Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Testing Radius of gears

Testing Radius of gears

Testing Radius of gears

Can anyone tell me what a testing radius is for a spur gear??? And how do I calculate that??  What affects it? I know that pitch radius is equal to testing radius in an unmodified gear.

Any website that I can go to calculate over wire dims as well?????

RE: Testing Radius of gears

Go to www.drgears.com there is a range of free software and I think you will find something to help in your over pins dimension calculation.

RE: Testing Radius of gears

Are you talking about doing a wear test
and using the approximated radius of the
gear at the pitch line.  If so it is
basically a line from the pitchline
tangent to the base diameter or
ie the tangent of the pressure angle
time the pitch diameter.  Is this what
you mean?

RE: Testing Radius of gears


   I don't know how to answer you, since I don't know what is a testing radius.  The way it's being used around my new job is to test how good the gear is.  It's used to establish the limits when the gear is rolled.  Basically, Total composite and tooth to tooth error must fall within the max and min testing radius.
   I'm not to familiar with gears, and can't find much on what testing radii are.

RE: Testing Radius of gears

I think from what you described they are
talking about total composite runout check.
From your first description, it sounds like operating
pitch radius with a rack.
If this is the case that they are talking about operating
or running pitch radius with a rack. If the tooth is
thicker at the pitch line, the cutter is withheld a given
amount and the radius would be the pitch radius plus the
amount that the cutter was withheld.  Conversely if cut
deeper you would subtract from the radius the amount that
the cutter penetrated deeper to cut the tooth.  Often
the od of the blank is oversize or undersize by twice this
amount, so it may be enough info if you just check
the od of the part and see how it varies from the standard

RE: Testing Radius of gears

RUSO,  The test radius of a gear is the an old call out. It is the dimension used to set up a double flank checker (at tight mesh) for tooth-to-tooth and total composite checking with a master gear. The test radius of the gear would have a high and low limit based on how much backlash was required. The test radius dimension is basically for checking the tooth thickness.  With a standard gear with no backlash the test radius would be the same as half of the pitch dia.. The amount of backlash and center distance will affect the dimension. A dimension for a measurement over wires will accomplish the same thing as calling out a test radius for the gear (checking the tooth thickness).  If you want to fax me the data for the gears and center distance I could calculate the measurement over wires for you. I do not know of a wed site you could use for this.
Gary, Fax (714)792-2870

RE: Testing Radius of gears


Test radius is an excellent way to quickly measure the quality of a gear.

Test radius takes into account the allowable variation in tooth thickness, and the effect of composite error.  It is also influenced by the number of teeth and tooth thickness of the master although few people are aware of that.

Test radius is a more stringent measurment than just composite error because it takes into acount size and eccentricity.  Therefore if you are looking for a method to better control your gears, Test Radius may be an answer.

There is some debate over the calculating procedure.  The debate has to do with how the composite error is applied to the calculation.

I use software from Web Gear Services - their web site is:

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
Research Report - Simulation-Driven Design for SOLIDWORKS Users
In this engineering.com research report, we discuss the rising role of simulation and the paradigm shift commonly called the democratization of simulation. In particular, we focus on how SOLIDWORKS users can take advantage of simulation-driven design through two analysis tools: SOLIDWORKS Simulation and 3DEXPERIENCE WORKS. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close