Methods of making single or multi tooth wheel cutters

Discussion in 'Horological Tools' started by Raynerd, Jul 5, 2018.

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  1. Raynerd

    Raynerd Registered User

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    Evening,
    As I am now finding more time again to peruse my hobby in clock making after a short spell away, I am again in the position and dilemma of purchasing or making my own wheel cutters!

    I attempted to make my own wheel cutter many years ago and with very limited success! I even went to the extremes of making a eureka tool for back relief - a massive waste of time as the complexities of the device itself caused issues with the profiles.



    I’ve tried multi tooth cutters with off center cutting and I’ve tried single point cutters. I’ve tried the profile freehand and I’ve tried using buttons. I’ve never really been happy with the results.

    Do any of you successfully cut your own wheel cutters and if so, what method do you use? If I can’t find success in this years attempts I will be resigning to buying Thornton cutters for ever more! Sadly, I can’t afford that!!

    I look forward to your replies.

    Chris
     
  2. doc_fields

    doc_fields Registered User

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    Chris;
    Glad to see you back after a long absence!
    I'm getting ready to start a project of making my own gear cutters. I really like what I saw on this website, and want to share this with you. Maybe you've already seen it, but thought I'd give it a toss to you to look at!..................................doc

    Making Multi-Point Gear Cutters

    BTW: Glad you got yourself a Cowell's!
     
  3. gmorse

    gmorse Registered User
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    Hi Chris,

    If you haven't come across this site, it's well worth a look.

    Regards,

    Graham
     
  4. Jerry Kieffer

    Jerry Kieffer Registered User
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    Horological Wheel and piñon cutting is often made far more complicated that it actually is and often misunderstood.

    In industry you produce wheels, gears and pinions that function with each other in an efficient manner per industry standards using standard readily available tooth forms and sizes. The most efficient cutter will have several leaves precision ground so that each carries part of the load. In addition, when each carries its own load, this increases longevity while cutting down on critical setup times greatly reducing cost.

    However in Horology, in real life, there are really no size or tooth form standards. Thus, while wheels and pinions cut with commercial cutters may or may not function properly, their tooth form rarely matches originals typically standing out like a sore thumb.

    Again, if you are a small shop where your work is replacing one off duplicates for repair, your most efficient method will be to produce a quick very accurate cutter to reproduce the tooth form in front of you.
    Under these conditions multi leaf cutters are just not practical. First, they require far to much time to construct. Next, even if you have the expensive grinding equipment to make use of all of the leaves on the cutter, setup and grinding time is again very time consuming.

    My personal solution to all of this is as follows and is covered in the NAWCC workshop WS-119

    (1) The tooth form radiuses of a wheel or pinion are measured and a standard Endmill is selected to duplicate those radiuses.

    (2) Carbon (Unhardened) machinable square stock is placed in a vise in a small Milling machine. Only five very basic cuts are required to machine a single point cutter with only two being critical. The results can be seen in the first photo. Personally, I can machine these in about 10 minutes after many years of doing so, but students report that after a few, it only takes about 20-30 minutes.

    (3) After machining, The cutters are hardened and tempered and sharpened. Sharpening is done on a oil stone per the second photo to razor sharp in only a minute or two.

    In class, After students have made their cutters and cut duplicate tooth forms, fit and finish is compared to commercial cutter tooth forms from earlier demonstration cuts. In most cases, the finish exceeds that of the commercial cutters. One reason for this is that the cutter is designed so it can be stoned razor sharp before each use in about a minute or two. This cutter meets criteria for a small repair shop that requires ease/short time construction,performance and duplication of tooth form. In addition, the shape/design of the cutter allows it to be used in a lathe for cutting duplicate worm gear worms per Third photo as well as decretive shapes etc.

    Jerry Kieffer

    fullsizeoutput_281.jpeg fullsizeoutput_285.jpeg fullsizeoutput_282.jpeg
     
  5. Harry Hopkins

    Harry Hopkins Registered User
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    #5 Harry Hopkins, Jul 6, 2018
    Last edited: Jul 6, 2018
    Chris,
    I wanted to wait until Jerry responded to your request as I knew he would. I am one of his students of the class he mentioned. I want to give you my take on the cutters Jerry described. I have made about a dozen of the cutters for various wheels and I can complete a cutter in less than an hour but a lot of that time is taken to select the correct end mills and gather the rest of the equipment for the job. The actual machining and hardening is done in less than 30 minutes after you have made a few cutters. I have even used them to cut steel pinions and steel wheels although special care is needed when cutting steel. For brass Jerry recommends leaving the cutters glass hard but for steel they need tempered to a straw color. Additionally when cutting steel teeth it is best to hog out some of the material with a slitting saw first then use the cutter mostly for shaping the tooth profile. some of my cutters have been used to make multiple wheels without being necessary to re-sharpen.

    To see some of the wheels I have cut look here: Clock Build Pg.1

    To see a brief description of how the cutter is made look here: Telechron Setting Gear Pg. 1

    One caveat I want to add is that I have no experience with commercial cutters or any other homemade cutter so I can't give any sort of comparison to finish or ease of use other than the wheels I have cut have a finish as good as clock wheels I have duplicated.
     
  6. DeweyC

    DeweyC Registered User
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    I can highly recommend Jerry's method for making cutters. I showed it to the instructors of micromachining while in Switzerland and they just smiled.

    They loved the ingenuity and the simplicity.

    It is the main reason I bought a new Sherline mill which I now use for a number of jobs.
     
  7. Raynerd

    Raynerd Registered User

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    That is fantastic. I am in the U.K. so no way of attending workshops. Is there any way of purchasing any more details for this method. I think I understand the concept but I would appreciate more specifics. Especially about how to chose the suitable end mill. My understanding is that it was impossible to generate a cycloidal form from using a radius of an end mill? Or is the likeness so similar that the true cyloidal form is not generated but just ignored? I do understand everything you say about industry and perfection in multitooth wheels. I am just someone cutting one off wheels, wanting to build clocks that work and so if this method works, I would certainly go with it!!

    Could you provide a little more information about the end mill selection nd calculation involved. For example if you wanted a 0.7 mod wheel cutter, what end mill should be used?
     
  8. James Foster

    James Foster Registered User
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    Raynerd

    I believe you will find this link valuable.

    Jim
     
  9. Jerry Kieffer

    Jerry Kieffer Registered User
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    Chris

    Your actually quite close as I have had students as far as from Hong Kong

    I try not to discuss cutting teeth if possible, as there are a billion opinions. I would rather demonstrate methods for all to evaluate.

    There are many manufacturers of commercial cutters that manufacture cutters in matching sets for both pinion and wheels/gears. Each has their own opinion on tooth form for each given size since the majority of the tooth form has no purpose other than cleanly engaging and disengaging without touching anything to reduce friction and heat.

    The method that I use when commercial cutter tooth forms are needed that I do not have was inspired in part by the cutter set (and others I own) shown in the two attached photo`s. The instructions suggest that pinions and wheels be machined in sets for maximum efficiency of course by their cutters with supporting calculations. For reproducing an existing wheel or pinion, they suggest no calculation, but to simply comparing cutters to the existing wheel until the closest match is found. Unfortunately, I rarely find the fit and tooth form I desire, thus I had to figure out a simple quick cheap system to make my own.
    Upon close inspection of the cutters, to my surprise, I found I could gage pin the radius of each cutter to an available Endmill.
    The system of using the endmills is covered in the link provided by Jim under " Cutting Train Wheels". Dave, the person who wrote this is a very articulate accomplished person who explains the system in text as covered/demonstrated in class far better than I could.

    Many thanks to Harry, Dewey and Jim for the kind words.

    Jerry Kieffer

    fullsizeoutput_287.jpeg fullsizeoutput_288.jpeg
     
  10. Raynerd

    Raynerd Registered User

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    Hi Jerry, sorry, is this a distant learning course?

    I will read the documents and then probably come back on here with more questions! Thanks everyone and James for the links!
    Chris
     
  11. Raynerd

    Raynerd Registered User

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    After reading the first time articles and admittedly only having an hour or so to look at them, one thing strikes me. They are written as to form a replacement wheel and therefore using pins to identify the radius of the known wheel tooth form.

    Maybe I am not thinking hard enough, but what about if you are making a clock from scratch and therefore have no cut wheel to match the tooth form with. So for example, if I am wanting to make a 0.8mod wheel cutter, is there a way of calculating the required end mill without having an example of a 0.8mod wheel to match the radius with?

    Fantastic article. I WILL be dedicating the remainder of this year and as long as it takes me, to learning how to accurately cut these single point cutters. If this is a distance learning course I would definately like to register but I fear it is not and with a wife and two small children, there is no way I will be able to fly to America for this!

    I look forward to your answers regarding cutting known module cutters without a current wheel and also more information on the course!

    Regards

    Chris
     
  12. Jerry Kieffer

    Jerry Kieffer Registered User
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    Chris
    The NAWCC School is in Columbia, Pennsylvania USA.
    I did not expect you would come, just a little Humor.

    You are correct in that the system was designed to duplicate tooth forms and sizes for duplicate wheels and pinions for repair purposes and not specific sized cutters.

    If you are building a movement from bar stock, you can utilize proven tooth form measurements from anther movement or junk movement. While slightly less convenient, far less expensive than purchasing commercial cutters. On the other hand, with proper design, you may only need to purchase one pinion cutter and one wheel cutter.

    Jerry Kieffer
     
  13. sharukh

    sharukh Registered User
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    Jerry,

    Could you provide a link to where I can buy quality end mills in sizes that may be needed for using this method ? I already have a Sherline mill.

    Sharukh
     
  14. sharukh

    sharukh Registered User
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    Chris,

    The book "The clock and watch makers guide to gear making" by Robert D. Porter shows you the calculations.

    https://www.amazon.com/Clock-Watch-Makers-Guide-Making/dp/B002HZTXC2


    And then there are videos on Youtube about making these.

    Here's one




    Below is a 4 part series going into more detail.









    regards,

    Sharukh
     
    Jim DuBois likes this.
  15. Raynerd

    Raynerd Registered User

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    Sharukah - thanks for the links but think I’m going to go down Jerry’s route. I’ve been too long failing at multi tooth cutters!!


    Jerry, thanks for your time replying. Perhaps my option is to to draw and scale up a tooth form based on the module, print it and then use the same method! Means I’ll have to get my head around drawing cyloidal form but it seems like an option.

    Chris
     
  16. Jerry Kieffer

    Jerry Kieffer Registered User
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    Chris
    As mentioned it is an option, however the accuracy involved my be a concern, while a inexpensive junk movement is a proven system.

    Jerry Kieffer
     
  17. Raynerd

    Raynerd Registered User

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    Hi Jerry

    I’m not entirely sure how that would work. So I know that the clock plans call for 0.7M Wheel. How do I physically get a clock wheel that is definately 0.7M. I have lots of clock wheels kicking around, I suppose my point is, how do I find a junk movement knowing it will be the module I’m after? I hope you understand my point.

    Chris
     
  18. gmorse

    gmorse Registered User
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    Hi Chris,

    If you know the required module, you can check an unknown wheel by measuring the Pitch Diameter, (in mm), and divide it by the number of teeth to arrive at its module. To arrive at the PD, you could use the formula on page 2 of David Morrow's document on wheel cutting linked to earlier in post #8 of this thread, (with appropriate conversions to metric):

    ii. Or stated the W.R. Smith way “OD = M inches (N+2.76), where M inches is
    the module in inches, N is the number of teeth and…the 2.76 factor is the number of imaginary teeth required to increase the size from the pitch diameter to the outside diameter of the wheel blank."


    Regards,

    Graham
     
  19. Raynerd

    Raynerd Registered User

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    Hi Graham, thank you for your time to reply and apologise, I don`t think I correctly explained what I mean. I am trying to say how would I logistically find suitable wheels in the correct modules that a scrappers and cheap. So sticking with the 0.7mod again, looking on ebay or even here, it will be very difficult to find a clock wheel of 0.7mod as people would have to measure for me and for junker movements, sellers are just not going to do this. Once again, I`m not being pessimistic I`m just trying to be realistic. For me now to start searching for a cheap 0.7mod cut wheel, it may be easier to buy a PPThornton Cutter - but that isn`t the point! I want a reliable way of making my own wheel cutters and Jerry`s method seems just the job! I just need to try and figure out this hurdle of finding my comparative tooth form!


    Without getting too bogged down in this comment as I`m sure it would be incredibly difficult to do, but there surely must be a calculation that depicts the shape of the tooth form from the module and then finds its comparative radius end mill!
     
  20. Jerry Kieffer

    Jerry Kieffer Registered User
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    Chris
    To make a long story short, I designed the system because existing Horological tooth forms rarely calculate out to current modules offered by cutter manufacturers. So I doubt you will find what you are looking for. As such, I would suggest purchasing a junk movement or other devise with about the same physical size as what you would like to construct and use those tooth forms. Or of course a repair person may lend you whatever you need once they learn you are cutting wheels.

    Jerry Kieffer
     
  21. Harry Hopkins

    Harry Hopkins Registered User
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    Chris,
    I am not where I can look at my reference material at this time but I faced the same dilemma as you as I wanted to build a movement from bar stock and had no wheels to use as a model. I believe the instructions for making my movement called for a module of .82. I used all the info from Jerry plus reading J.M.Wild's "Clock Wheel and Pinion Cutting" found here. In Wild's book there are several useful tables and all the calculations necessary for you to create Jerry's cutter to a specific module. It did take me a few readings to fully understand it but all the info is there. The calculations from GMorse above look familiar and I suspect that is one of the formulas in Wild's book as well. I made several notations in my book and when I return home in a couple of days I will review it and if you have more specific questions maybe I can help.
     
  22. John MacArthur

    John MacArthur Registered User
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    Wild has Addendum R = 1.93 x M, or for M 0.7, addendum R = 1.35 mm or .053 in. Since finding an end mill of this diameter will be hard, some will drill two holes the appropriate distance apart in the square or flat stock, and file to the tangents of these holes. Daniels suggests drilling slightly undersize, and opening up from the back with a taper reamer, for clearance. Number drills will get you close. Other methods (Perkins, Goodrich) use a round cutter of the right diameter on end, to form the radius of the cutter you are making. This is done in a lathe, and makes a round blank, which you then file or grind down to half the diameter. I have used all of these, with varying degrees of success.

    When my office computer comes back from repair, I will post some pics, which will help. I think Goodrich is in the public domain, and so I could scan some of his drawings, too.

    Edit: bitsbits.com has many small carbide endmills

    Good luck,
    Johnny
     
  23. Raynerd

    Raynerd Registered User

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    I understand Jerry. Thank you for the design and it does seem to me that I will be able to achieve what I am after and use your method of cutting. We will see!


    Harry, I do own this book and pulled it out this evening. However, after a day at work I am too tired to fully appreciate the equations and will look properly tomorrow.

    What is interesting is that I also pulled out George Daniels books which has some excellent information in it. He also seems to show how to calculate the exact radius we are looking for and includes formula and references to British Standard 978 Part 2 which I know is what PP Thornton use for their dimensions. When I am less blurry eyed tomorrow, I’ll do some calculations based on these different equations and books and see how comparative they are.....and possible see if you are interested in reviewing them to check for errors!

    John, whilst I haven’t quoted your post directly, thank you for those equations and I will do some trial calculations tomorrow.

    Speak to you all tomorrow and thanks for all your help. I very much appreciate it.
     
  24. John MacArthur

    John MacArthur Registered User
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    Chris - Here is a diagram of teeth generated by computer to epicycloidal form, by elliptical forming shown below, and by radius form. As you can see, the elliptical comes the closest that we can to approximating the theoretical perfect form. The way I did it, years ago was using the "offset" method, after Goodrich, Perkins, and others. This is does the same thing that Jerry's method does when he tilts the blank and mills the cutter with relief. I really don't remember how I came up with the appropriate angle for the cylinders that make the ellipse, but I imagine it is from Goodrich, as Perkins hadn't written his book yet. I also don't think it is ultra critical, as high numbered gears and pinions depend as much on consistency and finish as pure form.

    3.1 teeth forms.jpg 1 elliptical cutters and holder.jpg 2 elliptical cutter in position.jpg 3 elliptical showing relief.jpg

    Also shown are several varieties of similar cutters, mostly hand formed, and the 1890 Sebastian lathe with various contraptions that I made to cut gears and pinions with. This was "doing the best I could with what I had". The clock I made with that setup (1985) is running fine in my hall, keeping time within a couple of seconds a week, after more than a billion ticks.

    I feel your concern, having been down this path. Now I use Thornton cutters and comparatively modern machinery.
    Johnny
    4 cutters.jpg 5 1890 Sebastian lathe.jpg 6 old gear cutting.jpg
     
  25. Raynerd

    Raynerd Registered User

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    Thank you. In your picture it shows the calculation as 0.193xMod = radius. Can you please confirm that is what you used and not 1.93.

    I am having some frustrations in my calculations so this difference has also not helped! I am just about to post a longer message with regards to this.....
     
  26. Raynerd

    Raynerd Registered User

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    I now have quite a bit of confusion and would appreciate your help. Just to reiterate my intent, I would like to use this method to cut my own single point cutters and therefore need to calculate the addendum radius to find a suitable diameter endmill.

    I have previously purchased both Daniels Watchmaking and also J Malcolm Wild – Wheel and pinion cutting in horology.

    After now hours of reading and reading, I am confused. It seems to get quite technical but I am confident I have my head around it and yet different books are giving me different radius for the tooth tip. If you have either of these books I would appreciate you checking I am not making an obvious error. If you don`t, then I`d appreciate your thoughts and checking my calculations.


    Example: A wheel of 0.2Mod with 36 teeth drives a 12 leaf pinion. What is the radius of the addendum on the 36 tooth wheel.

    1. J.Wild –Wheel and Pinion Cutting in Horology, p310: States that Addendum Radius = 1.93 x Mod. Therefore in this example that would be 1.93 x 0.2 = 0.386mm and I would be looking to use a 0.772mm diameter end mill.



    2. This can be confirmed in the same book, Appendix VI in which Wild states common measurements for tooth form. He clearly states that 0.2Mod will have a radius of 0.39mm, clearly the 0.386mm I calculated, rounded up and therefore a 0.78mm dia end mill.

    1. George Daniels – Watchmaking p108, Fig 202 (incorrectly labelled and an error in the book, it should be 203). Titled: Derivation of a common addendum radius: Radius = (pi x Mod)/2. Therefore (pi*0.2 )/2 = 0.3142mm radius and therefore a 0.628mm endmill.



    2. George Daniels – Watchmaking p109 Fig 204, then explains the concept of derivation of a variable addendum. He explains that every wheel tooth radius should really be unique based on the ratio of wheel to pinion and the number of teeth on the pinion. He explains that this is calculated from the table in British Standard 978 Part 2 and the radius will equal the module x R factor in the table. Is this example, the ratio is 3:1 and BS978 Part 2 (quoted in both books!) shows a Rf value of 2.396. Therefore 2.396 x 0.2 = 0.4792mm and would then require an endmill of 0.958mm diameter!


    So the 4 different methods give me end mills of 0.77, 0.78, 0.63 and 0.95mm!


    The two big issues are: Why does Daniels common addendum calculation not match, when must be a common addendum calculation in Wilding`s book. Secondly, I would fully expect that a true variable addendum radius would be obviously different to the common/averaged addendum radius but I think the difference between 0.7mm and 0.95mm diameter is quite large?


    I know it is quite a lot to check through an take in but I am really struggling and would appreciate your thoughts.


    Chris
     
  27. Jim DuBois

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    To your point of possible frustration, Jerry Kieffer says it very well, earlier in this thread, "However in Horology, in real life, there are really no size or tooth form standards. Thus, while wheels and pinions cut with commercial cutters may or may not function properly, their tooth form rarely matches originals typically standing out like a sore thumb."

    While the current so-called standards for epicycloidal cutters were spelled out in British Horological circles more than 100 years ago IIRC, your results using these formulas shows the various ways to define the tooth profiles are not in agreement. Unless you are attempting to make an absolutely precise clock, as near perfect as experts might agree (novel concept I fear) then something close tooth profile wise is good enough. I know of more than one clock that runs within a second a week, or even better, using involute (gads!) wheels and pinions. And, if we look at the works of some of the greatest clockmakers (Harrison anybody?), we can see from their remaining work today they did not use close profiles as defined by cycloidal form to British Standard 978 part 2, or Swiss Standard NHS 56702 or Swiss Standard NHS 56704. And we have perhaps 400 years of decent running clocks where teeth were frequently profiled by eye with a file.

    There is more than a modest risk of becoming mired in the minutia of tooth profiles......
     
  28. Jerry Kieffer

    Jerry Kieffer Registered User
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    #28 Jerry Kieffer, Jul 12, 2018
    Last edited: Jul 12, 2018

    Chris

    This is one the very reasons that the endmill system that I offer for consideration exists.

    It only has one purpose and that is to DUPLICATE tooth forms that have PROVEN that they will function over the long haul.

    Over the years, when it comes to gear cutting calculations, I have learned to DISREGARD ALL OPINIONS AND CHARTS, UNLESS they are provided by Manufacturers of cutters. In this case, the manufacturers, have developed cutters that produce functional Wheels/Gears/Pinions or they would not be in business. The cutter set I posted is a superb example in that none of the cutter profiles will match any of your calculations or exactly to any other manufacturer.

    To fully understand how properly depthed teeth function with each other, YOU MUST EXAMINE THEM WHILE THEY FUNCTION under optics in slow motion. You will find that tooth contact with each other IS ONLY confined to a VERY TINY area of only a few thousands of an inch. The rest of the profile is for clearance and IS NOT critical as long as the tooth forms clear each other, thus each manufacturers clearance profile can be different without effecting operation.

    To successfully use the system that I have offered for consideration, you must disregard all charts and calculations and understand that it ONLY DUPLICTES AN EXISTING TOOTH FORM and is NOT designed to produce a set of cutters to any particular industry standard. Your current Approach if you wish to use this system, will likely not work unless copying a commercial cutter.

    The MAIN REASON this system exists is to DUPLICATE TOOTH FORMS for Quality restoration (both visual and function) of movements and instruments that is not taken into consideration by any Publication or Manufacturer that I am aware of.

    To clear up the endmill size issue.

    The Wheel and Pinion class at the NAWCC School is a two day class and it is not practical to cover all of the fine details on a forum like this.

    Endmills are sold in Decimals, Fractions and MM. It is very likely you find the desired endmill required within a couple of thousands that will work without any issue what so ever ever.
    However if perfection is required/desired, it is no issue. When machining the cutter, I suggest that the cutter blank be mounted in the Milling machine at about a 15 degree angle for cutter clearance when cutting teeth. By increasing or decreasing this angle slightly you can change the Endmill cutting radius (increase or decrease) slightly thus achieving perfection if so desired even though seldom required.

    Jerry Kieffer
     
  29. John MacArthur

    John MacArthur Registered User
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    Chris == Sorry, My bad -- of course the formula is 1.93, and not .193. Transposition error..... but heed Jim and Jerry - a clock that you make with anything close to the correct form teeth will run remarkably well. I get that you want to do it "right"; I too obsessed about this many years ago. But my first pinions were cut with a slotting saw, then faceted at the square top corners with the same saw, and then hand finished with a file. Took quite a while, but worked out very well. The flycutter for the gear teeth that you see above was hand formed to my best guess. Wild and Daniels are/were both *really* good at what they do, but some sort of average ought to work quite well. Cut away and see what happens.
    Johnny
     
  30. John MacArthur

    John MacArthur Registered User
    NAWCC Member

    Chris - I just checked the radius of a tooth face on a wheel (0.6 m) that I just cut with Thornton cutters. I used a sharp gage pin .092" d. (2 x .046, the correct r per Wild) and it is as close to the same form as I could see under 20x microscope. The tooth tips are possibly a slightly diminishing radius, probably for clearance if one were to be engaging a lower number pinion. I would imagine that if you use that formula, 1.93 x M, you'll be fine. As Jerry says, you may only get within a couple of thou on end mill size; I'd probably err on the small side. Large would make the tooth addendum longer, sharper, and more likely to interfere with pinion leaves. Smaller will make a slightly rounder tooth tip, probably not in the area of engagement.
    Johnny
     
  31. Raynerd

    Raynerd Registered User

    Apr 11, 2004
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    Johnny,
    Sorry for the very slow reply! I appreciate your efforts and after further reading of Wildings books, he seems to suggest that this calculation is in line with P P Thornton cutters. Your very helpful practical measurement confirms that! Based on this, I’ll give it a bash and see what happens! Thank you

    Chris
     
  32. John MacArthur

    John MacArthur Registered User
    NAWCC Member

    Chris -- Good luck, and let us know how it turns out.
    Johnny
     

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