Free hobbing - a rogue method for spur gears - Page 2
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  1. #21
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    From the generous remarks at the top it appears I should should restyle myself


    Cock Robin[/QUOTE]

    What's that up my arse Batman?

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  3. #22
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    Quote Originally Posted by digger doug View Post
    I had no problem-o with my Dodge 2500, you've got to match the speeds.
    The problem isn't matching the speeds, I've tried it. The problem is the design of the trans. Full synchros, Japanese trans won't allow it. Trust me, I've tried. No prob with the New Process boxes which your Dodge most likely has (yeah I'm kinda envious, they are nice gearboxes). And of course it's no problem on the heavy truck boxes, no synchros at all in those.

  4. #23
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    Hi again Robint:
    What is your objective here?

    Are you hoping to make gears for a project?
    Are you hoping to play with the method to see where it takes you?
    Are you hoping to find the best way to make gears of adequate quality in your shop with your equipment?

    Be aware of two things:
    1) If you want to hob gears, you will greatly improve what you get by actively driving the workpiece in relation to the hob...this point is not up for debate.
    There are a gazillion ways to do this in the modern era; an encoder on the hob spindle and a stepper driven rotary table is a common way for hobbyists to do this.
    Used to be you had to rig a physical gear train between them...that was a cumbersome and painful way to get there but it does work as you can readily see from countless old hobbers out there in used machinery land.
    Nowadays you don't have to, making your life much much simpler if you want to make a hobbing setup that actually works and can turn out a respectable gear.

    2) The hob is at the heart of your success always, always always!
    I can't overstate this enough...trying to do this with an Acme tap (or any other kind) is utterly doomed to fail for anything even remotely like a proper involute tooth form.
    You'll notice, the guy in the video you linked used a commercial hob, and he managed to get something out of it that looks reasonably like a gear.
    Part of what you must do is ensure the hob does not run out at all...much of the failure hobbyists often encounter comes from a crappy arbor, supported only on one end, in a sloppy Asian import mill with shitty bearings.
    The result is not encouraging...it is worthwhile to do better, and it's not that hard to do.

    As a last point...this forum was originally set up for professional machinists to brainstorm problems of the kind that professional machinists typically encounter as the forum guidelines point out.
    There are a gazillion hobbyist forums out there that will run with this kind of topic enthusiastically, but this is not that place, as you're finding out.

    Don't be surprised by your unenthusiastic reception here...fighting back against the understandable snark will never get you anywhere but mining the few posts that actually try to point you in the right direction just might help you.
    A pissy attitude however, will only make it worse, and you'll get nothing useful from me or anyone else.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  6. #24
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    A few years back, I bought a new Hellcat with the 6 speed. I took it over to my friend's to show him...he is a professional truck driver and drives a stick every day. We went out for a drive, I thought nothing of letting him drive....until he started driving. First, he stalled the car 3 times before we got rolling. That's OK...the car has a fairly abrupt engagement and tall first gear. Then, although he knew it had 6 gears, he would run up each gear to about 4000RPM and hold it there a while until he decided to upshift. Since we never went much over 65MPH, that meant he made it into 3rd gear and there buzzed down the highway at 4000RPM. Umm.....

    As a professional driver, he was also wicked-anal about checking all the mirrors twice before changing lanes, and using the turn signal. That sounds good, but when you know there are no other vehicles within a mile of you, and a lane change takes 30 seconds, it begins to grate the nerves. The final straw was when he would toot the horn 3 taps before backing up. Never again.

  7. #25
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    Diesel trucks have a governor, and even though it's not so much a load holding governor, it definitely
    is easier to let the clutch out with a diesel.

  8. #26
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    Quote Originally Posted by Robint View Post
    I have always conducted myself properly on this Forum and have never disrespected members or the code of conduct but I reserve the right to correct defamatory remarks made against me who, I said at the outset, would not like the topic of this thread. Why dont they just move on , its not for them
    "Always" ??? for qty (2) days ?

    Sit back, push the keyboard away from you, and READ THE ARCHIVES FIRST.

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  10. #27
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    Hi Robint:
    Here you go:

    Machinery Discussion Guidelines

    Off Topic Post Guidelines

    Now I don't much care if you violate the rules...I'm not a rule follower anyway, and it's not my business to be your mother.
    But given the guidelines are readily accessible and are clearly stated, are you surprised by this outcome?

    Not only that, the points I've made specifically about key aspects of your topic don't even seem to be of much interest to you...certainly not enough interest to spark a discussion or even a debate.
    That's not encouraging...I don't get the impression that you're willing to even entertain a conversation about why this method suffers from the shortcomings it does.

    Nobody but a hobby guy is much interested in adoringly following the "Free Hobbing" religion...I could tell you why in some detail, but if you don't even care to listen or discuss it...what's the point?

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  12. #28
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    The only reason free hobbing works at all in the real world is that there is no axial movement of the cutting tool. The process works for finish cutting a gashed wormwheel as the only feed motion is radial, and the indexing motion is provided by the cutting tool "meshing" with the previously gashed blank. Yea, you can cut small worms in an ungashed blank using a tap as a cutting tool- and it works due to the low cutting forces involved- high precision- no, but it works.

    With regard to using the same method to cut a spur gear, yea, you might get spaces cut between the "teeth", but the axial feed necessary to cut a tooth space all the way across the blank will always be problematic and produce a drunken lead- no way around that. There is a reason that hobbing machines gear the work piece to the cutter spindle in a very definite relationship. Probably nuf said on the subject.

  13. #29
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    Thanks Dan:
    Yes, I've free hobbed small worm wheels for adjustment mechanisms on home made tools, and it does work well in that application.
    Here's a picture of part of a mechanism for machining custom dental implant abutments...I needed to be able to match the angle of an implant to the emerging fake tooth, and a worm adjustment was the easiest and best way to get there.
    The worm is about 1/2" OD and was made with a 10:24 tap.
    It was gashed by making a simple fixture to run a tap into a hardened threaded bushing that was positioned next to the blank which was mounted to a rotary table to allow it to be indexed for each tooth.
    The gashes were run one after another by indexing the table, running the tap through the bushing, withdrawing the tap, indexing etc etc, and then the worm was finished by free hobbing it.

    For this project I didn't need an accurate worm...I was aligning a dental implant abutment blank by eye to a reference post with a light shining behind it and what I needed was fine incremental adjustment without having to bang things around to shift them.
    In this application it worked very well, but the gashing was a crucial first step, and the whole process took a long time to complete.
    For this fixture it was worth it, but it is hopelessly inefficient unless your need is quite specific as mine was.

    So I do have experience with the method, but I fully concur with you that for making spur gears, it's intrinsically pretty hopeless unless your needs are pretty crude.

    Cheers

    Marcus
    www.implant-mechanix.com
    www.vancouverwireedm.com
    Attached Thumbnails Attached Thumbnails dscn5410.jpg  

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  15. #30
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    Hi again Robint:
    You are aware, I hope, that Dan from Oakland whose comment you are disparaging, is a professional gear maker with a mountain of experience.
    Do you think perhaps his opinion is untrustworthy?
    Do you feel that inspection with an optimistic eye under a loupe is equivalent to proper gear measuring equipment, and that you know better than him because you've SEEN it on Youtube.

    If so, I want to have some of what you're smoking.

    Now that this thread has completely gone down the shitter, it's getting hard to continue to participate.
    I feel like a kid picking on a scab...it hurts and I know it's gonna bleed, but I'm having a hard time stopping myself.
    So I think it should probably end...my last post with the picture was partly a last effort to bring it back from the brink, but I think the train's well and truly over the cliff.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  17. #31
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    Quote Originally Posted by Robint View Post
    Now this is an example of the kind of armchair speculation that I have to fight against
    Not this was funny … Umm, Dan has been cutting teeth commercially for a good forty years. Making gears and selling them. He has products. You've got shit.

    When you see your rig actually produce a passable spur toothed wheels in front of your very eyes its hard to believe at first, it happens so quickly
    Unlike a Liebherr L900 that takes a while cutting 2 DP teeth on a 30" blank … altho a little 6-10 is pretty quick on quarter-inch diameter stainless spline shafts. D from O does both, on a daily basis. Unlike some people ...

    If you ever get even a vague idea of what you are talking about, maybe come back and give a lecture. Until then, go teach your grandma to suck eggs.

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    Hard fuckin crowd to play to.

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  21. #33
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    Quote Originally Posted by Robint View Post

    ,,,,,,,,,,,,,,,,,,,,,

    These are AMATEUR toothed wheels

    .............................................
    And a forum for professionals.................. Try the Home shop machinist, or that sort of forum.

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    Quote Originally Posted by Robint View Post
    What is it about you guys I try and shoot straight

    talk about two great nations (and of course our former colonials bless em they share the same quirk as we brits - apologies to the French) divided by a common language

    You are missing the whole point here

    What I said, and I bow to the mountain mans experience as a professional gear maker - thats not in dispute at all, people who have never tried out the method make disparaging remarks about it

    Look at the Vid

    and no visual inspection is no substitute for very expensive professional gear testers

    These are AMATEUR toothed wheels

    put them in a rig for light load and they work

    Why are you still denying the evidence?
    Nobody is denying the evidence that you can make a low-grade gear spin against another low-grade gear with this method. Cheers and celebration for you, go pat yourself on the back. Get real ambitious and put some magnets on the back so you can stick it to your fridge and let your kid spin 'em round and round while you cook dinner.

    Thing is, nobody here cares.

    I admit that I'm a wannabe machinist at best, more than 80% of the time I walk up to my machines it's a hobby job, the rest of the time is a (generally simple) support fixture or assembly to help me accomplish my work in my engineering role. But when I log on here, it's to learn from some highly skilled and experienced individuals, or lend my own knowledge in the rubber industry to those who have questions. I don't bother everyone here with pictures of the stuff I make myself and expect all these crusty old bastards to fawn over it, this isn't instagram.

    There's a fundamental problem with the reason you started this thread. What problem are you attempting to solve? If you don't have a good answer to that question, it's probably not a good thread for this forum.

    You can shoot as straight as you want, but if you aren't aiming anywhere near the target you'll never hit it.

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  25. #35
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    Robin:
    You wrote:
    "people who have never tried out the method make disparaging remarks about it"

    I HAVE tried out the method...I KNOW it works for certain applications.
    I KNOW it doesn't work for others.

    It makes decent worm wheels.
    It makes shitty spur gears...if you think that's a disparaging remark, then by all means free hob away, enjoy your delusion and gear with pride and enjoy your gears such as they will be.
    If you pay attention to the proper details you can make better ones...if you don't you can't.
    I can't be bothered anymore to tell you what those details are because we can't really have a discussion with you anyway, even if we still wanted to.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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  27. #36
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    Quote Originally Posted by BoxcarPete View Post
    Nobody is denying the evidence that you can make a low-grade gear spin against another low-grade gear with this method. Cheers and celebration for you, go pat yourself on the back. Get real ambitious and put some magnets on the back so you can stick it to your fridge and let your kid spin 'em round and round while you cook dinner.

    Thing is, nobody here cares.

    I admit that I'm a wannabe machinist at best, more than 80% of the time I walk up to my machines it's a hobby job, the rest of the time is a (generally simple) support fixture or assembly to help me accomplish my work in my engineering role. But when I log on here, it's to learn from some highly skilled and experienced individuals, or lend my own knowledge in the rubber industry to those who have questions. I don't bother everyone here with pictures of the stuff I make myself and expect all these crusty old bastards to fawn over it, this isn't instagram.

    There's a fundamental problem with the reason you started this thread. What problem are you attempting to solve? If you don't have a good answer to that question, it's probably not a good thread for this forum.

    You can shoot as straight as you want, but if you aren't aiming anywhere near the target you'll never hit it.
    I smell a rat:
    Not happy with new Pressbrake

    From the linked:
    "This is my last comment on this thread. I want to thank all involved. The real purpose can now be revealed. I am working with a college student who is studying social media and how it has changed people's attitudes. I am not normally as arrogant and rude as I appeared in some of the posts. This was all done to test reactions and observations and test thought processes. We wanted to see how we could change opinions and views and it turns out people always want to see an underdog come out ahead. Another underlying thing that the student is studying is the current atmosphere regarding sexual abuse and the allegations and how to defend against claims with no real evidence on either side. Again thank you all for helping out."

  28. #37
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    Quote Originally Posted by JST View Post
    And a forum for professionals.................. Try the Home shop machinist, or that sort of forum.
    He already did... that's why we sent him over here. Because we're all just "armchair machinists" I guess.

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    Go away hobby hobber

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  32. #40
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    (Sigh) A saying we have in mining, he's a legend in his own mine. I've met at least a dozen just like the OP. Knows everything and can't be told anything. They always use condescending wording to talk down to everyone else because to them anyone and everyone else is beneath there own highly inflated ego and completely false opinion of themselves. In other words they don't know enough to understand how little they really know, and that built in attitude will never change. I read that HSM thread over the last few days and shook my head at every post he made. This brain dead fool has a true death wish to try the same here. Even though I'm only and always will be at the hobby level, the total lack of respect by far too many of those same hobbyist's here for actual professionals is literally cringe worthy. If it were up to me I'd instantly ban this prick because he's going to go out of his way to piss as many off as he can until he leaves anyway. Until then I'll watch him get destroyed, it should be truly epic and something to fondly remember for many years to come even for this forum.

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