Gear tooth pitch identification - help

[Avadon77]

I'm trying to find out as much information as I can regarding the following inner ring gear on this slewring. I've contacted the seller as well as the manufacturer. Seller knows almost nothing. Manufacturer won't respond to emails. So I'm at a loss. Gear pitch gauges on Amazon are pretty expensive and I'm not even sure which gauge set to get.
The slewring is a 1/14 scale K970 Excavator Model Slewing Bearing.

I'd like to know:
Diametral or Module Pitch ?
Pressure Angle ?

From this calculator:

RC Gear Calculator

RC Gear Calculator - The Metric Module and Diametral Pitch is Calculated by Entering the Outer most Gear Diameter in mm and the Number of teeth on the gear

www.radiocontrolinfo.com

I put 108 into the Gear Outer Diameter (mm)
and 100 into the number of teeth
and I got 1.06 Metric Module and 24 Diametral Pitch
Is this math correct? Is it 24Pitch?

I'm trying to find a mating pinion gear (possibly a gear train) to drive this slewring so I'm trying to find as much about the slewring as possible. Would it be likely to assume a 20dg Pressure Angle on this type of Chinese metric gear?

 

[sfriedberg]

24 DP isn't metric.

With a magnifying glass and a good angular reference (protractor, reticle, etc) you can probably distinguish between 20 and 14.5 degree pressure angles. Those are the two most common, but there's no guarantee it will be either.

The difficulty with reverse engineering gears is that production designers are not compelled to stay with standard sizes and tooth profiles. So there's always a chance this was a product-specific custom gear design that simply does not match anything in a catalog. Fasteners have not been like that for many decades, but you will still find "special" threads in mechanisms even if OEMs don't use specials to hold things together.

As one tiny, tiny example: The gear calculator is based on standard tooth height. But a pretty common variation is stub teeth (height appropriate for a couple DP smaller gear) and it's very very common to make addendum and root modifications on pinions with a small number of teeth, or on the gears the pinions work on.

 

[Peter from Holland]

Design and make the whole thing from scratch Also the mating gears
Peter

 

[EmGo]

Since it's modern chances are real good it's Mod and if so you don't need to worry about pressure angle, pretty much nobody has used 14.5* in the past fifty years.

Go grab a little pinion of a known pitch and roll it with your part. If it rolls smoothly, good enough.

 

[john.k]

Since its for a model ,then its probably a standard pitch ........actual excavator internal rings are special teeth to resist breakage under heavy shock loads.

 

[Avadon77]

24 DP isn't metric.

Could all the measurements be metric and it have an imperial pitch like 24? Is that not the correct pitch? Did I get the calculation wrong?

24 DP isn't metric.

So if all the measurements are metric, it's not "Diametral Pitch," instead it's Module?

 

[Avadon77]

Design and make the whole thing from scratch Also the mating gears
Peter

This is my third option if this slewring doesn't work. I felt that off the shelf will always be easier than scratch building as I don't have a great deal of engineering experience with these rings and driving them. I'm trying to come up to speed. If this setup doesn't work then I will have to model one in solid works and I know of a company who can machine these things. Hopefully I don't have to go that route on this project.

 

[Avadon77]

I found this page.... it's super informative. I'll post it in the hopes that it might help others who find this thread.

Choosing Gears Best Suited for Your Application | ManufacturingTomorrow

Q&A with Ronald Valenzuela, Engineering Manager, KHK Gears: As technology advances, we have seen a shift into using much finer pitch gearing. We have certainly come across more exotic gear designs in the Mechatronics field that require a much smaller design..

www.manufacturingtomorrow.com

What is module and how does it differ from diametral pitch?​

The most popular designator for pitch outside of the U.S. is what is known as module. To determine the value of module for a given gear, you measure the pitch length in millimeters and divide that value by π. For example, if the pitch length measured 9.425mm, this would be a module 3 gear. By incorporating π into the value of pitch, the metric dimensions of a spur gear are very simple to calculate. The pitch diameter of a module 3 spur gear with 25 teeth is equal to the module (3) multiplied by the number of teeth (25), or 75mm. It also simplifies the calculation for addendum, dedendum and whole depth. For a DP gear, the addendum is equal to 1/DP, the dedendum is equal to the whole depth minus the addendum, and the whole depth is equal to 2.157/DP. When dealing with module, the addendum is equal to the module, the dedendum is equal to 1.25 times the module, and the whole depth is equal to 2.25 times the module.

Similar to DP gearing, standardized module values have been established. For course pitch power transmission gearing, the typical values for Module are 10, 8, 6, 5, 4 and 3. For medium pitch fractional horsepower gearing, the values for module are 2.5, 2, 1.5 and 1.25. For fine pitch instrument drive gearing, the typical values are 1, 0.8, 0.7, 0.5, 0.4, 0.3 and 0.2. Within metric gearing the concept of circular pitch (CP) also exists. By subtracting the value of π, CP values of 2.5mm, 5mm, 10mm 15mm and 20mm are common.