Involute Gear Cutter Question

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.

Problem was the one I brought was only sold as 20 DP, 14,5 PA, #5. Can't see a tooth count on the cutter from the picture provided but it does appear to have 'Detroit' written on it so I'm now expecting it to be 21 to 25 teeth - not actually what I wanted.
 
If you go by the picture, yes the #7 looks like it will cut 14 to 16 Teeth. It looks heavy whereas the #8 in that picture looks lighter at the cutting edge. The only way to really tell is to have one in my hands and that won't happen in my lifetime. I wouldn't touch mismarked tooling with a 10 ft. pole. I also won't buy imported cutters either, been burnt before. The seller of those cutters appears to know squat about the standard or he would have caught that obvious mistake.

"Billy G"
 
Last edited by a moderator:
Glade I didn't buy them then. The one that I have ordered may not actually be the one I currently need but at least it does appear to be American made.
Not a problem, I'm not opposed to having excess tooling on hand just in case I find I need for it in the future.
 
The gear set in the original picture appears to be for the US diametrical pitch system. The #1 cutter also appears to be smaller than the #8 cutter. It is appropriate that the higher tooth count cutter be smaller, so the gears are marked correctly for the cutter standard they were made to. The problem a lot of North Americans have in these situations is that they do not take into account that the rest of the world works in metric. The metric module standard numbers their cutters in reverse order and they IIRC they also cut different numbers of teeth per cutter than the diametrical pitch system. Using Ebay as a reference is iffy at best because someone ignorant of how the two systems work can come to incorrect conclusions.

Personally, I would not buy a cutter without the full set of markings, including cutter number and number of teeth cut.
 
The #1 and the #8 cutters are side by side in that picture. The #1 says it cuts 12 to 13 teeth, #8 says it cuts 135 to rack. That is just the opposite of what it should be so please, take a moment to tell me how they are marked right. I listed the correct numbers, those on the cutters clearly do not match.
"Billy G"
 
Last edited by a moderator:
CONCLUSION --- Both numbering systems are correct. The ones in the first picture are Module. They number them backwards so as not to get them mixed up with DP cutters.


"Billy G"
 
I have to agree with what others have posted about imperial involute sets from China. I recently bought a "China" set of cutters, 14-1/2 degree 16 pitch. In my opinion they are marked backwards, they are direct opposite from what my Machinery's Handbook list how they should be marked and other very old American made set of cutters.
 
As I stated, they are marked opposite on purpose, they are Module not DP. To mark them the same would be a fatal mistake. Module will not cut DP gears and vice versa. A #1 in DP cuts 136 to rack. A 31 in Module cuts 12 & 13 teeth.

"Billy G"
 
Last edited by a moderator:
As I stated, they are marked opposite on purpose, they are Module not DP. To mark them the same would be a fatal mistake. Module will not cut DP gears and vice versa. A #1 in DP cuts 136 to rack. A 31 in Module cuts 12 & 13 teeth.

"Billy G"

Billy,
My cutters are marked 16 DP 14.5° pressure angle. Am I mistaken, I thought Module cutters are to cut metric gears not imperial
 
Yes, you are correct, module cutters cut metric gears. That's why the numbers are backwards so they are not confused.

"Billy G"
 
Back
Top