Duplicating a Gear...?

[tdfsu9]

I have a 88 tooth spur gear (6.190" diameter)and I'm wondering how I can duplicate this gear? I don't have any of the other gear specs. I have access to a CNC mill and a lathe, I just don't know the best way to duplicate this gear without any other gear specs.

Thanks a bunch for any assistance,
Jason.

 

[alexit]

See Identifying unknown gears at:

http://www.gizmology.net/gears.htm

Maybe you can calculate what you don't know...

 

[Philrock]

The scheme at gizmology is good only if the gear is not profile shifted. It does not work for profile shifted gears, even if you swear at it, as pointed on their website. In fact, for certain profile shifts, it can give you a flat-out wrong answer.

A more reliable way is measurement over pins. If you don't know the pressure angle, you may (not positive about this) have to take measurements using 2 different sizes of pins. Then you have to do lots of math. For reference books for the math see thread 406-146377.

Another possibility is caliper measurements over several teeth, and, again, lots of math.

 

[Carburize]

Gear repair shops are now beginning to use sophisticated CMM machines to get the required data, eliminating the need for measurements over pins.

 

[gearman1234]

The softwares to measure unknown gear data are very costly.
I use the measurement over pins, no. of teeth, OD, Root dia, Base tangent length to arrive at a preliminary data. Using this preliminary data and making assumptions based on this data, I use Klingelnerg gear checker to check the profile and lead of the gear. By making calculations based on this data I arrive at a final data.

 

[multiproducts]

We are suspicious of the pressure angle of several of our gears we get from suppliers. Documentation has been lost, etc. What is the best way to measure the pressure angle of a gear. We have an optical comparator but not a CMM. I can line up what I think is the angle on the comparator but got values like 16 deg. when it should be 14.5 or 20 deg.

 

[israelkk]

multiproducts

This is not a good idea to start a new post inside an other post. You already started a second new post.

 

[gearcutter]

As a gear cutter I am required to identify unknown gear types every day with out the use of CMMs, Profile projectors etc.
The first place to start is by measuring the base pitch of the sample. This is done with a good set of verniers and measured tangentially in the normal plane over a certain number of teeth. The number of teeth over which to measure is worked out by laying the jaws of the verniers over the "best fitting" number of teeth". By this I mean the number of teeth that allow the jaws to contact the tooth profile somewhere around the pitch line (about half way down the profile from the tip of the tooth) and not allow the tips of the jaws to make contact in the root area nor have them make contact right up on the tips of the teeth. Then take the next best fitting measurement either side of that; so if the first measurement was made across 10 teeth then take a measurement over 9 or 11 teeth, which ever fits best. Subtract the smaller measurement from the larger and what you have is the base pitch.
Let me know what you measure and I’ll let you know what to do next.

 

[spigor]

There's no simple answer to this question. Generally you should start with a simple way, like caliper or wire measurements, trying to match your gear to standards and if that fails go to a higher level. But some designers don't want this "reverse engineering" and try to make it as hard as possible. I'm doing it for years and you would hardly believe what I have seen. If you can't make it then find somebody with a lot of experience, that's what I think.

 

[dimjim]

Is the 6.19 the od or the pitch diameter?
If it is the od, it looks like a 1.75 module
gear to me. I would start with the most
common 20 degree pressure angle and see
how it compares.