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Author Topic: Gear cutting end mill search  (Read 18895 times)

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Offline RICH

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Re: Gear cutting end mill search
« Reply #10 on: March 24, 2010, 09:46:25 AM »
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
Re: Gear cutting end mill search
« Reply #11 on: March 24, 2010, 08:12:03 PM »
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

Offline RICH

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Re: Gear cutting end mill search
« Reply #12 on: March 24, 2010, 08:48:18 PM »
Quote
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

Offline Tweakie.CNC

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Re: Gear cutting end mill search
« Reply #13 on: March 25, 2010, 05:37:46 AM »
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.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Gear cutting end mill search
« Reply #14 on: July 06, 2010, 02:35:05 PM »
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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
Re: Gear cutting end mill search
« Reply #15 on: July 06, 2010, 09:46:46 PM »
I am not sure I follow what you are talking about. Can you desribe the end mill further?
Thanks
Scott

Offline Tweakie.CNC

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Re: Gear cutting end mill search
« Reply #16 on: July 07, 2010, 02:11:01 AM »
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.

Quote
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.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Gear cutting end mill search
« Reply #17 on: July 07, 2010, 05:03:57 AM »
.
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 ā€˜Vā€™ 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

Offline Tweakie.CNC

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Re: Gear cutting end mill search
« Reply #18 on: July 07, 2010, 05:40:28 AM »
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.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Gear cutting end mill search
« Reply #19 on: July 07, 2010, 11:33:09 AM »
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