Could I get two gears cut by a forum member?
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  1. #1
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    Default Could I get two gears cut by a forum member?

    I would like to purchase two helical gears from a forum member. These need to be hobbed on a gear hobber that uses manual change gears.

    Below shows the specifications. I am interested in having the leads checked, too.

    I want to specify what change gears to use based on the gear cutter's index and feed constants (it's a test). These could be cut out of 360 brass or anything that machines easily and maintains its shape (not nylon).




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    I have to ask how in the world it has a DP of 20 but a TP of 2

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    Quote Originally Posted by johnoder View Post
    I have to ask how in the world it has a DP of 20 but a TP of 2
    transverse pitch diameter. oops.

    I updated those photos after John pointed out my mistake in nomenclature.
    Last edited by David_M; 09-02-2019 at 09:43 AM. Reason: Correct mistake

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    Might be a little hard to hold that precise helix angle...

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    Even if I allowed + or - 1 on the last digit?



    Whoever wants to do it can ignore the excessiveness and make it using their normal shop practices. I'm easy to please and I pay in american.

    I made it like that to copy/cut and paste between it and the windows calculator without truncating values.

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    American Machine & Gear Works

    This guy is a Forum Member, under username Zahnrad Kopf <--- I probably butchered the proper spelling. Anyway, shoot him an RFQ.

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    Quote Originally Posted by Jashley73 View Post
    American Machine & Gear Works

    This guy is a Forum Member, under username Zahnrad Kopf <--- I probably butchered the proper spelling. Anyway, shoot him an RFQ.
    Jashley73 beat me to it.

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    Quote Originally Posted by Jashley73 View Post
    American Machine & Gear Works

    This guy is a Forum Member, under username Zahnrad Kopf <--- I probably butchered the proper spelling. Anyway, shoot him an RFQ.
    Another vote for WJ. He is a true gear head that makes great parts and is fantastic to deal with.

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    We have a fairly new hobber that is about 5 years old, so the feed screw is in great shape and not worn. I would suggest making the face width on each gear at least 1" wide so you can get a good measurement on a lead checking instrument. We can also verify the lead after cutting if you wish. PM me if you have no other offers.
    Dan

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    Quote Originally Posted by Dan from Oakland View Post
    We have a fairly new hobber that is about 5 years old, so the feed screw is in great shape and not worn. I would suggest making the face width on each gear at least 1" wide so you can get a good measurement on a lead checking instrument. We can also verify the lead after cutting if you wish. PM me if you have no other offers.
    Dan

    Thanks Dan. I'll PM you, shortly.

    Best regards,

    david

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    mail box cleaned out. Dan

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    PM Sent...

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    Quote Originally Posted by David_M View Post
    PM Sent...
    I apologize for not seeing this thread. Someone actually sent me a link to it. David, you are in good hands with Dan. In the future, please feel free to email me directly. You should still have my email, from a month ago. If not, don't hesitate to PM me for it.


    Quote Originally Posted by Jashley73 View Post
    American Machine & Gear Works
    This guy is a Forum Member, under username Zahnrad Kopf <--- I probably butchered the proper spelling. Anyway, shoot him an RFQ.
    Quote Originally Posted by AARONT View Post
    Jashley73 beat me to it.
    Quote Originally Posted by J Gilles View Post
    Another vote for WJ. He is a true gear head that makes great parts and is fantastic to deal with.
    Gentlemen, thank you, each. I sincerely appreciate the vote of confidence and support. That is incredibly humbling.

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    Hey Guys- if you already have a relationship working together, I have no problem stepping aside. Dan

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    Quote Originally Posted by Dan from Oakland View Post
    Hey Guys- if you already have a relationship working together, I have no problem stepping aside. Dan
    It's no intrusion at all. Honestly.
    I'm going to help him with another effort, so there's no toe stepping going on. Hob away!
    Besides, if I'm honest, we are positively buried in gear work right now and I do not know when the machines will have have open time for the forseeable 6 - 8 weeks. ( the other machines aren't resting much either )

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    I know some people who cut helical gears (not talking about anyone on here) will scoff at the notion of having a C constant in any form other than a whole number.

    I want to prove that that concept is wrong.

    example:



    Here the C constant has a repeating decimal of .45... (I could change it so it only shows fractions)

    That means the fractional form is 18 45/99 (just like .3... = 3/9 = 1/3 or .6... = 6/9 = 2/3).

    Below it is worked out using only fractional math to prove it is exactly equal:



    By using these, it gives many more options. Compared to sample results in books and on the internet, these are two, three or more decimal places more accurate.

    I've added multi-threaded processing too. Now that I have it at this point, I want to use this framework to do a program to use the differential to cut primes. Hoping to get some good results.

    64bit win 7+: https://1drv.ms/u/s!AjRYB9hC1AwChtBl...eKq1w?e=VBgiqT

    32bit winxp: https://1drv.ms/u/s!AjRYB9hC1AwChtBk...9K0tA?e=VKi3AZ


    Try it and let me know what you think. PMs emails fine.

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    The concept is indeed wrong. The spreadsheet that I made does much the same thing and I've been using it for longer than I care to think about. Whole numbers are just convenient for most people. And all the fractional constants gain one is the ability to have a larger pool of gears to choose from to create the train. As long as the two combined results have the accuracy required, it does not matter.

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    Here's one where the C constant is 9.9453125

    In fractional form it is: 9 9453125/10000000

    30 * 9.9453125 / (41 * 9.9453125) - 1 =

    30 * 99453125 / (41 * 99453125) - 10000000 =

    2983593750 / 4077578125 - 10000000 =

    2983593750 / 4067578125 =

    38 * 67 * 1171875 / 89 * 39 * 1171875 =

    cancelling 1171875 leaves:

    38 * 67 / 89 * 39

    These all work out identically (absolutely perfect index gearing). This is all built into the program I posted.

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    In my experience, as long as the feed constant is exactly the same for both the index and feed gear calculations, it should work. As long as the feed constant will allow an exact index ratio to be selected, life will be good. Most times there is error in the feed gear ratio at the 5th, 6 or 7th decimal anyway, but the lead error introduced is so small, we never see it.

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  24. #20
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    So are you going to get some gears, or argue ?....

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