alternative would be to plate the pins.
    Somewhere in the middle of the thread he said the pin mated with a .190" slot so plating the pins won't work.

    I would recommend the 5mm form tap as well if Loctite is a no go. Might need to play with different H numbers to get the right fit.

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    Quote Originally Posted by bigjon61 View Post
    Somewhere in the middle of the thread he said the pin mated with a .190" slot so plating the pins won't work.

    I would recommend the 5mm form tap as well if Loctite is a no go. Might need to play with different H numbers to get the right fit.
    well no shit, only plate half the pin, or plate the whole pin and grind the plating off one side. Figure it out

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  21. #39
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    How could ANYONE PRESS a pin into this off center hole? It is hard enough to start a press fit pin on a round shaft when it is ON CENTER.If this must be done,there needs to be a stepped pin or a stepped lead hole so that the poor assembler can put the stupid thing together. You are dealing with an incompetent engineer. Edwin Dirnbeck

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    How did you make this hole? Don't tell me you tried to ream it. Edwin Dirnbeck


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