Involute Gear Cutter Question

MozamPete

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When I look a references to involute gear cutter set they always refer to eight cutter to cover the range of sizes, and normally list them from a #1 being 135 teeth to a rack to #8 being 12-13 teeth.

When I look at the gear cutter sets out of China on ebay they number them the other way around (#1 being 12-13 teeth to #8 being 135 teeth to a rack ).

Involute-Gear-Cutters-DP20_zpsf6db5c44.jpg

What is the convention? Is this an English vs American difference or a Module vs DP difference?

Immediate reason is I wanted to cut a 33 and a 34 tooth gear so ordered a #5, but now I'm not sure if what is going to arrive is for 21 to 25 teeth or for 26 to 34 teeth.

As a secondary question how important is it to use the correct cutter? Can you get away with using the cutter number above or below in a pinch?

Involute-Gear-Cutters-DP20_zpsf6db5c44.jpg
 
Well, I've bought several different made in USA brands over the years all using the same numbering system...

What do you think the chances are of all the USA manufactures being wrong and China being right :)
 
Buy them by the numbers, DP, pressure angle and tooth range that they will produce, the tools in the picture are well marked (until used) , for instance the tool in the lower right corner is marked , 20 DP, 14 1/2 Deg. PA, 55-134. What could be simpler than that? Naming conventions are meaningless if there is no governing body to enforce them.
 
One last time, those cutters are marked wrong. The ones in the pic will not cut the teeth as marked. They are marked bass akwards. Below is the correct marking for Involute Cutters.

#1 = 135 to Rack Teeth
#2= 55 to 134 Teeth
#3 = 35 to 54 Teeth
#4 = 26 to 34 Teeth
#5 = 21 to 25 Teeth
#6 = 17 to 20 Teeth
#7 = 14 to 16 Teeth
#8 = 12 to 13 Teeth

"Billy G"
 
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Listen to Bill, they are numbered backwards.

If you look at them closely, they are marked correctly for the range of number of teeth they will cut. But are not numbered correctly.

the gear cutter for cutting 12 to 13 teeth is marked as a number 1 cutter. Should be marked number 8. And so on.
 
This seems to be a common problem with the gear cutters coming from China. Every set that I looked at on eBay had them backwards.
 
Those Chinese numbers are backwards. Try to cut 134 teeth with that #7 and you will find out in a real hurry.

"Billy G"

So are you saying looking at the cutters in the picture the number appears correct but the tooth range is incorrect? i.e the #7 in the picture looks more like a 14-16 tooth cutter than a 55 to 134 cutter?
 
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