go to the page above “Helical milling – links”

Hobnail – software for computing gear trains.

Hobnail was written by Gareth Evans specially for computing gear trains for hobbing helical gears using a modified Jacobs gear hobber. For helical gear hobbing two gear trains are needed to a very high  degree of accuracy. But it can be used perfectly well for designing any sort of gear train.

This software is written in VBA in an Excel spreadsheet. It is not available on the web.

If anyone thinks they might need a copy get in touch with me via the comment facility at the bottom of this page.

When Hobnail is first loaded it is essential that the macros are enabled.

The next step is to load onto the second page the gears that are available. If different sets are available then they can be stored on other pages and copied as required onto the second page. These numbers can be stored in any place and in any order.

 Using hobnail to design a simple gear train

At the top of the spreadsheet it says “freehand gear calculator” click this is you just want to make a single gear train for whatever purpose.

A case of this might be a gear train for helical milling. When doing this the gear set available might be very limited and the accuracy is not going to be very good. But for helical milling the required accuracy is not great. It is worth remembering that the lead required depends on the diameter of the workpiece and for this the average between the top and bottom of the cut is used.

 Designing two trains for hobbing

When hobbing it is necessary to have two gear trains. Any error in either of these trains is accumulated over a very large number of rotations of the hob. It is therefore necessary for both trains to be very accurate. It is not possible to do this with the standard sets that are supplied with a lathe or dividing head. It is necessary to have a full set from , say, 20 to 120 as would have been supplied with a gear hobbing machine before electronic means were used.

The chances of the ration being perfect are zero. This means for any particular ration required there will be two choices, one that is higher that that required and one that is lower. This is true for both trains. This does mean that choices can be made that can improve the accuracy.

The rate at which the workpiece is passed over the hob, ie, feed, does not affect the accuracy of the gear but it does affect the choices of gears that need to be used.


  1. Dave said:

    I would like a copy of the Hobnail spreadsheet please

    • If I can find your email ad I’ll send you a copy.

      john f

      • paul mayhead said:

        Hi John
        Could I please have a copy of your Hobnail software?
        Thank you paul

      • johnf said:

        I think I have sent you an email with it as an attachment.
        Let me know if you have any problems with it.
        john f

  2. John said:

    Hi John, I would like a copy of you hobnail spread sheet please, as I am trying to cut a pair of helicoil gears and your spreadsheet sound just what I need,many thanks

    • johnf said:

      Are you using a milling machine or a gear hobbing machine. Hobnail is best for working out the gear ratios for a hobbing machine. If you are not using a hobbing machine the whole process is much simpler especially the maths and there is only one gear train and its accuracy is not critical.
      see my page on making helical gears on a vertical milling machine. Yuo can only use a horizontal machine if it is universal ie its table can be swivelled .

      hobnail can be used to calculate just a single gear train and is especially useful in that you can tell it the gears you have available.
      I need your email address to send you hobnail.
      john f

  3. Mike Beaston said:

    Great web site. I am designing a quick change gear box for a Mini Lathe. I would love to have a copy of your Hobnail program/spreadsheet. MikeBeaston@yahoo.com

    • johnf said:

      I’m emailing you a copy.
      john f

  4. paul cummins said:

    hiya john, plaese can i have a copy of the hobnail spreadsheet, thank-you

    • johnf said:

      Can you send me your email address.
      john f

  5. Amol Walde said:

    Please help me with hobnail software.

    Thanks in advance

    • johnf said:

      I can send you a copy if I have your email add.

    • johnf said:

      Did you get the copy hobnail?


  6. Danish Hanif said:

    Please send me Hobnail spreatsheet

  7. Jim Simpson said:

    Hi John , I have been trying to figure out how to cut helical gears on my lathe . I use change wheels(gears) for screw cutting.
    I would be very grateful if you could send me the spreadsheet for calculating gear trains please.
    Regards, Jim

    • johnf said:

      I need your email address if you want a copy of hobnail.
      Since I dont have a page on making helical gears on the lathe I shall write it up as far as I can and let you know.

    • johnf said:

      dont forget to enable macros

      john f


    • johnf said:

      did you get this?

      john f


  8. paul mayhead said:

    Yes thank you very much. It will save me a lot of brain power!


    I’ve been tooling up to try my hand at cutting helical gearing and hobnail sounds like it would be very useful. I would appreciate a copy of it please

  10. Mersudin Kevric said:

    hello you helped me a lot my e-mail is mersudi40@gmail.com if you can send me a Hobnail i would be thankfull.

  11. Peter Watson said:

    Hi, I’m not sure if this thread is still active, if it is I would be grateful if you could send me Hobnail. I am in the initial process of building the Jacobs machine based on drawings from CES. Regards, Peter Watson, Australia.

    • johnf said:

      send me your email add and I will send it to you

  12. Hitesh sharma said:

    hello, you are a genius person. helped everyone a lot. am from India. have a zeal to learn gear technologies. can you plz help me. reply me at
    mail- hitesh_sh1010@yahoo.com

    • johnf said:

      If you have a question you can put it as a comment.
      john f

  13. Amr Abdo said:

    Dear John,
    I hope you can send me a copy of Hobnail.
    I appreciate your efforts.

    Best Regards,,,

    Amr from Egypt

    • johnf said:

      I have emailed it to you.

      john f

  14. Irby Jones said:

    Hi John. Would you please send me a copy of Hobnail. I’m going to do helical milling using a universal mill set up with a dividing head just like you did on your vertical mill. Thanks.

    • johnf said:

      I cant see where your email address is.
      john f

      • Irby Jones said:

        I filled it in where it had a spot but maybe it didn’t show you. Here it is:
        irbyrat at yahoo dot com

  15. John Towns said:

    Hi John. please send me a copy of Hobnail if you would be so kind. Thank you very much!

    • johnf said:

      I have just noticed that comment like yours no
      longer get sent to me at Hotmail. I looks like I am meant to use gmail!
      See if you can email me at johnsf23@hotmail.com

      john f

      • froibel torres said:

        dear sir john can i ask a copy of your hobnail i havent recieve last time. my email is torresfroibel@gmail.com

  16. William H. Fissell IV said:

    Hi, I have a dividing head but not rhe gear train to link ot the feed. I would really love a copy.

    • johnf said:

      I think I have sent this to you. Let me know if you haven’t got it yet.


  17. Henke said:

    Hi John, I would love to have a copy. Trying to cut gears im my home shop and i think it would help to have Hobnail.


  18. Erasmo said:

    I would like a copy of the Hobnail spreadsheet please

  19. Elliot Hirst said:

    Hi John, Just catching up! Please may I have a copy? Regards Elliot

    • johnf said:

      sorry about the delay
      sending to you now

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