# Cutting my first gear



## Brian Rupnow (Jun 13, 2010)

I was so inspired by Captain Jerrys post about gear cutting in his thread about the donkey engine, that I thought I might try it. I have never done this before, so it will be a total learning experience for me. Jerry refers to this excellent website in his post
http://www.rushgears.com/Tech_Tools/PartSearch5/partSearch.php?gearType=SPUR
which will let you configure the gear to what you want, and then let you download a 2D or 3D file of it to use on your computer.


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## Deanofid (Jun 13, 2010)

You'll get it, no prob Brian. 
Like Linda Ronstadt says;
It's so easy, so easy, so easy, so easy...


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## Brian Rupnow (Jun 13, 2010)

I went to their website, and chose a 24 pitch, 20 tooth, spur gear with a pitch diameter of 0.833 and an overall diameter of 0.917"---This was determined more from the fact that I have a scrap piece of 1" o.d. aluminum round stock than anything else. The gear downloads very nicely, and they even have an option for downloading it in solidworks


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## Brian Rupnow (Jun 13, 2010)

Once I had the solid model of the gear on my computer, I started a sketch on the face of the gear, and converted the lines adjacent to the gap between two teeth to "line entities" and decided that a piece of 3/16" square HSS would be large enough.


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## Brian Rupnow (Jun 13, 2010)

I then extruded those line entities into the third dimension (thus 3D) and created my cutting tool 'In place".


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## Deanofid (Jun 13, 2010)

Brian, in case you haven't come across it somewhere, there's a simple formula for finding
gear blank diameter. Take the number of teeth you need, add the number two, divide by the gear pitch. Try it with the one you just put up, and you'll see what I mean.

Dean


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## Brian Rupnow (Jun 13, 2010)

Then I pulled the newly created cutting tool onto a drawing sheet, and began to generate dimensions from the math data which is captured in the solid model when I create it.


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## Brian Rupnow (Jun 13, 2010)

At this point I have all the information I need to build a cutter which will exactly replicate the cut in a gear blank identical to the gap between the teeth in the "parent" gear. No provision made as yet for relief angles.


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## Brian Rupnow (Jun 13, 2010)

Although what I just done was the "high Tech" version of it, I am sure that many gears have been built by tracing the profile from an existing gear, and then replicating it. I think it will be quite a challenge to grind this profile correctly without a "visual comparator" which will project the profile of what I attemp to grind onto a much larger screen where my results can be "compared" to the theoretically perfect profile. and I don't even know where to start in terms of relief angles.


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## tel (Jun 13, 2010)

Brian Rupnow  said:
			
		

> Although what I just done was the "high Tech" version of it, I am sure that many gears have been built by tracing the profile from an existing gear, and then replicating it. I think it will be quite a challenge to grind this profile correctly without a "visual comparator" which will project the profile of what I attemp to grind onto a much larger screen where my results can be "compared" to the theoretically perfect profile. and I don't even know where to start in tems of relief angles.



Get hold of a copy of Ivan Laws' book and your troubles will be over, or just beginning!


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## Deanofid (Jun 13, 2010)

Brian Rupnow  said:
			
		

> I think it will be quite a challenge to grind this profile correctly without a "visual comparator"



It can't be that hard. It's done all the time by people like Tel, me, Jerry, and so on. Properly ground
single point gear cutters have been done this way for generations.


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## Captain Jerry (Jun 14, 2010)

Brian

I still have a lot to learn about gears so I want to follow this thread. For practice, I created and downloaded the same gear spec from the rush site and worked up the drawing as before. I was surprised to find a significant difference in a critical dimension. Your drawing shows the angle between the opposing gear faces of 72.89 degrees. On my workup I found the critical angle to be 44.59 degrees. 

With a little effort, I found the reason for the discrepancy. The lines that you have constructed are tangent to the gear face at the TIP of the tooth, and the line that I have constructed is tangent to the face of the gear at the midpoint of the tooth face.

The reason that I chose the construct that I did is that it lets you grind a "V" point on the tool blank to this angle that you can very easily measure. From that point to get to the final profile, you only need to remove a VERY small amount of material from the flat face. That's the purpose of the small diameter stone that I used. The full face of the stone provides the correct radius. No fancy measuring equipment needed!

I hope this doesn't confuse the issue too much. I'm only trying to make it as easy as possible. My workup drawing is attached.

Jerry

EDIT. I also attached a PDF file that can be enlarged with better detail. 






View attachment Alibre Design Drawing of brians gear.pdf


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## Brian Rupnow (Jun 14, 2010)

Jerry---this is as close as I could get to the shape of your cutter


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## Captain Jerry (Jun 14, 2010)

Brian,

That looks pretty good. Why do you think the tooth face radius has changed from .165 in the model view to .17. Is that from rounding to two places?

I think you will agree that it is no real problem to grind a flat sided shape that is pretty close to the finished shape. The difference between 44.59 deg and 43.51 deg is pretty slim and if you can get anywhere in between it ought to work just fine. I don't know what you call the area that is between the chord and the subtended arc of a circle but maybe Marv can tell us. That small area is not all that hard grind off. Wear your safety glasses and get in close and watch it come to shape. The small radius at the end is a non-contact surface and is for clearance only so its not all that critical.  The only thing you need to worry about now is the relief angles. A few months ago, you showed a tool grinding fixture. You ought to be able to adapt something like that. If the straight sided cutter has a few degrees of relief it makes it easier to keep that angle as you grind away the little unnamed arc.

Top rake is important too but that is handled by the tool holder design. Brass and Aluminum don't need much top rake but a few degrees of top rake seems to reduce the pounding at the start of the cut. I have not tried to cut a steel gear yet but my guess is that top rake would more necessary.

I hope this is helpful. I'm a little uncomfortable sounding like an expert. On my donkey build thread, I was just showing the approach that I took. If you were influenced by that experience I just want to be more clear about what I was attempting to do.

Jerry


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## mklotz (Jun 14, 2010)

> I don't know what you call the area that is between the chord and the subtended arc of a circle but maybe Marv can tell us.




It's called a circular segment

http://mathworld.wolfram.com/CircularSegment.html


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## Brian Rupnow (Jun 15, 2010)

After thinking this through, I may have shot myself in the foot first thing!!! My rotary table rotates through 4 degrees with one complete turn of the handle. Although I did buy the divider plates along with a tailstock when I bought the rotary table, I don't (at this time) have the faintest idea as to how to use them. So---I would like to cut a gear that will require full complete turns of my rotary table handle between each tooth. This is where it gets a bit strange--A 20 tooth gear will have 18 degrees between each tooth. 18 is not evenly divisible by 4, so this means 4 1/2 turns of the handle between each tooth. What I want is for instance, four complete turns. This would mean 16 degrees between each gear tooth, resulting in a 22 1/2 tooth gear!!!--So thats out. If I work with 3 complete turns of the handle, that would mean 12 degrees between each tooth. 360 is divisible by 12 evenly, giving me a 30 tooth gear. so---perhaps I will start with a 30 tooth gear instead.


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## mklotz (Jun 15, 2010)

Limiting yourself to only divisions that are integer multiples of 4 deg will severely cramp your gearmaking possibilities.

The plates you bought allow you to use your RT as a dividing head. Download my DIVHEAD program and read the simplified description (about four paragraphs) of the computations involved, set up the data file for the hole plates you have, and the program will do all the math for you.


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## Brian Rupnow (Jun 15, 2010)

Marv--I'll save that for another day. With a little more cogitation, I realized that an 18 tooth gear will have a seperation of 20 degrees between each tooth (360 / 18=20). And that twenty degrees is evenly divisible by 4, so that calls for 5 full complete turns of the handle on my rotary table at 4 degrees per turn to give the even twenty degrees of indexing from tooth to tooth.
With that in mind I went back to the gear website and downloaded the profile of a 24 Pitch, 14.5 degree pressure angle,18 tooth gear, with a p.d. of 0.833" and an o.d. of 0.917"---------this means I can still cut it out of my 1" diameter piece of aluminum. So---here is the gear profile with the edges of the gear converted to "line elements" and used to establish a drawing of the appropriate cutter.


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## Brian Rupnow (Jun 15, 2010)

Here we have it with the sketch extruded into the third dimension---


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## Brian Rupnow (Jun 15, 2010)

And here we have the detail drawing of the cutter. This will get developed more before I decide how to machine/grind this exact profile, but this is my starting point. I now have to figure out how to add some draft to the sides and how to grind the radius with a relief included.


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## Brian Rupnow (Jun 15, 2010)

With a little judicious grinding, I can get most of the profile required in two steps, as per the drawing---


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## Brian Rupnow (Jun 15, 2010)

So, I start with a piece of 3/16" square HSS and grind it as per the drawing--


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## Brian Rupnow (Jun 15, 2010)

Then I dress a mounted point (small mandrell mounted grindestone) to 0.298" dia. and blast away on the sides of the cutter as per the drawing---


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## Brian Rupnow (Jun 15, 2010)

So, Captain Gerry---Am I close so far to what you did?---And if I am, how much relief angle did you add in?-----and did you add relief angles to the large radii???----Brian


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## kvom (Jun 15, 2010)

I have been wondering if there is any disadvantage (other than tedium) of using a RT as a dividing head without plates.

It would be easy to write an Excel spreadsheet to calculate each interval's degrees/minutes/seconds. You could then just move the RT directly using the dials. Obviously slower than the plate method, and you'd have to manually locak the table each time.

Comments? (FWIW, my RT doesn't have the plates)


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## kustomkb (Jun 15, 2010)

Nice job describing your thought process Brian.

Kvom,

 I think your eyes would get a pretty serious work out dialing a rotary to the second for every tooth. It's the plates which give you the accuracy. 

Brian,

Here is a nice write up on how top use your plates, there's not much to it, if you take the time to read it. In the end you will have much more accurate gears and the process will go much quicker;

http://igor.chudov.com/manuals/Troyke-Rotary-Tables/UsingARotaryTable.pdf


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## Brian Rupnow (Jun 15, 2010)

Kvom--Are you reading my posts? That is exactly what I am proposing to do----Not use the divider plates.


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## Captain Jerry (Jun 15, 2010)

Brian Rupnow  said:
			
		

> So, Captain Gerry---Am I close so far to what you did?---And if I am, how much relief angle did you add in?-----and did you add relief angles to the large radii???----Brian



Brian,

You are right on track. That looks good. I did add relief to the large radius. If you don't, the cutter will drag its heel through the cut. There must be at least that much relief added in the long dimension. Side clearance is also important. You can do both at the same time with the setup that I used.

Left Side:





Right Side





With the table angle set to 10 degrees and the toolbit in the small vise, if you were to point the tool parallel with the front edge of the table (pointing straight up the slope) the resulting grind would leave you 10 degrees of relief in the long dimension.  By angling the tool so that it points uphill at about 30 degrees with the slope, The resulting grind provides side relief at the same time. You only need to watch the profile on the top of the cutter. The relief angles take care of themselves. 

The last step is to point the bit straight up the slope into the stone and take the heal of the end, leaving a 10 degree relief at the tip. I found it easier to grind the small radius as the final step (after the last step). 

I knew when I showed this method in the donkey build thread that I was giving it a once lightly, and since it didn't draw any questions, I was pretty sure I hadn't explained it very well. I hope I have now but don't hesitate to ask if its still not clear.

Jerry


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## Brian Rupnow (Jun 15, 2010)

Jerry---thanks!!! How did you establish your angles? The field of play is too small to lay things out on the 3/16 piece of HSS (other than perhaps a centerline.)---Brian


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## Captain Jerry (Jun 15, 2010)

Brian,

I just realized that the gear you are making is closer in size to the pinion that I cut. These pics show the same thing only using a smaller diameter stone closer to the one you will use,











You will really like the dividing plates. They are a bit of a mystery but once the light comes on you see what I mean.

Jerry


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## Captain Jerry (Jun 15, 2010)

Brian,

The table angle sets the front relief. I just eyeballed the side angle. Its not so critical. I guess you could clamp a straight edge to the table if you want.

Jerry


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## Dan Rowe (Jun 15, 2010)

Brian,
Thanks for posting your gear cutting adventure. I bought a shaper for this type of gear work but I have never put it to use yet.

Jerry, I think that I followed your first explination but thanks for adding it to this thread with more detail.

Kvom, The plates I have for my RT do not have every division between 2 and 100. It has most of them but not all so if an odd prime number gear was needed the only option would be by degrees.

Dan


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## Brian Rupnow (Jun 15, 2010)

Jerry---I am setting here reeking of gasoline (I was out of Varsol) from cleaning the cosmoline off the divider plates which I bought with my rotary table 3 years ago. I am reading the Chinglish literature that came with them and scratching my head trying to make sense of it.---Again, I ask---How did you establish your side angles when you ground your HSS? surely you didn't lay them out on the HSS and "grind to the line"???


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## Brian Rupnow (Jun 15, 2010)

Gerry---Sorry---We were both typing at the same time I guess.


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## mklotz (Jun 15, 2010)

Dan Rowe  said:
			
		

> Kvom, The plates I have for my RT do not have every division between 2 and 100. It has most of them but not all so if an odd prime number gear was needed the only option would be by degrees.



Dan,

You don't need a hole circle for every division. As an example, given an RT with a 90:1 gear ratio (what Brian has) you only need the following hole plates...

Hole plates required for all divisions up to 50
3,5,13,14,16,17,19,22,23,29,31,37,41,43,47,49

to obtain all the divisions between 2 and 50.


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## Brian Rupnow (Jun 15, 2010)

And here we have a prime example of the "quality" of imported Taiwanese machinery. My rotary table, purchased thru BusyBee Tools in Canada, and proudly manufactured by the Tzu Yen Industrial Company Ltd. trademark "Yiyen" with a nameplate decrying "PRECISION MACHINE TOOL" sells a set of divider plates with their rotary table which only vaguely matches the tapped holes in the rotary table. Damn, Damn, Damn!!!! The only good thing here is that the center bore on the divider plates is a very good fit on the spigot of the rotary table. I guess that before I do anymore set-up with my divider plates, some hole slotting will be in order.


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## Captain Jerry (Jun 15, 2010)

Brian,

There are some guidelines that could be layed out on the top of the tool bit. If you coat the bit with dye you could mark the centerline and the two cross lines at each end of the large radius. I did not do this but it has been recommended on other threads. You might find them usefull. See the attached PDF.

Lets see the holder that you will be using for the bit.

Jerry 

View attachment Alibre Design Drawing.pdf


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## Brian Rupnow (Jun 15, 2010)

Thanks Jerry---I'll probably be doing some of that---I'll post a pic when I get that far.---Brian


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## Brian Rupnow (Jun 15, 2010)

I am sure that there must be some great irony involved in using an imported Oriental milling machine to correct the mistakes in an imported Oriental indexing plate, however, its done. All the parts assemble just like in the pictures in my Chinglish brochure, and fortunately 18 divisions is one of those numbers that you can use any of the dividing heads for. I won't be using both arms of the brass sector?? part, but will use one of the arms as a "witness" to make sure I always get the pin back in the same hole after 5 revolutions. My rotary table gear ratio is 90:1, so 5 full rotations of my handle will give exactly 20 degrees, which is 1/18 of 360 degrees.


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## Brian Rupnow (Jun 16, 2010)

Here we have a piece of 3/16" square HSS, with the requisite layout lines on it.---Pretty darn small, isn't it. I think I'm going to build a simple jig for the 22.5 degree angle on each side and grind them on my bench grinder, using the fixture I made up to grind lathe tool bits.


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## Brian Rupnow (Jun 16, 2010)

If you were wondering how I was going to cut that 22.5 degree angle, with a relief----Heck, even in case you weren't wondering--here's how I do it. The pedestal in front of my grinder is fixed at a permanent 7 degree angle. It has two 3/4" wide slots in it that are parallel to the sides of the grinding wheel. I take a piece of 3/4" square aluminum stock, set it up in my mill with my swivell based vice, and mill a slot (2 slots actually) through it 3/16" wide at 22.5 degrees. This lets me nest the HSS in the 3/16" slot in the 3/4" square bar, which in turn sets in the slots in the pedestal, and presents the HSS at a perfect angle to grind 22.5 degrees with a 7 degree relief angle. When one side is done, I flip the guide around, set it in the other slot, and grind the other side of the HSS.


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## Captain Jerry (Jun 16, 2010)

Hey Brian,

From an existential point of view, what's the sound of one gear meshing?


Jerry


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## Brian Rupnow (Jun 16, 2010)

Here we are after the "first grind"---Jerry---Thats kinda like "If a gear meshes in the forest, and nobody hears it mesh"----


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## Captain Jerry (Jun 16, 2010)

Brian

That grind looks perfect.

What I was trying to say is that when you are turning up blanks for your gear, be sure you make more than one. That first gear is gonna want a mate real quick.

Jerry


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## Brian Rupnow (Jun 16, 2010)

So here we are, all set up to grind our radii. Same set-up as Captain Jerrys. only his machinery is cleaner. The drill press table is tilted 7 degrees, I was able to turn a 3/8" mounted point (grinding wheel on its own arbour) down to 0.300 using a carbide in my lathe. I have a guide bar mounted to the drill pres table with a couple of vice grip style clamps. and I will keep the cente of the grinding wheel in line with the tip of the tool . (I have ground a flat on the the tip (with 7 degree relief) as per the last drawing, but I didn't take a picture of that step.) The drawing calls for the center to be offset from the tip by 0.003", but for such a small amount of difference, I'm not going to worry.


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## Captain Jerry (Jun 16, 2010)

Brian,

The guide bar needs to be angled across the table and the point needs to point up the slope to get the compound relief/side clearance. If you grind the way you show it sitting, you will lose your relief angle.

Jerry


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## Brian Rupnow (Jun 16, 2010)

Jerry--I got relief the way I did it also, because the drill press table is angled at 7 degrees. When I moved the vice "up hill" the mounted point began cutting on the bottom side of the HSS first and had to cut a fairly good relief before it started to even cut the top of the HSS. as long as there is chip relief there, I don't think it matters too much if its angled back towards the rear of the cutter, or just in towards the center of the cutter. As far as the grinding itself, I think that everything was "fairly" scientific and repeatable, up untill the last stage of putting that radius in. that part is pretty Hokey---kind of a subjective thing. The blessing of course, is that even if the gear teeth I cut are a little "wonky" they should mesh well with any other gears as long as they are cut using this same cutter. And yes---I will cut a gear long enough that I can part it off into two gears to do a trial run and see if they actually mesh and run. Now I'm off to BusyBee to buy some more of that great Imported technology---I need a chuck to mount on my rotary table. Its a royal pain in the behind to have to steal the chuck off my lathe every time I want to do something on the rotary table!!!


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## Brian Rupnow (Jun 16, 2010)

Before I could go too much farther, I needed to go across town to BusyBee and buy a 3 jaw chuck to mount on my rotary table, bring it home, and make an adapter plate to mount it to my rotary table. Tomorrow I will continue the saga of cutting my first gear.---Brian


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## putputman (Jun 16, 2010)

Brian, I have been following your thread on gear cutting and I can feel your excitement as you get closer to the actual cutting of the gear. I have cut many gears and believe me it is enjoyable and satisfying.

I hesitate to mention this as I do not want to get into a debate on it, but I feel you would have been better off to purchase a 4-jaw chuck instead of a 3-jaw. I feel that once you cut a successful gear, you may be making your own gears for all of your future projects. The 4-jaw chuck is less expensive than a 3-jaw and is more universal and accurate for some possible future projects. 

Example: If you want to cut some more 18T 24P gears with a 1/2" bore for future engines, you can machine the blanks on the lathe and use the same old mandrel to mount the blanks on the RT. A 3-jaw chuck does not repeat close enough, (especially those Chinese chucks) Maybe I am not explaining this clear enough, but I do it quite often and it save a lot of time and material.


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## Brian Rupnow (Jun 16, 2010)

Putputman---Thanks for your input. Although I know everything you say is true, I am a total knob at setting up a 4 jaw. ;D ;D If I ever find in future that I really NEED a 4-jaw, I have a perfectly good one that came with my lathe which has never been used.---Except for one afternoon of complete frustration trying to center it----It was then returned to its box on the bottom shelf and will hopefully stay there untill I am old and dead!!!


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## Brian Rupnow (Jun 16, 2010)

Check this gear making video out.----Perfect---Have your sound on.
I just found this really neat video on "That other" website I hang out on. Its great---shows a man making a gear and using the dividing plates and sector plates. Make sure your sound is on when you watch it.
[ame]http://www.youtube.com/watch?v=VHTXaU7GZC0[/ame]


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## kcmillin (Jun 16, 2010)

That cutter looks great.
Have you made the holder for the cutter?

Also, are you going to shorten the cutter? If so, how are you going to do it?

I have a pretty crude method of breaking mine, but it is very unpredictable. I put it in a vice, cover it with a cloth, and smack it with a BFH. If I dont loose it, I usually end up with something that is not very close to what I wanted. And tiny bits of HSS everywhere.

Kel


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## Maryak (Jun 16, 2010)

kcmillin  said:
			
		

> Also, are you going to shorten the cutter? If so, how are you going to do it?
> 
> I have a pretty crude method of breaking mine, but it is very unpredictable. I put it in a vice, cover it with a cloth, and smack it with a BFH. If I dont loose it, I usually end up with something that is not very close to what I wanted. And tiny bits of HSS everywhere.
> 
> Kel



Kel,

I cut my HSS with a 4" angle grinder and a 1 or 2mm metal cut off disk. I use the same method when making a solid boring bar from HSS, saves a hell of a lot of wear on your fingers and the bench grinder wheel.

All part of Bobs glossary of now why didn't I think of that before I'd buggered something up.

Best Regards
Bob


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## mklotz (Jun 17, 2010)

The angle grinder approach works well. If you don't have one you can do it with your bench grinder.

Using the corner of the wheel, score all four surfaces of the bit where you want the break to occur. Then mount in the vise with the score line about 1/16" above the top of the vise jaws. Cover with a disposable rag and whack with a hammer. The bit will break where it was weakened by the grinding.

Throw the rag away. It may contain minute shards of HSS that can play havoc with your hands if you inadvertently use it to wipe something.


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## Brian Rupnow (Jun 17, 2010)

I spent all morning fighting with my adapter plate which holds the new 3 jaw chuck to my rotary table. When I made that adapter plate a couple of years ago, it was to mount the chuck off my lathe to the rotary table. Of course the new chuck is smaller, had a different bolt circle and a different "register" diameter.---and I don't think things were all that concentric when I made it the first time. This afternoon, after driving all the way across town to buy a 5/8" bolt, I made a holder for my cutter. I was supposed to go to Kitchener tomorrow to measure up a machine for another design contract, but now they have called and said the machine won't be disassembled untill Monday, so I may actually get to making a gear tomorrow.---And---I cut my HSS tooling with a 3" diameter x 1/16" thick abrasive wheel in my pneumatic grinder. So anyways, here is todays progress---


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## mklotz (Jun 17, 2010)

For the benefit of future readers of this thread...

If you don't want to take the time to make a tool holder as Brian has shown, take a length of cylindrical stock of the size of the horizontal hole on your boring head and mill a groove the width of the tool bit down its length. Insert tool and use the boring head setscrews to secure the bit. As an advantage you gain the built-in ability of the boring head to make fine, precise adjustments of the bit extension.

I use this arrangement to do cut knurling on flat surfaces. Recommended.


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## lathe nut (Jun 17, 2010)

Brian, looks like a great job there, now lets see the gear, thanks, Lathe Nut


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## Brian Rupnow (Jun 18, 2010)

Yesterday evening, I turned a blank on my lathe, with the required major diameter of the gear and two areas slightly smaller than the root diameter which would become hubs. While I had the material in the lathe, I also drilled and reamed it for a 5/16' shaft. This morning I got up early and scooted down to my little shop to set everything up.


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## Brian Rupnow (Jun 18, 2010)

Although Captain jerry cut his gear teeth in one pass, either he's a braver man than me, or has a sturdier machine than mine. The difference between the blank diameter and the root diameter is 3/16", meaning a full depth cut would be 0.094" in one pass. I figured my small mill would probably lay an egg if I tried to cut that all in one pass, so my first series of cuts were 0.043" deep. The machine didn't protest too much, and everything worked quite well.


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## Brian Rupnow (Jun 18, 2010)

After my first pass around the gear I dialed in for a full depth cut. My little machine really didn't like that--Thumpa-Thumpa-Thumpa. Damn, I hate those interupted cuts. I have no idea what kind of aluminum I made the gear blank out of, but I noticed that after going all around the gear at a full depth cut, some of the aluminum seemed to be "extruding" for lack of a better word around the crests of the teeth---you can see it in the picture. This was not a big issue, as I took it over to the lathe after it come off the mill and used high speed and a sharp HSS cutter to turn the diameter back to what it should be---and this step cleaned up the outer diameter of the gear very nicely---didn;t look so ragged then.


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## Brian Rupnow (Jun 18, 2010)

At this stage of the game, I'm starting to get really happy about things---the gear looks good, and has cleaned up nicely.


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## Brian Rupnow (Jun 18, 2010)

Now remember---I wouldn't be happy with all this untill I seen my gears meshing. That was the reason I made the gear blank so long. I put it back into the lathe, and used my cut off tool to seperate the blank into two gears, then set them up on shafts in a block which I had drilled and reamed to the correct center distance (equal to the gears pitch diameter. And they mesh beautifully.


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## Brian Rupnow (Jun 18, 2010)

This is my cutter "after the fact"---It survived unscathed, and without any undue drag or wear marks or material build up on it. This makes me think that the 7 degree relief all around was sufficient to the act.


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## crankshafter (Jun 18, 2010)

Hi Brian.
Good to see all worked out. I'v followed this thread and got so inspired ;D. I went the "Hobb-way" and made up a hobb in module1 yesterday. I have to cut he flutes and releaf but that have to wait til over this weekend. Me and junior is heading for Sweden to nigth, just for fun. Was hoping for better wether so we could drive the Porche cab. 1953 mod ;D ;D so it have to be the Volvo.

Best regards
CS


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## Brian Rupnow (Jun 18, 2010)

And yes---We have a video!!!


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## Brian Rupnow (Jun 18, 2010)

A very big THANK YOU goes out to Captain Jerry. Without his awesome section on gear cutting in his Donkey thread, I would never have attenpted this.----Brian


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## SAM in LA (Jun 18, 2010)

Brian,

Nice looking gears.

From you I would never expect anything less.

SAM


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## Brian Rupnow (Jun 18, 2010)

Dragging my heel????


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## Captain Jerry (Jun 18, 2010)

Brian

Congratulations on a successful conclusion. One move victory, one more notch on the stock. As far as I can tell, from other members posts and my own experience, the first thought anybody has after completing their first gear is "Hey, that's not so hard". The hardest step is the first step, deciding to do it. You probably thought about many times. I know I did. I'm glad I helped push you over the edge as I was encouraged by all the previous work shared on this forum.

Your future project list options just got expanded. Enjoy.

Jerry

Just a question about the thumping and the extruded metal carried out of the cut. Did you use any kind of cutting fluid. I usually cut aluminum on the lathe without lube but on the single aluminum gear that I cut, I found that a bit of lube made a big difference. WD-40 helped some and then I used a heavier oilier cutting fluid (don't remember the brand) and It was still better. The brass cut a lot easier so no lube was used.


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## Brian Rupnow (Jun 18, 2010)

I used an aerolsol spray on lube that I have found to work good on aluminum. Its marketed here by Canadian Tire stores, and from reading the can, it sounds a lot like a generic WD40. One thing I didn't do was "stone" the edges of my cutter, as the only stones I have are big flat ones, and I was afraid of stoning away the radius. My mill is not very large---Its a typical Chinese import. The gears turned out very nice, but I'm not sure if I would make them again using a single point tool. I know that you can buy a round cutter that is disc shaped, with about 4 notches in the diameter, which would probably be a lot easier on the machine. This was more of an exercise to "See if I can do it." I hear a lot of people on these forums who have trouble with the gear drives on these Chinese mills, and it seemed to me that the pounding that mine got making these gears is not something I want to repeat.----Brian


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## Dan Rowe (Jun 18, 2010)

Brian,
Thanks for the giving this a try. The method would work just fine for anyone with a shaper in the shop as they are designed to take the punishment of a single point tool pounding away. 

Dan


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## Artie (Jun 18, 2010)

"I am very pleased with the first gears I have cut"..... mate that says it all...... Its one of the items high on my priority list... now that the shaper is up and running its drawing ever nearer. I can only imagine the sense of achievement you got from this. Hoping to join you shortly.

Well done mate.

Cheers Rob


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## Maryak (Jun 18, 2010)

Congratulations Brian :bow:

Another arrow for your bow.

Best Regards
Bob


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## Brian Rupnow (Jun 20, 2010)

You guys have absolutely no idea of how much Hell I am getting for running this post over on the Home Shop Machinist forum!!! I never really realized what a drooling idiot I am untill now------


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## Cedge (Jun 20, 2010)

Brian
I just read through the thread over there and found it pretty typical. There are always naysayers and they tend to be the same group of experts..... every time. I'm glad to know that I too am apparently an idiot, incapable of wiping the drool from my own chin. Now, I've got to go out to the shop and make sure my little Victorian engine even runs, since I now know that I can't possibly single tooth cut gears the way I did it. That substandard spoked gear would give them full blown case of the conniptions. 

The experts are all too willing to tell us the things we already do, can't be done. I've been accused of blatantly lying about the Victorian Project being manually machined, by professional machinists. I now just smile and walk away when one begins his "You can't do that manually" spiel. I often find not knowing my task is impossible makes it so much easier to complete successfully.

Steve


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## doc1955 (Jun 20, 2010)

Brian Rupnow  said:
			
		

> You guys have absolutely no idea of how much Hell I am getting for running this post over on the Home Shop Machinist forum!!! I never really realized what a drooling idiot I am untill now------



Brian I have to agree with Steve!
I have done many a gear in the similar fashion to what you are doing. And there are a few motors out there with a lot of hours on them and my gears are still holding up just fine. Don't let some one tell you you can't do something just because they have not tried to.
I've been a design engineer for a long time now and came from a tooling shop before that and have listened to new designers come and spout off how you can't do this and you can't do that. I agree if you are going to push things to the limit they may be right but most times they aren't. I have seen a lot of people spout off and though the years I've noticed the more they spout off the more they lack in general knowledge.

So I say keep doing what your doing, you have done a great job so don't let them BS you.


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## Artie (Jun 20, 2010)

Gday Shred, Id have to disagree... I know a few of them from other sites. They do put out some great work... I think they just arent game enough to display it... might be a reason for that.... from what Ive seen on Brians thread.... would certainly make me think twice....


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## Maryak (Jun 21, 2010)

Brian,

I have just had a look at your post and replies, (well as much of it as I could stomach), over on HSM.   

If I were making a gear set for a nuclear sub to run silent and deep then the comments over there are valid. Then again who in hell would use a milling machine, with any type of available cutter, to make high precision gears for any application. ??? ??? ???

Brian you did a great job at minimum cost with a more than acceptable result for the applications we are most likely to encounter with our models. Hats off to you and to Jerry.

Best Regards 
Bob


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## John S (Jun 21, 2010)

There is nothing wrong with flycut gears IF the cutter is made correctly and to the constrains laid down by the way gears work like OD, number of teeth and depth.

If any of these are ignored you might as well cut the teeth with a slitting saw or use pin and lantern wheels.

John S.


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## SAM in LA (Jun 21, 2010)

Brian,

Keep up the good work. Thm:

I learn so much from guys like you that "don't know what they are doing". :idea:

When you post messages, I consider class to be in session. *discussion*

My dad used to say that the guys in the locker room that brag the most about there exploits are the ones that are getting the least, if you know what I mean. scratch.gif

Respectfully,

SAM


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## shred (Jun 21, 2010)

Artie  said:
			
		

> Gday Shred, Id have to disagree... I know a few of them from other sites. They do put out some great work... I think they just arent game enough to display it... might be a reason for that.... from what Ive seen on Brians thread.... would certainly make me think twice....


You are correct.. I was overly rude to several of the good people on the HSM forum that are both helpful and productive (Mr Stevenson included). I apologize to them as it was a comment addressed not particularly at Brian's thread.


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## Dan Rowe (Jun 21, 2010)

Brian,
I read the other thread and some interesting points were made that I had to take some time to think about.

I down loaded the dfx version of the Rush gear site here:
http://www.rushgears.com/Tech_Tools/PartSearch5/partSearch.php?gearType=SPUR

I set the drawing to show all the points and the gear curves are circular segments. I do not have Ivan Laws gear book but the method of using disks to make cutters has appeared other places. I can not remember the name of the gent who presented it in "Strictly IC" several years back, but i did not grasp it at the time.

Most of the methods using form cutters whether they are commercial cutters or not are only approximate methods. The commercial form cutters cut a range of gears which even if the involute curve is accurate for the middle of the range it would not be precisely accurate for the ends of the cutter range.

I located the centers of two adjacent circular segments and here is the drawing.

The single tooth in the upper section of the drawing is the Rush gear in black and a generated profile in red. The red profile was generated with a program that will generate most gears with standard geometry and a few modifications can be made.
http://delphusa.com/index.htm

I had to really get in close to see the difference of the two teeth in the section of the curve above the pitch circle. The only difference is the part below the pitch circle. There is slight undercutting with the generated gear and with any form cutter this will have to be ignored.

Thank you again for trying this and giving all us gearheads something to think about.
Dan


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## Foozer (Jun 21, 2010)

I read all of your post, find them informative and useful. This play by play of gear cutting you presented is clear and concise enough to encourage myself to give it a shot. It is understood that the gear formed through this method is not perfect, probably will sing a little, gives it character. You formulated and tried a method to produce a workable gear for what this forum creates within the overall equipment theme, a small mill and lathe.

So if you feel like a drooling idiot your not alone. If i can get two pieces of turned metal to be happy bedfellows I'm doing the "Look What I can Do" dance. In the end the only one I need to please is ME.

Why I like to read the info this forum presents. Those like yourself that present workable options and others who suggest without criticism alternative methods.

Robert


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## Brian Rupnow (Jun 22, 2010)

This thread has taken on a life of its own, far beyond what I ever intended. My only desire was to try and make a gear using Captain Jerrys method. After I had ground my cutter Captain Jerry contacted me, and informed me that the angle on which I ground the radii was NOT THE SAME as the way he had ground his. I decided to use my cutter "as it was" without regrinding the radius area. I was not particularly overwhelmed with the results I got, although I did make gears and they did work. In no way did I intend my post to sling any mud or doubt on Captain Jerrys achievement. Perhaps the relief angle on the radius has far more effect on the way how well the cutter works than I had anticipated. Perhaps the unknown piece of aluminum I used to cut my gears from was one of those grades of aluminum that would far rather "smear" than cut cleanly. I'm not sure. However, the bottom line is that Captain Jerry seemed to have a greater degree of success than I did.---His gears look spectacular!!!---So---if you ever want to cut gears, don't look for a way to do it based on my experience, because I have had it pointed out now by informed people from four or five different countries now that my gear making abilities are sub par.


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## kcmillin (Jun 22, 2010)

Brian, I think your go at making gears is a complete success. 
With all the thought and number crunching you and Jerry have put into the project at hand, these gears turned out to be, IMHO, quite excellent, and very well thought out.

It is such a great thing you guys are doing. Taking something that most think is an unreachable goal, and making it a feasible project for anyone with the gumption to attempt it. 

Bravo to the both of you.

Kel


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## kcmillin (Jun 22, 2010)

Now, I'm not intending to hijack your thread. I have some pics of an attempt at making gears. 

[size=10pt][size=10pt]*Sayers of Nay. Watch carefully. Science free Zone.*[/size][/size]
There was no foresight into this, Just an evil eye, and heavy dose of optimism. 

Here is the cutter I made. It is not a single point cutter, but it should apply the same. I made it out of CRS and to heat treat it I just got it really hot and then quenched it. (Pretty scientific, huh?)

Anyway, when I made the shape of the cutter, it was freehand on my mini lathe. With a close eye I was able to get a small gear like cutter. No dimensions were used. You can see that both sides of the cutter are not even the same.









Here are some of the gears I made with them. They were all made with the same cutter. (this is impossible from what I read on the net). 

The larger the gears got, the shallower I had to make the cutter cut. 
I started with a one inch diameter piece, I cut one tooth, and then advanced the R/T to the nearest divisible degree until it looked good to the eye, and proceeded to cut the rest of the gear.

When it came time to figure the diameter of the gear blank, I divided 1 inch by the tooth count I had just cut, and that was my percentage for the rest of them. 


















OK, I know what your saying. 

But Kel, do they mesh?

Well, you tell Me.




Don't let anyone tell you that you cant do what you have already done.

Perseverance is everything.

Kel.


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## Dan Rowe (Jun 22, 2010)

Brian,
There might have been fault in your cutter design but I think the basic aproach is sound of using the Rush Gear drawing as a basis for the design.

For some one that has Ivan Laws gear book does it have a button method solution for a #6 cutter for 17-20 teeth or does it have a seperate solution for each tooth count?

The Rush Gear drawings have a different circular segment for each of the gears made by a #6 cutter. I have started a drawing that shows all the Rush drawing data for a 24 pitch 14.5 pressure angle gear with 17, 19 and 20 teeth to complete the set cut by a #6 cutter.

If there is any interest I will post the drawing with the compareson to the generated gear teeth.

I will be starting my own post with pictures of my first failed attempt to generate a gear with the next attempt awaiting the tooling on its way to my shop.

Dan


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## Maryak (Jun 22, 2010)

Dan Rowe  said:
			
		

> For some one that has Ivan Laws gear book does it have a button method solution for a #6 cutter for 17-20 teeth or does it have a seperate solution for each tooth count?
> 
> Dan



Dan,

Ivan Laws book offers a set of tables for a 1 DP gear with a 20 deg and a 30 deg pressure angle.

For a #6 17-20 20 deg PA

Button Dia = 7.8"

Button centre distance = 8.7"

Infeed = 3.44"

My understanding is for other DP's divide the above by the DP e.g. for a 24 DP #6 cutter

BD = 0.325"
BCD = 0.363"
INF = 0.143" 

IMHO you could have made a rack form hob and be cutting the gear before you have even finished the tool to start making the cutter and then of course you have it all to do again if there is any sort of ratio involved in your gear set.

Best Regards
Bob


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## Captain Jerry (Jun 22, 2010)

Maryak  said:
			
		

> IMHO you could have made a rack form hob and be cutting the gear before you have even finished the tool to start making the cutter and then of course you have it all to do again if there is any sort of ratio involved in your gear set.
> 
> Best Regards
> Bob



Bob, what am I missing here. I think I understand that a single hob can cut all tooth counts for a given DP so to make any working pair of gears, you only need one hob. Is that correct?

For all the dissension that a circular pattern tooth face seems to draw. Is the stepped face produced by a hob, better or worse? 

At my age, hardening is an unfamiliar process and if it occurs, I immediately leave the shop. But that alone keeps from taking the hob path. I know...I should learn.

My next gear making project in the very distant future will involve bevel gears on shafts that intersect at an angle greater than 90. (160 degrees actually). They will need to have a diameter somewhere between 1.5" and 2.5". The tooth count is not critical as they will be the same. Is it possible to make this kind of gear using a hob?

This is not a casual question but is an actual project that I am thinking about when I need an escape from the donkey. Your opinions are highly regarded.

Jerry


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## gbritnell (Jun 22, 2010)

I'd like to comment on a couple of things as I am following this thread.
 Kel, if you made your cutter from CRS you can't heat and quench it to make it hard. It doesn't have enough carbon in it. You can do that with drill rod. With CRS you have to carburize it, in other words you have to heat it and apply a carburizing agent on it then heat and quench it. The cutter will then be case hardened but not through hardened. 
 Jerry, if you make a cutter with a rack form to the teeth you can in fact cut any amount of gear teeth with it. The catch is that as the gear blank is rotated the cutter has to be advanced to follow the circular dimension of the pitch diameter. 
 Bevel gear cutting is not the same as spur gear cutting for the fact that the tooth needs a parallel profile and you can't do this with one pass. To do this the blank needs to be rotated to some degree and then the cutter cuts one side of one tooth. After that pass the blank needs to be rotated to the other side of the tooth, the cutter offset from center and then a second pass is made. 
 And no, it can't be done with a hob.
gbritnell


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## Dan Rowe (Jun 22, 2010)

Bob, 
Many thanks for the reply. I finished the drawings of the Rush gears for the #6 cutter they look like the 18 tooth drawing. I will line weight then and post then soon.

Jerry,
Now you have my interest as bevel gears are my main objective because I am a Shay fan. I think the best type of gear for your project would be a parallel depth bevel gear. They are much simpler to make and the design of them is covered in "Gear Design Simplified" . This is also covered in Ivan Law's gear book as I have read it on the web.

I do not believe a parallel depth bevel gear can be cut with a hob but a normal spur gear cutter can be used so the same method you used to grind your gear cutters with the Rush drawings could be used. Heck one of the ones you already made might work fine. 

I know that a proper bevel gear can not be cut with a hob, a Gleason machine is what is used for modern bevel gears.

Dan


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## Artie (Jun 22, 2010)

Brian, it comes as no surprise to me that the thread has "taken on a life of its own" as you say.

You embarked upon an exercise of learning, you achieved your goals while conceding that there are better ways of producing the goal and that "you probably wouldnt do it this way again"..... I thought your thread was open, clear and honest.

IMO the reason the thread has taken off was simply because of the reaction to your post, less than supportive I would have thought... something you simply dont find here on HMEM... consequently your friends here have taken a little 'umbrage', on your behalf of course.

So please dont be surprised, you are highly regarded here, and deservedly so.

Rob


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## Maryak (Jun 22, 2010)

Jerry,

I agree with George and Dan. ;D

The only way I know to make bevel gears using a milling machine is to make "Parallel" bevel gears using the appropriate DP cutter or your single point flycutter.

Here is a crap 0 cad






As you can see , it takes a minimum of 3 passes to cut a gear, the initial through the centre cut and then the left and right offsets, with the tool passing through the original cut at the minor diameter. One other vital thing is that all calculations for this are done using the smaller or inner diameter.

Hope this helps reveling in beveling. :

Best Regards
Bob


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## Captain Jerry (Jun 22, 2010)

Dan

I just got my new issue of Home Shop Machinist and the cover picture and feature tease says "Shop Made Bevel Gears". The article was a disappointment to me. It was mainly a book review and to get the whole story you must buy "Building the Climax" by Kozo Hiraoka. There was some discussion pitch considerations on bevel gears and a tiny description on bevel gears vs skew bevel gears. There was no discussion at all on tool path and offset. 

It whet my appetite and left me hungry so I have downloaded a solid model of a miter gear from the Rush Gear site and I have read all that I could find re bevel gears on the net. I think that I have worked out the geometry for a tapered height, radius faced, tooth form and the tool path required to cut it with a single point cutter. At least for 90 degree miter gears. I think I can translate the geometry to the 160 degree configuration that I need. When I get to it, I think it will be possible to cut in a single pass. 

The gears will not rotate, they will nutate and be used to prevent rotation in a wobble plate engine. It is not a new idea. It has been used before and only recently came within my ability scope (I hope).

Are you building a Shay? Have you reached the point of cutting the gears? I would like to see it.

Jerry


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## Captain Jerry (Jun 22, 2010)

Bob, 

We were posting at the same time so I got head of your answer. I have seen that recommendation (parallel form) teeth before. And I have seen Gleason machines in operation. From what little I know about Gleason machines, I thought that their primary virtue was cutting curved tooth forms as in spiral bevel gears and hypoid gears.

If that is true, what is the right machine to cut a proper bevel gears, a shaper?

Jerry


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## Dan Rowe (Jun 22, 2010)

Jerry,
I have all the geared engine books by Kozo so the article was interesting to me, but it really requires the Climax book for complete understanding. That gear is a skew parallel depth gear where the two shafts are not in the same plane. The only place I have ever seen detailed information of that type of gear is the Climax book by Kozo.

Nutating bevel gears wow what fun.

There was a method to cut aproximate bevel gears with thin versions of standard spur gear cutters. The cutter curve was set for the big end and was thin enough to pass through the small end. I have seen these cutters on ebay from time to time. The method requires the small ends to be filed to correct the curve error.

I am building a Shay in two scales. I have been writting a series on the 7/8ths scale 10 ton Shay for G1 track in "Steam in the Garden" The prints are 7/8 scale versions of the Lima Locomotive Works drawings. The series started with issue #100 with a double fold of both sides and end views in 7/8ths scale.

I have not cut a bevel gear yet but I hope to soon.

The drawings of the Rush gears for 17, 19 & 20 teeth look very similar to the 18 tooth version. The red tooth profile is the generated profile in the single tooth inset.

The proper name of a gear shaper to generate bevel gears is a Bilgram machine. I have a bit of a collection of information on these machines and can start a thread on them.

Dan


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## Maryak (Jun 22, 2010)

Jerry,

One thing I forgot to answer is yes a hob will cut a gear with any no. of teeth for the given DP/Module. The small ridges formed using the hob are soon worn away as the gear works, but IMHO they are noisier than a gear made with a DP cutter. A bit of heavier oil sorts that out.

Because the tooth form as well as the depth of a "True" bevel gear varies along its' length. A generator such as the Gleason you refer to gives the correct tooth profile. A gear so generated could then be used a the cutting tool on a gear shaper.

Ah what a tangled web we weave.

Best Regards
Bob


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## steamer (Jun 22, 2010)

Kozo published a great way to make bevel gears, spiral bevel gears, and spur gears in the lathe as part of one of his logging locomotives. Home Shop machinist recently republish some of this work.  Even shows, as only Kozo can, how to make the fixtures and gear cutters in your own shop....Worth every penny.

Dave


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## Dan Rowe (Jun 22, 2010)

steamer  said:
			
		

> Kozo published a great way to make spiral bevel gears,
> Dave



Dave,
The Climax gears only look a bit like spiral gears they are actually straight tooth skew bevel gears with 90 degreee shafts not in the same plane. Kozo had to work out how to make this very rare type os bevel gear and that is an apendex to the Climax book. And yes the books are worth every penny. Some of the technique I learned from Kozo I was able to use in full size practice as a Marine Engineer.

Dan


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## steamer (Jun 22, 2010)

Thanks for the response Dan.

Your correct to the terminology...the hour is late and I've been going since 5am

I found a spread sheet on the net that did the Kozo calculations for the bevel gears.

I think it was from the Yahoo gear cutting group.....I'll look.

Steam or Diesel?

Dave

PS Uploaded a Google book on Spur and Bevel Gears.....still looking for the spreadsheet....I know I saw it somewhere...


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## Dan Rowe (Jun 23, 2010)

steamer  said:
			
		

> Steam or Diesel?



Dave
Mostly diesel on low speed Sulzer engines.

Thanks for uploading that book some interesting stuff including the thin bevel cutter method I mentioned and skew bevel gear theory. I checked the publication date and it is 1915 which is a year before the formation of the AGMA (American Gear Manufacturing Association). This is fine by me as all most all the Shay gears were designed before the AGMA so they were not standard gears.

Bilgram's machine is mentioned but no good picture of one of the machines. The machine invented by James Gleason which is what is used today is also mentioned. Template bevel gear planers were perfected in the US by William Gleason the father of James and they are mentioned in the text.

There were machines whose only purpose was to make the templates for template planners. This method was made obsolete by the Bilgram machine (1885) which is essentially an attachment for a shaper to generate bevel gears. James Gleason invented a machine (1905) that uses rotary cutters that are stationary and the gear blank moves that made the slower Bilgram machine obsolete.

Dan


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## Dan Rowe (Jun 23, 2010)

Brian,
I started a thread about the Bilgram bevel gear shaper. 
http://www.homemodelenginemachinist.com/index.php?topic=9759.msg107096

You will see that my first expermental gear did not come out as good as your gear. Sometimes a do-over is required.

Dan


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## Captain Jerry (Jun 23, 2010)

As long as we are posting failures, here's mine:







This is the start of a non-90 degree bevel gear. Cut three spaces, phone rings, deal with it, return to gear making, screw it up. Due to loss of concentration, the blank was advanced in the wrong direction. The cutter crashed into the hardened capscrew holding the blank on the mandrel. The cutting edge was wrecked, the set up moved. I knew I was dead. I would never get the cutter reground and the set up restored. So I started another pass, just to see how bad it was.

If you look closely at the first three passes, you may be able to see tapered teeth, with a pretty good profile on the outer edge. That's a steel blank. I'll try again tomorrow.

Jerry


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