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Small Gear Cutters

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John Stevenson10/08/2011 23:35:19
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5068 forum posts
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Art Fenerty of Mach3 and Gearotic fame has brought a new module out for Gearotic.

Because there is a limitation on how small a gear you can cut due the the size of the cutter another way was needed to generate small gears,
As an example for a 32 DP 40 tooth gear, common on small model IC engines you need a 28 thou cutter, if you drop down to 48 DP you need a 19 thou cutter.

Not impossible but probably expensive and time consuming.

The new module adds Tool Wizard in which you specify a round blank and various hocus pocus like cutter used feed rates etc and it mills a flat on the blank, then rotates it 180 and mills a second flat.
It then tilts to a desired angle, 9 degrees is default and the side of the cutter profiles the tooth space.
This 9 degrees will give the necessary clearance for the cutter once hardened.

So basically what you get is a spade bit with two cutting edges.



This isn't one cut with Gearotic but it's similar to what you will get but a bit more accurate than the hand ground one.

You will be able to make the exact cutter you need for the size and tooth count of the gear, no 21 to 25 teeth banding, basically an end mill for every size.

Hope to show some finished blanks later.

John S.
Phil P11/08/2011 08:59:26
851 forum posts
206 photos
John
 
Is that to be used as a fly cutter or an end mill.
 
 
I have been wondering about making something along similar lines to single point fly cut new worm wheels for musical boxes, but using the Mikron hobber instead of milling.
 
Phil
John Stevenson11/08/2011 09:03:48
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5068 forum posts
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Designed to be used as an end mill but could be used as a flycutter.
 
I need to have a play with this in metal instead of just virtual, problem is the mill is setup on a job I don't want to disturb.
 
For a worm wheel surely you would need a straight sided cutter with no involute ?
 
John S.
 
Edit, forgot to mention it can also do timing pulley profiles as well as involute gears.
Normal trapezoidal shape like XL and also HTD and T series.
 
XXL series.
 
 
HTD Series.

Edited By John Stevenson on 11/08/2011 09:16:33

Phil P11/08/2011 13:17:46
851 forum posts
206 photos
John
 
A musical box worm wheel is a very oddball thing, it is more akin to a clock escape wheel, but with its teeth cut to match the helix angle of a very slender worm.
 
Phil
Simon036228/09/2011 15:21:19
279 forum posts
91 photos

John,

Very interesting - so much so that I have just downloaded the demo - but I can't find the Tool Wizard module. Is this only available to those having a full licence or am I just not looking hard enough? [see below...!]

Thanks,

Simon


I self-diagnosed the problem...I was not looking hard enough. Anyone else should create the wheel in the project database and then right-click on the wheel name - this brings up a short menu including 'tool wizard'. Easy when you know how


Edited By Simon0362 on 28/09/2011 19:16:14

Philip Burman28/09/2011 21:03:20
16 forum posts
I have had several goes at making the cutters using Art's Gearotic programme. Cutting the involute on the cutter works great but the rest of the geometry leaves you with a weak cutter. I've managed to break 3 without cutting as many gear teeth. The main problem is that the cutter has constant thickness and this thickness cannot be greater than the width of the gear root, which for small module gears is a fraction of a millimeter. Art's working on it and I'm sure he will get there in the end. My conclusion, for what it's worth, is that he should use the gcode to produce the involute profile on a flycutter. We will see.
 
Phil

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