Root dia. tolerance as per B92.1 1996

[spigor]

Hi
I'm trying to find out the root dia. tolerance for the folowing spline:
Flat root side fit B92.1 1996
DP6/12
14 Teeth
30 PA
Internal

I've found in the standard, that the root dia. is 2.562, but have had difficulties to find its tolerance. Is it 2000/P+130=.0463?

Any help would be much appreciated.

 

[gearcutter]

My info tells me for flat root side fit B92.1 1996:
Internal Maj dia = 2.5583" +0.0040



Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[tbuelna]

spigor,

As far as I know ANSI B92.1-1996 does not provide tolerances for root diameters (ie. internal spline major diameter and external spline minor diameter) of 30deg PA, flat root, side fit splines. The spec only provides a single limit dimension for each. Table 9-30 lists a value of 2.562" MAX for your internal spline major diameter, and a value of 2.094" MIN for your external spline minor diameter. With this type of spline the root diameter tolerances are generally not a concern, so they are not specified.

The only other dimensional control over root diameter limits for this type of spline is provided by the form clearance calculation shown in table 2. The basic radial form clearance (cf) is .001D, with a max limit of .010" and a min limit of .002". The radial form clearances take into account the combined tolerance stack-ups for root fillets and external major diameter/internal minor diameters.

The equation you show from table 107 (Do=2000/P+130) is only for the (-) tolerance value of the external spline major diameter. If you really need to determine the minimum limit for the root (major) diameter of your internal spline, you can get a close approximation by adding twice the max fillet radius of the internal spline to the max major diameter of the external spline.

Hope that helps.
Terry

 

[spigor]

I assume the simplest way to get the root dia. w/tolerance is to use the formula (N+1.35)/P (page 4, thanks lbmakem), which gives 2.558 to determine one limit, and the second limit 2.562 is shown in the table. This is also in line with what gearcutter says.

Thank you for your support and the very useful information,
spigor

 

[tbuelna]

spigor-

As i noted in my previous post, the upper limit for the major diameter of your internal spline is 2.562". The lower limit of the major diameter of your internal spline is equal to the sum of twice the root fillet radius of the internal spline (we'll use a .020"R for this example), twice the cf (2 x .001D = .0046"), and the max OD of the external spline (2.500"), which works out to 2.5446". This is just an example. To determine the actual value you will need to establish what size root fillet radius will be used for your internal spline.

Hope that helps.
Terry

 

[spigor]

tbuelna,

in case of shaping there's no radius, but a trochoid. Should not the TIF dia. be used instead?
Even if there's a radius (broaching?), I suspect the TIF dia. is not simply equal to the sum mentioned because of the local profile angle.
It seems to be way too complicated for a simple spline.

 

[tbuelna]

spigor,

You are correct, the approach I gave for calculating the lower limit for your internal spline root diameter is an approximation due to effects like local profile angle at the point of tangency. But it should be close enough for your purposes.

I've attached the relevant table from the ANSI spec (table 2). As I noted above, the ANSI spec does not control the lower limit for your internal spline root diameter. They leave it up to you to determine what it should be based on the size/shape of your root fillet. Ultimately, what matters with your side fit spline is that the extreme outer edge of the external tooth flanks do not contact the internal tooth flank surfaces where the root fillet transition begins, since this will result in a large local stress concentration.

If you feel you cannot control the shape and size of your internal spline root fillets sufficiently to prevent this condition, you can always specify a controlled dimension tip chamfer/radius on the external spline teeth to provide some additional clearance margin.

Hope that helps.
Terry

 

[mfgenggear]

Guys

a flat root spline should be .005 max radii.
make sure there is a Go spline plug gage.to accept & verify the parts.

standard cutters will achieve the correct root diameter. the gage will verify two items.
The correct size & the the parts will assemble with no interference with the mating part.
Terry answer is an approximation. but good enough. don't make this harder than it needs to be.
You have a max diameter + it must clear the TIF. period.

talk to scott at Ash Gear to get set up with the correct cutters.

HTH

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.