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Testing Radius of gears

Testing Radius of gears

Testing Radius of gears

(OP)
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

ruso,
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

(OP)
Diamondjim,

   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

Ruso,
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
od.

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

Ruso

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:
http://members.rogers.com/webgear/home.htm

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