Gear cutter and depth of cut

[Wino1442]

Hi all.... I am cutting a 20 tooth 32DP gear for the Hoglet engine. After cutting and looking at it I noticed that the tooth profile didn't look quite right. The top lands were way too narrow and on the first gear I cut the teeth basically came to a point. I've checked and re-check my setup and am satisfied that it is fine. Then I figured I had taken too deep of a cut, which according to the math should be .0704 (using 2.2/P +.002). I double checked the depth of cut with a dial indicator to compare with what the DRO said and they agreed with one another.

On the second gear I made a .068 depth of cut and the tooth profile still did not look correct....I made measurements of wires and appeared to be about .002 too deep still. So, I'm not sure what the problem is...

On the cutter there is a number printed, .1197. which I'm not sure what if anything it refers to.

I have attached photos of the cutter and the second gear for your viewing pleasure.
I'd like to hear your ideas and/or opinions. Thanks

 

[benmychree]

American cutters are marked D+F + the depth, who knows what they do in china. Look up, the figures in Machinery's handbook, and try again.

 

[francist]

According to my copy of Gears and Gear Cutting (Ivan Law) the full tooth depth for a 32DP gear is 0.067” so you’re not far off (from your second try at 0.068)

Edit: thinking a bit more on this as it’s been a while since I cut a gear, I seem to recall my gear cutters having a slight off-centre rotation to them as they cut. Like one side or tooth always seems to cut a bit deeper than another. So, depending on which tooth I set my starting depth from I could be out on the final depth by that small off-centre amount. You know, if I happened to zero on the lowest tooth and then dialed in twenty-thou for depth I’d actually end up deeper than I wanted by a thou or so. Just something to keep in mind if you’re splitting the last thousandth or two trying to hit a depth right on.

-frank

 

[f350ca]

There was a discussion on a forum some time back that the Chinese cutters were numbered backwards. Could you be using the equivalent to a No 3. ??????

Greg

 

[Wino1442]

I know the numbering on these Chinese cutters is an issue. My question is is the cutter number wrong or is the teeth cutting range wrong? So, the cutter I have (the one in the photo) says it's a #6 and Z17-21...is that correct or could it actually be a #3 Z35-54?

 

[f350ca]

The cutter for forming up to a rack a number 1 should have straight teeth, or almost, at the pressure angle of the gear. If its labeled as an 8 then the numbers are backward.

Greg

 

[Wino1442]

Unfortunately I don't have the whole set...just the 2 I needed. The good thing is that the 2 I got are #3 & #6, which if they are in reverse order then I can use the #3 in place of the #6. I'll have to try it...

 

[Wino1442]

I'm also wondering what 0.1197 and the 14 markings are.

 

[Wino1442]

Attached is a photo of a 20 tooth gear I cut using the cutter that has #3 (Z35-54) printed on it. I also used a depth of cut of .674 and after cutting it it looked right. So...I guess the cutter is actually a #6 (Z17-20). Thanks for the replies.

 

[benmychree]

The cutter is marked 17 21 teeth, it is obviously the right cutter for 20 teeth, if it is correctly marked, that begs the question, is it correctly marked?