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My first spur gear

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  • outlawspeeder
    replied
    That was one hell of a set up and one I have not tried. (now added to my list of hey try this trick) As far as cutting gears vs rollers, if it works for the propose I would call it a gear. If it lasts, I would call it a good gear.

    The life of a body sander it is exposed to more grit than the cars it will repair. If this low cost fix save a tool from NAPA, great! What might help keep this you gear rolling (pun intended) try blowing out the sander when you clean the car after sanding? Letting that crap get into the gears … well you know the rest.

    Great job making the gear.

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  • flathead4
    replied
    To make matters worse, my setup meant that the tool steel had to be less than an inch long so holding the tool steel while grinding was an issue.
    Could you have left the tool steel bit full length for grinding the cutter end and then cut it to less than an inch? If not, short bits I usually hold with pliers or vise grips.

    Tom

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  • herbet999
    replied
    Originally posted by rock_breaker View Post
    Very nice work! How did you get the cut to proper depth?
    Thanks... After shaping the cutter, I clamped the original gear and the new blank gear together using the shaft that the gear rides on in the air sander. I then used the original gear to set the depth of the cut.

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  • Paul Alciatore
    replied
    I don't claim to be any kind of expert on gears and I certainly do not have the years of training and experience that Juergenwt has. But I do seem to recall that clock makers in the past have made gears, yes, REAL GEARS, using just a file and a good eye to cut the teeth.

    I have no idea as to how good or bad herbet999's gear actually is and perhaps neither does he. But he made a gear and installed it in his sander and it is working. I say hip, hip, hooray. And if it is not perfect, who is to say that it will not improve with use.

    If it fails, I am sure his next one will be better.

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  • rock_breaker
    replied
    Very nice work! How did you get the cut to proper depth?

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  • uute
    replied
    deleted- eronious statement
    Last edited by uute; 11-27-2012, 12:09 AM.

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  • firbikrhd1
    replied
    Of course it's a gear! Centuries ago gears were made by hand with rasps for wood and later files for metal. If it works it's a success. I think herbert999 did a great job of working with what he had to make his sander work again. If parts aren't available, the sander is just so much scrap metal, unless a gear is made. Having a super accurate one professionally made would cost more than a new sander and it would run against a worn used gear probably ruining it's "super accuracy" is short order. Some guys here, real machinists with high end machines, tons of tooling and lots of both, frown upon us home shop guys who make do with what we have because the result isn't up to NASA standards. Fine, so be it. herbert999 had a problem, accepted the challenge, used ingenuity to over come it with what he had on hand. That sounds a lot like how it was done 100 years ago and demonstrates the same attitude that allowed America and her allies to win WW II. Unfortunately much of that innovative can do attitude is absent today.

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  • Wheels17
    replied
    And while Juergenwt is busy researching, reading, assembling equipment, using hundreds if not thousands of dollars worth of tooling and equipment on his method, herbet999 is back out in the garage, happily using his sander, which is the whole point of the exercise.

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  • michigan doug
    replied
    Well, this got so much better. Juergenwt, I apologize for calling you a jerk. I think everyone, almost, appreciates constructive criticism, we just didn't see any of the constructive part in your first post.

    Your points are well taken as to the risk of using an expedient quick and dirty "gear" in an otherwise good gear train. They won't play well together in the long run. I suspect that the OP's gear train is not pristine, so there is less at risk, and it's not a life or death NASA application.

    If I could make only one improvement in the OP's method, it would be to put the gear blank on one end of a shaft, and a 6" disk on the other end with a carefully laid out tooth spacing interval. One can be surprisingly precise with some patience and a pair of dividers. There are other methods as well that would not involve a rotab.

    If I could make one more improvement, it would be to make a better cutter that more faithfully produces good tooth geometry. And you're right, there is a lot tied up in tooth geometry.

    Finest regards,

    doug

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  • herbet999
    replied
    Originally posted by Juergenwt View Post
    Herbet999 - you did a fine job to keep your sander going. What we have here is a "failure to communicate". Just like somebody may be able to help himself by replacing a bad tire one a bicycle with a water (garden) hose to keep going because he either could not get a new tire or he did not want to spend the money for it. It worked and that is what matters.
    However - that does not make the replacement water hose a bicycle tire.
    Just like nobody in his right mind would put this "Gear" in his Harley, having it produced in the way it was described.
    So, for people having no knowledge of the geometry involved in making a gear - it looks like a gear - therefore it must be gear -
    it all boils down to the question of whether it was made by someone doing the best he could just to help himself - and in many cases that's what it's all about- or was it made professional. I hope your sander works good for a long time.
    For all who would like to know more please Google: Gear tooth geometry or gear tooth cutter geometry.
    This has been an interesting little conversation and exchange - not really a big thing - but something applicable to a number of other posts on this Forum.
    I appreciate your input. As I stated in the original post, this gear was for an air sander. I have no intention of making one for my Harley even if I had a Harley. I think you are correct in pointing out that my method is not going to be sufficient for a lot of applications.

    My interest in machining is more in support of my interest in cars and less a direct interest, although I enjoy machining as a hobby as well.

    The reason for the post was three fold. First to gloat about my accomplishment. Second, to relay my experience in creating what I needed with minimal equipment (I include my lathe as minimal equipment only because it too was hobbled together from bits and pieces I've gotten on the cheap). Third, in hopes to elicit responses on how I could better my results within the confines of the level of equipment I'm using.

    As for my experience, I found that indexing the blank using the old gear worked fairly well and I think is accurate enough for what I was trying to do. I also found that cutting at the slowest speed (125 rpm) worked the best and allowed the cutter to last through all eleven passes. I did use oil, applied from a squeeze bottle, for lubrication. I think the least accurate aspect to my process was the shape of the cutter(s) themselves. As I mentioned, I ground tool steel into a cutter by hand using a basic 6 inch bench grinder. To make matters worse, my setup meant that the tool steel had to be less than an inch long so holding the tool steel while grinding was an issue.
    Last edited by herbet999; 11-26-2012, 10:38 AM.

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  • John Stevenson
    replied
    Originally posted by Juergenwt View Post
    Just like nobody in his right mind would put this "Gear" in his Harley, having it produced in the way it was described.
    .

    Bollocks, it's probably 3 times better than a Harley gear
    Wish it was in the down feed of my POS Bridgy instead of the ones made by Timex.

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  • Juergenwt
    replied
    Herbet999 - you did a fine job to keep your sander going. What we have here is a "failure to communicate". Just like somebody may be able to help himself by replacing a bad tire one a bicycle with a water (garden) hose to keep going because he either could not get a new tire or he did not want to spend the money for it. It worked and that is what matters.
    However - that does not make the replacement water hose a bicycle tire.
    Just like nobody in his right mind would put this "Gear" in his Harley, having it produced in the way it was described.
    So, for people having no knowledge of the geometry involved in making a gear - it looks like a gear - therefore it must be gear -
    it all boils down to the question of whether it was made by someone doing the best he could just to help himself - and in many cases that's what it's all about- or was it made professional. I hope your sander works good for a long time.
    For all who would like to know more please Google: Gear tooth geometry or gear tooth cutter geometry.
    This has been an interesting little conversation and exchange - not really a big thing - but something applicable to a number of other posts on this Forum.
    Last edited by Juergenwt; 11-26-2012, 01:40 AM.

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  • J Tiers
    replied
    You do not need anything super special to copy a gear which you have one of.

    Here is an indexing system that I used several times to make bevel gears. Once with a hand ground cutter used in a shaper, otherwise with a horizontal mill, similar to the lathe method of the OP.

    The screw you see at top of the fixture is to hold the master gear (a change gear from lathe) indexed to position. The whole thing was cobbled from scrap pieces that I had on hand.

    The goodness of the form-cut gear is the goodness of the cutter, which may be commercial as in the picture, or hand ground fly cutter as the OP used (and I have made also). One correctly ground cutter is enough, should not need several, unless you try to do the undercut tooth form, in which case you may need an extra to do that cut.

    The hand ground one was ground to fit the mating identical gear, and might as easily have been used as a fly cutter similar to the OP original method.

    The cutter, no matter the type, must be set radial to the blank, so the cut teeth will be straight. That is same with any gear cutting.

    A similar item to the one pictured might be made horizontal, not at a 45 deg angle, to make spur gears using one gear as a master.

    Last edited by J Tiers; 11-25-2012, 07:21 PM.

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  • herbet999
    replied
    This is what I needed the gear for. My inline sander. Works great. I'll see how long it lasts.



    In the exploded view the gear is part #32. Just about the center of the page

    Last edited by herbet999; 11-25-2012, 01:49 PM.

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  • John Stevenson
    replied
    Originally posted by Juergenwt View Post
    Now for Equipment:You need at minimum a Dividing Head. Depending on the number of teeth you may need a differential Dividing Head.
    You also need a horizontal mill and a gear cutter that represents the diametrical pitch or modul as well as the number of teeth you are cutting.
    You need to be able to measure the pitch dia. To get this you need the formula from the Handbook to get the right dim..
    In this case: Pitch dia = divide the product of number of teeth and outside dia. by the number of teeth + 2.
    You have to find out how to measure your gear.
    Many more things to consider before you even start. You will find all of it in your Machinist Handbook.
    The internet could be a good source. Making a gear that will work is not for someone with limited experience.
    Even if you should have the basic equipment - it would not be a gear to be used at higher speeds (Rpm). Those will have to be heat treated and ground and would require a very special steel.
    Hope this points you in the right direction.
    Here is a very short movie on how to make a gear: http://www.youtube.com/watch?v=VHTXaU7GZC0
    Damn, no wonder I have been going wrong all these years, I obviously don't have the bare minimum, - damn.

    Mind you the You tube video linked to is only using a crap Chinese round column mill drill instead of a horizontal mill and we know how crap they are.

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