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Cutting gear teeth....I need the basics

David_M

Hot Rolled
Joined
Sep 30, 2014
Location
Midway, GA, USA
For those that might be curious, this is what EG's 11 tooth on a mod-2, 12-tooth gear blank looks like:

172060642.png
 
Last edited:
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
For those that might be curious, this is what EG's 11 tooth on a mod-2, 12-tooth gear blank looks like:
Thanks very much, David_M. Not too pointy. Looks good.

Oke Now I see
Not much torc then and no chance in a catastrofic failure
Buy the gears then and connect these to a shaft
No chance my ass, undercut teeth are quite happy to break and that head weighs more than 6 ounces. David M very kindly did the hard part, so at this point ya pays yer money and makes yer choice.

Isn't there a saying ? "Do it right, do it once" ?
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
This is the "electronic version" of the Sunderland method
Picky mean-spirited comment :) That's actually hobbing. In a Sunderland (or Maag, who invented it a hundred years earlier) the rack stays stationary while the blank rotates across it.

If you want to go computer crazy, you could emulate the way they do big gears, which is cut one tooth with a single tooth, then back out, retract, and index. Then cut the next one. Pointless but fun for you nerds, maybe :)

If you put a little star or something in the center of the blank, it would be obvious what's happening earlier.

If you made a program that drew unusual tooth shapes ? That would be really useful to some people. PC Gears used to do this but haven't been able to find that guy for decades. It was super helpful for making new gears for oil pumps, where the walls would get scored and you need to clean them up, then make new gears to fit the cavity. Sealing at the tips was the main goal there, and a drawing is the best way to see what's going to happen with oddballs.

Nice job, DM :)

p.s. If you did a 12 toother on the same blank, people could see what we're talking about ?
 
Joined
Jan 15, 2005
Location
The Netherlands
Thanks very much, David_M. Not too pointy. Looks good.


No chance my ass, undercut teeth are quite happy to break and that head weighs more than 6 ounces. David M very kindly did the hard part, so at this point ya pays yer money and makes yer choice.

Isn't there a saying ? "Do it right, do it once" ?

Those blanks are hobbed If it is a standard M2 rack the 12 teeth gear will fittAlso it is a horizontal adjustment Weight is not a issue Peter
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
So the 11 tooth is simply 11 teeth in the space of 12, where the space between teeth is greater? Or the difference is made up elsewhere?


I ordered a 12" piece of pinion wire from McMaster..it'll be here tomorrow. I plan to cut off a piece about 3" long, turn down the end to provide the 'snout' that registers on the far side of the rack, and then attach the whole thing to a longer piece of round rod. I'll try it for fitment.


While I do want this piece to work well, it does not need to be ultra-precise as the rack moves slowly, seldom, and by hand force only. There's no motor involved or repetitive motion. I've actually been able to slide it by pushing on the end with both hands....you basically are overcoming the friction/stiction of the horizontal ram.


If the McMaster piece (12 tooth, 12 pitch) does not work well, I'll dig further into an 11 tooth affair.
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
This is a standard 12 tooth (I used a silhouette of Miss Audrey Hepburn for the star)
Nice choice :)

Could be worse, hunh ? Graphics makes it easy to visualize how bad the situation will be. Are you using commercial software or is this your own code ?

Also, what kind of fish are those ? I kept expecting t see a gator leap into action from the right, and gobble them all up :D
 

52 Ford

Stainless
Joined
May 20, 2021
Nice choice :)

Could be worse, hunh ? Graphics makes it easy to visualize how bad the situation will be. Are you using commercial software or is this your own code ?

Also, what kind of fish are those ? I kept expecting t see a gator leap into action from the right, and gobble them all up :D
That's commercial software. It's "Algodoo" by Algoryx. It's a (free!) 2D physics simulator. Been using it (mostly playing) with it for years.

Excellent tool for animations like this.

It's also multi-touch compatible. My workstation laptop is multi touch and it actually makes for really quick designing and simulation. Not complex stuff, but trying to explain an idea to someone or figuring out linkage ratios. That sort of thing.

Sent by telegraph using - .- .--. .- - .- .-.. -.-
 

David_M

Hot Rolled
Joined
Sep 30, 2014
Location
Midway, GA, USA
Nice choice :)

;)

Could be worse, hunh ? Graphics makes it easy to visualize how bad the situation will be. Are you using commercial software or is this your own code ?

I'm using Rhino 3d with its scripting language. It has been working very well. I'd bet it could do those oil pump gears that you mentioned here:
...for making new gears for oil pumps, where the walls would get scored and you need to clean them up, then make new gears to fit the cavity...

Also, what kind of fish are those ? I kept expecting to see a gator leap into action from the right, and gobble them all up :D

Those are some always hungry flathead catfish. I did have a gator stop in the pond a few years ago, but he moved along, surprisingly, without help. Those gators like your dogs too much.
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi again GregSY:
You wrote:
"I ordered a 12" piece of pinion wire from McMaster..it'll be here tomorrow. I plan to cut off a piece about 3" long, turn down the end to provide the 'snout' that registers on the far side of the rack, and then attach the whole thing to a longer piece of round rod. I'll try it for fitment."

As an alternative, I'd turn down BOTH ends of my pinion wire...one end to the diameter you need in order to fit it into its receptacle, and the other end just enough to clean up the root diameter, leaving the gear width you want in the correct place along the length of the shaft.
I'd then push a sleeve over the one end.
That way you preserve the strength of it and you still get the shape you wanted.
The sleeve can just be pressed on or even fastened with nothing more than Loctite...it will see no stress, and just functions as a bushing, so long as you make the driving handle attach to the shaft protruding out the center of it.
If you want to get really anal, put in a taper pin.
I'll betcha you'll NEVER break it...that remaining shaft will be close to 7/8" diameter.

Solves the problem of atttaching a shaft to one end of the gear.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
Well...The first try at using the pinion wire is a dud. I knew when I ordered it I didn't like the OD of 1.170....I knew it would need to be turned to 28MM, or 1.1" So I tried that, but of course the real issue is the pitch diameter is 1.000" and that's a little too big. So, the teeth need to be more pointy and less wide. They do fit the rack in open air, but not when I try to slide it in the bore.

I'm guessing the correct pitch diameter is a millimeter designation...24 or 25MM....and not the 25.4MM that is 1 inch. If the PD were a little undersized that would be a lot more forgivable than oversized.


I've had little time to spend on this but my next step will be to look for a proper metric-spec gear as others have suggested.


voest gear 12 12 .jpg
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi GregSY:
You really need to find the distance from the pitch plane of the rack to the axis of the pinion.
So the pitch plane is the plane where the rack tooth is the same width as the tooth space.

If you have CAD, it's pretty easy to find...simply draw up the profile of the rack and the distance to the bore from the dimensions you take from it.
You have already established the pressure angle.
Drop a gauge pin into a tooth space on the rack that's big enough to protrude from the top of the rack but small enough that it's sitting between two teeth and is tangent to both flanks.
Measure how far the gauge pin sticks up and record it.
Build up a gauge block stack and a second gauge pin that you can just push in the housing and have it touch the far wall of the bore the pinion goes into and the gauge pin that's between the rack teeth.
Now that you have the key dimensions, get busy making a picture of the rack and the bore in their correct relationship.

Now you can pull the distance from the pitch plane of the rack to the axis of the gear.
You know the pitch circle is supposed to be tangent to the pitch plane (theoretically...not considering clearance).
Now you can construct the main dimensions of the theoretical gear you need and see if there's a stock pinion wire you can buy that is those dimensions.

Note that you don't need the exact pinion tooth form, you just need enough information to pick the right gear.
If you determine it's not a standard, you can always figure out the profile later, but, like you, I'm pretty confident from the bits of information we already have that the PCD of the pinion is 24 mm or maybe 25 mm.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
Yes, I think it is 24MM or even 23MM.

I'll have to dig into it next week when I get more time. Meanwhile, I dug further into the head in hopes of fixing the gear shift. Or, rather I hoped I could access the gears from the back of the head but...I find they have a hard-to-explain complex heavy iron ram within the main ram that covers the back of the head. The precision in this piece is 'high' and I'm still wondering why they made it this way.




Voest ram.jpg
 

52 Ford

Stainless
Joined
May 20, 2021
Well...The first try at using the pinion wire is a dud. I knew when I ordered it I didn't like the OD of 1.170....I knew it would need to be turned to 28MM, or 1.1" So I tried that, but of course the real issue is the pitch diameter is 1.000" and that's a little too big. So, the teeth need to be more pointy and less wide. They do fit the rack in open air, but not when I try to slide it in the bore.

I'm guessing the correct pitch diameter is a millimeter designation...24 or 25MM....and not the 25.4MM that is 1 inch. If the PD were a little undersized that would be a lot more forgivable than oversized.


I've had little time to spend on this but my next step will be to look for a proper metric-spec gear as others have suggested.


View attachment 332783
Is that a 1964 nickel?

Sent by telegraph using - .- .--. .- - .- .-.. -.-
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
That's commercial software. It's "Algodoo" by Algoryx. It's a (free!) 2D physics simulator. Been using it (mostly playing) with it for years.
Downloaded it, didn't work. Once upon a time places would list the basic requirements for software, so you could avoid wasting your time getting it if you knew it wasn't going to work.

I hate software clowns.
 

52 Ford

Stainless
Joined
May 20, 2021
Counterfeit..... Hot off the press, prototype..
That makes sense.

Way less obvious than counterfeiting the big denominations - like quarters.

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