press fit drill and reamer size help
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  1. #1
    Join Date
    Aug 2004
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    North Central Indiana
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    press fit drill and reamer size help

    Guys I need to make two 1"OD X 2" long brass shoulder bushings with ID's of 3/4" but I am confused on the drill sizes and reamer sizes I need to buy.

    Here's my questions:

    I need to know the proper drill size to ream a 3/4" axle hole in brass.

    I also would like to know the proper drill and reamer sizes I need to buy to have a press fit in steel for the 1" OD brass bushings.

    I appreciate any instructions you may offer me for drilling and reaming the holes,Thank you. :help

    Picture is of the 36" long X 2.375 round the bushing bosses will be made from. got it for $15 which I thought was a good price. I wanted 3" but they didn't have salvage 3".
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    Last edited by tackit; 07-16-2013 at 07:35 PM.

  2. #2
    Join Date
    Mar 2013
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    19

    Re: press fit drill and reamer size help

    Generally speaking you want to leave about a 1/64th of an inch UNDER the finish size of the hole. So for the 3/4inch id you would want a 47/64ths drill. The size reamer for the same hole will depend partially on the actual size of the axle shaft. I would suggest .005 (five thousands) of an inch larger than your shaft size. So if the shaft is .750 exactly you want a .755 Diameter reamer. For the press fit hole you have 2 choices, either oversize the OD of your bushing or undersize the hole the bushing goes into. I would suggest oversizing the bushing and make the receiving hole a true 1.000 diameter (use a 63/64th diameter drill and 1.000 reamer). I would make the bushing 1.002 for a nice tight press fit. Keep in mind however that this will likely close down the ID slightly. My suggestion would be this, drill receiving hole for bushing, ream to final size. Drill undersize ID hole in bushing material, turn OD of bushing to press fit size, press bushing into recieving hole then ream the ID of the bushing to final size with bushing installed.

    Hope all of that made sense.

    Chris.
    Last edited by NC_Machine; 07-16-2013 at 09:25 PM.

  3. #3
    Join Date
    Aug 2004
    Location
    North Central Indiana
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    2,529

    Re: press fit drill and reamer size help

    Quote Originally Posted by NC_Machine View Post
    Generally speaking you want to leave about a 1/64th of an inch UNDER the finish size of the hole. So for the 3/4inch id you would want a 47/64ths drill. The size reamer for the same hole will depend partially on the actual size of the axle shaft. I would suggest .005 (five thousands) of an inch larger than your shaft size. So if the shaft is .750 exactly you want a .755 Diameter reamer. For the press fit hole you have 2 choices, either oversize the OD of your bushing or undersize the hole the bushing goes into. I would suggest oversizing the bushing and make the receiving hole a true 1.000 diameter. I would make the bushing 1.002 for a nice tight press fit. Keep in mind however that this will likely close down the ID slightly. My suggestion would be this, drill receiving hole for bushing, ream to final size. Drill undersize ID hole in bushing material, turn OD of bushing to press fit size, press bushing into recieving hole then ream the ID of the bushing to final size with bushing installed.

    Hope all of that made sense.

    Chris.
    That's exactly what I have been looking for Chris, thanks a ton.

  4. #4
    Join Date
    Mar 2013
    Posts
    19

    Re: press fit drill and reamer size help

    Anytime man, happy to help. One more final tip, new reamers tend to cut off size for the first few holes. If you have the material to do it, drill and ream a few practice holes before doing the important work. It may save you some grief in the end. Practice holes don't have to be in the same material btw, so save the bushing material and ream a few holes in some extra scrap steel.

  5. #5
    Join Date
    Aug 2004
    Location
    North Central Indiana
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    Re: press fit drill and reamer size help

    Quote Originally Posted by NC_Machine View Post
    Anytime man, happy to help. One more final tip, new reamers tend to cut off size for the first few holes. If you have the material to do it, drill and ream a few practice holes before doing the important work. It may save you some grief in the end. Practice holes don't have to be in the same material btw, so save the bushing material and ream a few holes in some extra scrap steel.
    Thanks again Chris.

  6. #6
    Join Date
    Feb 2009
    Location
    Central Illinois
    Posts
    437

    Re: press fit drill and reamer size help

    Be aware when drilling brass to drill to the size you want the first time. Brass wants to suck your drill in if trying to increase a hole size or drilling with a pilot hole. Drill out to 1/64 or 1/32 under your reamer size then ream. Drilling on a lathe helps a little but will still try to suck the bit in.

    Dan

  7. #7
    Join Date
    Aug 2004
    Location
    North Central Indiana
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    Re: press fit drill and reamer size help

    Quote Originally Posted by DanD78 View Post
    Be aware when drilling brass to drill to the size you want the first time. Brass wants to suck your drill in if trying to increase a hole size or drilling with a pilot hole. Drill out to 1/64 or 1/32 under your reamer size then ream. Drilling on a lathe helps a little but will still try to suck the bit in.

    Dan
    Thanks Dan, I'll remember that.

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