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Tooling question: List of Diameter Sizes?

  1. Dec 2, 2007 #1
    I've been working on a tooling Design project for a unique part, basically I'm taking a cast metal piece and drilling and reaming it to be used as an oil flow passage for a Harley Motorcycle. I.e. I'm the (student) engineer that is designing the jig/fixture device to be able to do the work.

    Everything was running smoothly until I came across a hole that has a pre-reamed Diameter (Theta) "X" and a reamed diameter of (Theta) "Z." Each of those come with a tolerance of +/- 0.0005.

    Does anyone know what size they are (roughly)? Or does anyone know of a link that has a list of diameters?
  2. jcsd
  3. Dec 2, 2007 #2


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    Hi kahless,
    Not sure if you're asking about a list of standard reamer sizes or where you might be able to purchase them.

    If you're asking about standard sizes, I'm not sure there is a list. They come in just about any diameter you want. If it isn't available in some size, you can either have them made, or a standard one can be ground down to your specific diameter. Generally you don't need to take but a few thousandths of an inch off

    If you're looking to purchase one, I'd recommend McMaster Carr here:
    I use them all the time to purchase parts for various projects I work on. Cost is good and shipping is generally overnight.

    To find a specific reamer, just type in "ream" and you can locate just about any size reamer you'd like. Generally, you can get any diameter to the nearest 0.0005" up to about 1/2" and then it jumps around a bit above that point.
  4. Dec 2, 2007 #3
    Not Quite what I was looking for, but a search of the website yielded what I needed.

    Thank you
  5. Dec 2, 2007 #4
    Is this a dimension you've put down or what someone else gave you? Since you found the answer at McMaster-Carr, I'm assuming what you figured out is to drill dia 0.3970 and ream to dia 0.4130. If that's right, there are 3 points to think about:

    (1) If you're going to ream the hole, why such a tight tolerance on the drilled hole? And, you'll probably have to ream that hole anyway just to hold that tolerance.

    (2) The difference in hole diameters is 0.016. Depending on the metal, that may be a lot for reaming.

    (3) You shouldn't dimension a reamed diameter by a twist drill size ("Z"). Give the diameter you want in decimal form.
  6. Dec 2, 2007 #5
    Those were the dimensions given to me.

    I'll bring the three point up to the professor.
  7. Dec 2, 2007 #6
    No point showing him up - just cost you points. That's why I asked if it was your dimension.
  8. Dec 2, 2007 #7


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    A pre-reamed hole diameter to a half a thou? Someone's smoking something.
    Last edited: Dec 3, 2007
  9. Dec 3, 2007 #8
    I used to work with a machine shop where they loved stuff like that. Whenever drawings had extraordinary tolerances or weird GD&T, they would just double or triple the price and then do it the same way they always did. If the purchasing agent questioned the high price, the machinist would point out the tight tolerances. The engineers, most of whom wouldn't know a Bridgeport if one fell on them, thought they were achieving high precision.
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