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Working Depth and Whole Depth of Metric Helical Gears 2
- Thread starter Tigerdawg
- Start date
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1
- #2
The formula above means, that the root DIAMETER is 2.25*m smaller than the pitch diameter.
Root RADIUS is half of that value, it means it is 1.125*m smaller than pitch radius. The meshing tooth' addendum = module, subtracting the addendum we'll get the clearance (0.125*m)
Of course, we are still talking about the standard ("N") teeth on both meshing gears; the pitch diameters (z*m) are tangent (they are operating diameters as well).
(the symbols in formulas above mean: z = # of teeth, m = module)
Root RADIUS is half of that value, it means it is 1.125*m smaller than pitch radius. The meshing tooth' addendum = module, subtracting the addendum we'll get the clearance (0.125*m)
Of course, we are still talking about the standard ("N") teeth on both meshing gears; the pitch diameters (z*m) are tangent (they are operating diameters as well).
(the symbols in formulas above mean: z = # of teeth, m = module)
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1
- #5
diamondjim
Mechanical
The dedendum is 1.25 and the addendum is
1.00 so .25 is the clearance. You do not
divide the 2.25 ratio by 2.
Philrock is correct about this.
There are also two ways of cutting helicals
in Europe so caution is needed.
If a rack cutter as Gearguru suggests is
used then the above applies.
1.00 so .25 is the clearance. You do not
divide the 2.25 ratio by 2.
Philrock is correct about this.
There are also two ways of cutting helicals
in Europe so caution is needed.
If a rack cutter as Gearguru suggests is
used then the above applies.
Diamondjim,
If dedendum is 1.25*m (depends on the rack) then
root diameter = pitch diameter - 2.50*module.
In such case I agree that the clearance is 0.25*module.
But in my example above the root dia = pitch dia - 2.25*m,
I calculated with the rack with 1.125*m addendum. For my example the clearance is 0.125*m.
The original question was "What is the rule of thumb for the root diameter", I answered it and calculated the clearance using that answer.
You did not mention that in your case the root dia is pitch diameter - 2.50*module
If dedendum is 1.25*m (depends on the rack) then
root diameter = pitch diameter - 2.50*module.
In such case I agree that the clearance is 0.25*module.
But in my example above the root dia = pitch dia - 2.25*m,
I calculated with the rack with 1.125*m addendum. For my example the clearance is 0.125*m.
The original question was "What is the rule of thumb for the root diameter", I answered it and calculated the clearance using that answer.
You did not mention that in your case the root dia is pitch diameter - 2.50*module
diamondjim
Mechanical
Gearguru,
Well I did read that too quickly.
Most module gearing was 1.166 times
the module until the last 8 years
where 1.25 times the module was adopted
for full depth gears. I have not seen
1.125 times the module on a rack so I
made the wrong assumption. Sorry!
Well I did read that too quickly.
Most module gearing was 1.166 times
the module until the last 8 years
where 1.25 times the module was adopted
for full depth gears. I have not seen
1.125 times the module on a rack so I
made the wrong assumption. Sorry!
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