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What does 18.7 bore equate to ?

Discussion in 'Shooting Related Threads' started by pheasantsgalore, Feb 22, 2010.

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  1. pheasantsgalore

    pheasantsgalore Active Member

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    I don't have a bore measuring gaue, so what does a 18.7 bore measure......736 ?
    Thanks,.......Rob
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    Close enough, plus or minus a couple of thousandths.

    Neil
     
  3. short shucker

    short shucker TS Member

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    Bore diameters

    18.3mm = .720 inch

    18.4mm = .724 inch

    18.5mm = .728 inch

    18.6mm = .732 inch

    18.7mm = .736 inch


    ss
     
  4. claybrdr

    claybrdr Well-Known Member

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    My 34" Perazzi barrel is marked 18.7 and actually measures .740"
     
  5. Neil Winston

    Neil Winston Well-Known Member

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    That's why I wrote "plus or minus a couple of thousandths." A tenth of a millimeter is four thousandths. So 18.6 MM is not 0.732 inches. It is 0.730 to 0.734 inches.

    Neil
     
  6. EE

    EE Banned User Banned

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    I'm still trying to figure out why you need a bore gauge to do the math.

    EE
     
  7. Neil Winston

    Neil Winston Well-Known Member

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    I'll bet there once were a lot of people, EE, who wondered why you kept that slide-rule clipped to your belt. Or why you would go into the math-lab, type a number into the Merchant or Frieden, divide by zero and leave while it rumbled on and on looking for an answer for you.

    Neil
     
  8. halfmile

    halfmile Well-Known Member

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    Learned long ago a millimeter is 40 thousandths. Easy from there.

    HM
     
  9. Neil Winston

    Neil Winston Well-Known Member

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    An interesting characteristic of the 25.4 conversion is that it is exact. Even more odd is that its reciprocal, 0.3937, is also exact until you get down to a hundred-millionth.

    Neil
     
  10. g7777777

    g7777777 TS Supporters TS Supporters

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    2.54 CM = 1 inch as Neil said- its exact

    I think I may have a problem with missing because of wad rotation- I saw someone had a barrel for sale that was sure to prevent that?

    regards from Iowa

    Gene
     
  11. EE

    EE Banned User Banned

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    But a millimeter is not 40 thousandths, HM. And Neil, it's 0.03937. (Point ZERO three nine three seven)

    EE
     
  12. Neil Winston

    Neil Winston Well-Known Member

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    You are right EE. Thanks for the correction though I did have it right earlier.

    Neil
     
  13. Steve W

    Steve W Well-Known Member

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    If not because of us, this bloody "Standard" system invented by the English (who's smart enough to abandon it), would be gone by now. Maybe the old English had 12 fingers and 16 toes.

    Every time I'm helping a 4th grader to convert "standard" to metric, I feel sorry for the poor kid.

    Every time I'm trying to figure 3/16" or 9/64" is the next size, I curse the English.

    I have a Dial Caliper from "Frankford Arsnal Reloading Tools", it shows inches in 1/10th increments. How the xxxx I'm going to convert 1.80" = 1-4/5" on my "standard" ruler?

    Do you know you need two sets of tools to work on an American car?

    However, thank God one dollar is 100 cents, not 16 guineas.
     
  14. whiz white

    whiz white Strong Supporter of Trapshooting Banned

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    Divide by 25.4
     
  15. Neil Winston

    Neil Winston Well-Known Member

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    Steve, you needed _three_ kinds of wrenches to work on English motorcycles when they were on their deathbed. Whitworth, the old standard which were marked to match the size of the bolt they fitted (thus a half-inch wrench was huge), American which they drifted to whenever they ran out of one of the old ones or the last shipment was too shoddy even for them, and last, "gas" sizes which were used whenever a fluid was to be (partially - and only temporarily in the case of oil) contained - gas and oil lines, maybe here or there besides when the spirit moved them.

    I still have a box in a storage building labeled "Whitworth Wrenches" which some executor will open, turn over in his hands a couple of times, and toss into the dumpster and so will go yet another piece of industrial history.

    Neil
     
  16. EE

    EE Banned User Banned

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    Like working on a damn MG; a different wrench was needed for every nut or bolt.

    EE
     
  17. Neil Winston

    Neil Winston Well-Known Member

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    But that was actually a _feature_, EE. Morris Garage knew that few in Abington and Oxon environs would lash out for two wrenches of the same size - an obvious, needless, and spendthrift duplication. So they actually made sure that the two ends of a bolt had different sizes, giving you the opportunity to round off the flats in either 1/4W or 5/32W, whichever they could produce most cheaply with a mechanical strength similar to a good country cheddar.

    Neil
     
  18. EE

    EE Banned User Banned

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    MG tool = Vise Grips. No wonder they are out of business.
     
  19. Mapper

    Mapper Member

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    Even though inches convert to metric easily, feet do not. 1 meter equals 3,2808333.....feet, endlessly. The meter/metre is the length of a sine wave. The foot is the length of an Englishman's foot. Both are hard to find when it's late on saturday night.
     
  20. mx2k33

    mx2k33 Well-Known Member

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    18.7mm = 0.73622047 in
    = 0.06135171 ft
    = 0.02045057 yds
    = 0.00001162 miles
    = 0.00000000 light years
     
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