×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

helical gear question

helical gear question

helical gear question

(OP)
Hello,

Hoping someone could help clear up some confusion for me, or point me in the right direction. I'd been under the impression that for a helical gear, the true involute profile would be located in the transverse plane. However when specifying helical gears, pitch and tooth thickness are often given in the normal plane. Additionally I was under the impression helical gears could be cut with standard hobs, that are set angled from the gear axis, to create the helix angle. This would leave me to believe that the true involute form for helical gears is being made in the normal plane--the plane that is perpendicular to the action of the hob. Is someone able to help explain where I'm going wrong here? Should the true involute form be in the normal or transverse plane?

Thanks in advance.

RE: helical gear question

The true involute form is created in the transverse plane.
To allow using the same hobs for different helix angles (including the 0 angle), gears are almost always specified in the normal plane. One exception is the TCP system, another would be the face milled spiral bevel gears.
In gear hobbing the helix angle is created by the machine kinematics. The hob is set angled to provide proper cutting conditions and correct pitch & rack angle in the transverse plane. The true involute form is created in the transverse plane with transverse pitch and transverse rack angle.

Hope that helps.

RE: helical gear question

(OP)
I guess I may not be fully visualizing how hobs generate the involute form. I don't understand how gears are specified in the normal plane, to use the corresponding hobs, but then those hobs create a true involute form that is not in the normal plane.

RE: helical gear question

As a hob travels through the entire face width of a helical gear, its cutting edges are enveloping a basic rack surface. This basic rack has the same pitch and rack angle as the hob- in the normal plane. In the transverse plane, the pitch and rack angle are slightly different, they depend on the helical angle, but still a basic rack with straight flanks is being formed. This basic rack in the transverse plane is generating a true involute form of the gear.

RE: helical gear question

Spigor is correct and a done well to explain.
I will add this.
The hob has a lead angle so in the hobbing machine the helix angle is obtained by adding the lead angle of the hob plus the lead angle of the helical gear.
the data input is normal dp & PA but because of the helical angle, is calculated to the transverse.
all measurements taken in transverse.

in other words if the helical gear is machined correctly, when inspected the involute, lead and tooth to tooth will be machined correctly.
thus a good gear.

so to reiterate
input is
#T, DP N PA N Helix Angle to obtain the proper gear attributes.

RE: helical gear question

A slight correction
Helix of gear - Helix of hob= x

X+ hob Helix = Helix setting of machine.
To obtain part Helix angle.

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


Resources

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