Machsupport Forum
Tangent Corner => Tangent Corner => Topic started by: Riddler on March 20, 2010, 11:05:44 PM
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I came across the video below of a guy using a endmill to cut gear teeth into a brass blank. Very cool, but I am looking to do the same thing and I can not find a end mill like the one used in the video. I can find gear tooth milling cutters galore but not end mills with gear tooth profiles. Can any one point me to where I might find them? Or what are they called to search for them.
http://www.youtube.com/user/John5tevenson?aia=true#p/u/7/fps0OR1eF_s
THanks
Scott
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Hi Scott,
You may find this of interest. http://www.patentstorm.us/patents/6591715/description.html
Tweakie.
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That is exactly what I am looking for.
Does any one sell these style of cutters?
Thanks
Scott
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Hi Scott,
I think you are going to have to make your own cutter.
It would seem that until such time as Paul Avis licenses or sells his patent, no one else can manufacture and sell these without the risk of patent infringement.
Tweakie.
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It is a shame if he is not moving to produce them. To just sit on a patent is kind of senseless but who knows what is going on.
I was thinking of making one but I am a little stumped as to how to machine the exact profile without a CNC lathe or grinder of some sort.
I dont have a vertical CNC controlled axis on my mill yet. I do have a X and rotational CNC axis setup though. Maybe this is the need that will get me to work on one.
I would be interested in hearing from anyone who has made such a gear cutting endmill to see what angles were used in creating it.
Scott
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Hi Scott,
I think that although the endmill gear cutter is a brilliant device it is in many ways very impractical to market. A supplier could, for example, hold a thousand in stock and yet it is unlikely than any one would be suitable for the particular gear a manufacturer is intending to make. This is because the gear tooth profile and, more importantly, the shape of the gap between the teeth (and therefore the final shape of the endmill cutter) will be different for any given diameter / number of teeth and the contact angle of the gear (the portion of the involute curve forming the tooth profile is always linked to the pitch circle diameter of the gear). The picture below, perhaps rather extreme, shows to illustrate the difference in teeth profile between two gears which both have the same D.P. but differing number of teeth and therefore diameter. The endmill gear cutter could, I think, only really be a product ‘made to order’ once the size and parameters of the gear has been established and then another endmill gear cutter would have to be ordered for the meshing gear (if it was not identical to the first) and so on.
If you are up for a challenge and plan to try making one of these endmills then just as a suggestion:- An online gear profile generator can be found here http://woodgears.ca/gear_cutting/template.html once you have entered your parameters download the gear in HPGL. From the resulting file delete the first part (up to the second instance of SP1) it can then be opened into LazyCam. By deleting the unwanted chains and entities you will be left with the profile of ½ a tooth – from which you could produce the GCode toolpath for the exact shape of the endmill cutter. Milling it is another task (but not impossible) then cutting the flutes and creating the clearances from the cutting face could then be accomplished (4th axis would be nice here) followed by a hardening process. Sounds like quite a major project but it would not be beyond the grounds of possibility.
Incidentally I am no expert on gears, my only experience comes from profile cutting countless gears and escapement wheels for a friend of mine who has an insatiable appetite for designing and building wooden clocks and mechanisms.
Best of luck with the project.
Tweakie.
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I see your point on needing one for each gear if they are not the exact same dia & # of teeth. Thanks for the link to the gear tooth profile generator. I think I had come across it awhile back. My best bet for ease might be to just use a small dia end mill /router bit and just mill the entire gear profile. I just need to get my CNC router completed.
Thanks for all the great help and advice.
Scott
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Scott,
Here is a link which shows some gear cutters that i have made and used. There are actualy two posts and the first post shows how the bit was set and cut. They work fine but it does take time to make them.
Guess it's better than spending $25 a crack when you need one.
There was an arcticle on how to make the ones that that guy is seeking a patent for ( Pracatical Machinist Magazine some time ago )
http://www.machsupport.com/forum/index.php/topic,8118.msg51321.html#msg51321
http://www.machsupport.com/forum/index.php/topic,8120.msg51325.html#msg51325
FWIW,
RICH
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Cool idea! I never thought of fly cutting them. Nice pictures.
I wonder if I could make one to fit a small fly cutter that could be mounted in a router. Slowed down a lot of course.
Scott
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I would advise against putting any tool into a router that is not perfectly balanced.
I would also advise against slowing down a router with a rheostat.
http://www.machsupport.com/forum/index.php/topic,13270.0.html (http://www.machsupport.com/forum/index.php/topic,13270.0.html)
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I echo Sam's reply.
I modified a small fly holder such that the cutter would be parrallel to the table and ran it at 1000 to 2000 rpm.
That's the reason for the dimensioning of the cutter since you to need to accurately set it up. They were done quite accurately with the proper point width for the correct total depth. For small stuff / model work they do the trick. We have used then to cut timing belt gears ( that's different story!). Actualy you can just use the spead sheet and find a close radius and mill the radius but then it would be used only for matching gears sets. I will note that probably better to just buy a gear cutter otherwise if accurate tooth profile / engagement is required as it does take time to make them.
RICH
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I definatley agree on making it a balanced tool. I used to work at Ingersoll Milling Machine company and designed a few carbide insert tools while there. I have seen what can happen when they are not balanced and especially at 30,000 rpm 30Hp. The nice thing with inserts is that they have a pocket and screw in the center (on some) that retain the insert. As for slowing down my router it has a built in variable speed dial. It is a Makita 1/2" variable speed plunge router. I am not sure though how slow it would go. I think my best bet will to just get a small dia router bit and cut the profile of the gear in 2D.
Thanks
Scott
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just get a small dia router bit and cut the profile of the gear in 2D.
That works if it is an accurate machine..........
RICH
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Hi Scott,
You will find that when 2D profiling the endmill diameter will pose a limit on the smallest diameter / maximum number of teeth that can be made.
I was using a 1mm dia cutter for these parts and they are probably better described as cogs than they are as gears. They were just fine for their intended purpose but it would not be a practical manufacturing process for say replacement gears in a Futaba servo.
Tweakie.
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I know this is an old post but has anybody done any gear from generation then one flat sided angled end mill could be used to generate any tooth number gear
Brian
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I am not sure I follow what you are talking about. Can you desribe the end mill further?
Thanks
Scott
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Brian,
As I mentioned earlier in this thread, the cutter shape would have to be different for each gear having a different number of teeth.
This is because the gear tooth profile and, more importantly, the shape of the gap between the teeth (and therefore the final shape of the endmill cutter) will be different for any given diameter / number of teeth and the contact angle of the gear (the portion of the involute curve forming the tooth profile is always linked to the pitch circle diameter of the gear).
Tweakie.
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Its along the lines of this.
Instead of forming the involute curve we can generate it. One way of doing this is to use the involute form that has an infinite base circle diameter i.e. a rack; where the form is a straight line at an angle; much easier to manufacture the cutter.
If we then produced an end mill with this form, it would be just like a truncated ‘V’ tool or a single tooth from a rack of the correct modulus.
Now the first pass of this cutter, on the centre line of the gear, would produce a like for like tooth form but if we then rotated our work piece a small amount and our cutter the correct linear distance away from the centre line; as if the gear and the rack where messing, then the gear tooth would become more accurate. The accuracy depending on how many increments we decided to do. There would also need to be some allowances many for clearances etc.
I know this would be time consuming and the process would have to be repeated to generate the other side of the tooth but potentially a very accurate gear could be produced.
I am not expert enough with Gcode or Mach3 to know how to control the tool path but the geometric relationship between the part rotating and the tool moving is relatively simple.
As side note I remember going on a factory tour of Borg Warner, here in South Wales, back in the late 70s, before CNC was invented :-) it was part of my T6 City & Guilds college course in Production Engineering. I remember them doing this but with mechanical controls and the tooth form was being ground. I remember they had more ways of producing gears than you could shake a stick at.
Brian
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Brian,
Thanks for explaining - I now see exactly what you mean, this method would be an excellent way to make gears (and even I could grind the correct shape cutter). ;D
This would simplify things a lot as only one cutter would be required for each D.P. of gear.
Tweakie.
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That sounds like it would work. About taking more time to cut though it seems like I have little free time but the price is also free so if I can do it myself as cheaply possible I like it.
Thank you for explaining it more. I am not a gear wiz in any way shape or form but I would like to make some gears from time to time and dont want to buy a cutter that is more expensive than the 1-2 gears I want to cut with it.
Please post back if you give this a try or Tweakie.CNC if you make one I would like to hear how it turns out.
Thanks
Scott
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Scott,
There was an article in one of the magazines ( Home Shop Machinist ? ) some time ago about the single cutter you mention in your first post or that video. It talked about how to make and use it for different gear sets. Was interesting, i'll see if i can find it in my vaults of how to's....
RICH