Spur Gear 9 teeth 3

[mrr1671]

Hi,
I have some problems trying to determine and finding information regarding the right dimensions for this spur gear:
N=9
P=20
Pressure Angle=20

The diameter over wires using 0.096" wires is specified 0.6159"-0.6144"
depth of cut is 0.1120.

I was trying to review if this data is okay but couldn't find it.

According to the formulae for the OD=(N+2)/P =0.55", but the teeth are machined over a 0.590" shaft diameter.

Where or how can I check if these are the right dimensions?

Any help will be great...thanks.

 

[israelkk]

This gear probably has a tooth modification or as called tooth profile shift to avoid undercut. They may even used a larger profile shift than just needed to avoid undercut.

 

[mrr1671]

Thanks for your information,
Do you know where can I get more information on these types of gears?

 

[diamondjim]

Your pinion is cut on an enlarged
center distance. I calculate a
normal pin reading of .58786 with
a standard tooth thickness.

For a 50 percent long addendum,
the reading would be .61734 which
is close to what you have. The
difference is that some backlash
is cut into the pinion.
The od for this would be (N+3)/20
which would equal .6000 for the od.
To avoid excessive undercutting this
makes sense that they would use a
long addendum pinion. I assume the
pinion tip is almost pointed.

 

[mrr1671]

Diamondjim,
thank you for your help.
Yes the tip is almost pointed, as you described.
Do you know which will be the formulae or how to calculate the tooth thickness and the diameter over wires?.

 

[gearcutter]

Here is a link that will calculate what you require

http://www.zakgear.com/Over_Pins.html

 

[israelkk]

Gearcutter:

I looked at

http://www.zakgear.com/Over_Pins.html

and I didn't find the option to calculate gears with a profile shift.

mrr1671:

15 years ago I was in the same situation as you. I had to deal with a corrected (profile shift) gear. I have seen it as an opportunity to dig into the field of gearing. I recommend that you should grab this opportunity to learn the field of gearing as deep as you can.

There are many excellent books that you can start with. Such as the books from Dudley Darle, buckingham, AGMA standards, SDP catalogs etc.

 

[israelkk]

Gearcutter:

Sorry for my previous post, I looked again at

http://www.zakgear.com/Over_Pins.html

and I found the option to calculate over pin dimension for gears with a profile shift. It has the option to enter the "Normal arc tooth thickness on pitch diameter".Therefore, if the enlarged normal arc tooth thickness on pitch diameter is calculated due to profile shift and entered in this table the calculator will calculate the over pin dimension.

 

[diamondjim]

Use the standard dimension over pin
calculations except that the tooth
thickness for a 50 percent long addendum
would be 1.934766/20(Dimetral Pitch)
equals .096738. I hope this helps.

 

[diamondjim]

You can use the calculation that gear
cutter recommended and input the following
tooth thicknesses to arrive at the
pin dimensions you have.
.09572 and .09477 tooth thickness values.