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  1. #1
    Ray Behner's Avatar
    Ray Behner is offline Titanium
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    Default Shaft keyway depth calculator

    For those of us that machine the bigger key cuts in shafting that's not in the MHB, here's a neat calculator:

    Shaft Keyway Depth Calculator - CNCexpo.com

  2. #2
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    I was taught that the keyway depth was 1/2 the key height in the shaft and 1/2 the height in the gear hub or mating part.

    What am I missing?

    - Leigh

  3. #3
    Ray Behner's Avatar
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    Leigh,
    All this does, is calculate the radius height that is added to the dim. of the key. That dimension changes with the diameter of the shaft and width of the key. Just did a 7/8'' key in 3.4375 shaft. .4375 + .057 = .4945. That's how far you go down after touch off.

  4. #4
    kevin johnson's Avatar
    kevin johnson is offline Cast Iron
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    My favorite Uncle gave me the formula : Endmill squared divided by 4 X Shaft = radius segment height of key-way.


    I have not seen it else where but it works for me. Hope it makes sense to

    someone else.

  5. #5
    Forrest Addy is online now Diamond
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    The depth of the keyseat is measured where the width intersects the shaft diameter measured from a theoretically sharp corner. That's the theory. You have to go deeper from first contact where the cutter first brushes the diameter then sink by what geekspeak calls: "Chordal height of the arc subtended by the keyseat width" Machinery's Handbook gives clear directions for calculating this. It's worked for me for 50 years by gum hee hee (thigh slap)

    If someone went to the trouble to cook up a nice little app fine. I'm all for it. A slick algorithm like Ray posted is cool too. A table, a spreadsheet in your laptop, there's tons of ways to do what was one of the first problems posed in my trade apprentice math class - and that was before pocket caalculators. We had to calculate long hand or with logarithms..

    Whenever I had to end mill or side mill a keyseat I usually got lazy and sunk the cutter 'til the corners intersected the shaft diameter then I dialed into the shaft 1/2 the key height (remembering the clearance goes in the keyway of the mating bore.)

  6. #6
    Abom79's Avatar
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    Thats a cool find Ray. Thanks for sharing. I might use it to make a simple chart to keep in my shop book. I cut keyways all the time and always use the feel method of finding when the cut is completly flat. Someone needs to make this a phone app.

  7. #7
    Greg White is offline Titanium
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    hows aboot moving half the key witdh and half your cutter dia. ,touching off and calling it done,plus .005 or .010 on a larger key?
    Gw

  8. #8
    Ray Behner's Avatar
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    Quote Originally Posted by Greg White View Post
    hows aboot moving half the key witdh and half your cutter dia. ,touching off and calling it done,plus .005 or .010 on a larger key?
    Gw
    Hey, that's cheatin'! But you can get darn close that way.

  9. #9
    DMF_TomB is offline Titanium
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    Default keyway chordial distance calculator and speed and feed

    added keyway distance from top calculator to free Excel file. Excel is easily able to do mathematical equations in milliseconds. it is my belief all 21st century machinist should be taught the basics of using Excel or the free Open Office Calc program
    .
    also update speed and feed calculator with plastic data. i find horsepower required to cut plastic compared to steel is roughly 1/12. this vastly changes depth of cut and feed when cutting plastic like uhmwpe. heat buildup data still suggests vastly higher cutting rates end milling by periodically pulling cutter to allow cutter and workpiece to cool. even at 75% cooling time 1/4 at 10x rate is still 250% faster machining rate than normal.
    .
    i find my machining times are vastly faster by scientifically calculating the optimum parameters based on conditions which Excel can calculate in milliseconds. Remember calculator adjust speeds and feeds based on conditions. For example chip thickness is vastly different with aluminum compared to stainless steel. feed and depth of cut is adjusted by cutter length, coolant, length of time cutter is in how deep a slot, etc. i also increased horsepower a Bridgeport Series 1 mill has to 1.5hp. all horsepower calculations are tested by stalling the motor on a Bridgeport type mill. I find machining at 1.5 hp rate requires an extremely good vise or clamping setup or workpiece will move causing damage.
    Attached Thumbnails Attached Thumbnails keywaycalculator.jpg   calculatormay28.jpg  
    Attached Files Attached Files

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    Quote Originally Posted by Forrest Addy View Post
    Whenever I had to end mill or side mill a keyseat I usually got lazy and sunk the cutter 'til the corners intersected the shaft diameter then I dialed into the shaft 1/2 the key height
    That's what I was taught. Didn't realize it was being "lazy".

    - Leigh

  11. #11
    Abom79's Avatar
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    Quote Originally Posted by The real Leigh View Post
    That's what I was taught. Didn't realize it was being "lazy".

    - Leigh
    Thats the way I was taught, and the way we do it in our old greasy job shop...... Most of the shafts I build are not that critical. The jobs that are, I use a depth mic to get them spot on.

  12. #12
    Greg White is offline Titanium
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    Cheatin is how I get "A"s in maachinin,my shops in a barn.
    Gw

  13. #13
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    Don't forget to allow for any grind stock that might still be on the shaft when you touch off.

  14. #14
    Heavey Metal is offline Titanium
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    What is handier is a measurement of from the bottom of key to the backside of shaft. (Easy to measure with a mike). I always put this measurement on my drawings. You can take a cut measure the remainder , do the math ,set the dro and here we go. Just one more step from your chart. Neat calculater faster than the formula in machinery handbook. Thanks

  15. #15
    AHS
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    Quote: "Excel is easily able to do mathematical equations in milliseconds. it is my belief all 21st century machinist should be taught the basics of using Excel or the free Open Office Calc program."

    I'm very supportive of using spreadsheet programs also, and appreciate folks like yourself who share their work. However I would suggest that you provide a little documentation on each of the sheets. It makes it easier to see what you've done and how you did it. Maybe even the formulas since there usually are several ways to calculate any given number.

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