cutting a gear

[Flopearedmule]

I have a question....
I want to cut a 50 tooth gear with a single tooth gear rack cutter. I drew it on CAD and it doesn't look like I thought it would. Do I have something wrong with my math? The DP is 8, so the circular pitch would be .3927
If I cut in the center of my 6.25 diameter part mounted in my indexer. Cut a depth of .270 all the way around the part.
then raise my knee up .3927 (circular pitch) then cut all the way around again. Then lower my knee .3927(circular pitch) and cut all the way around again. I should get close enough with the profile
in the picture the green is the center cut with the single rack cutter on a 6.25 Diameter. The white is the knee lowered and raised the circular pitch. It looks like it is not cutting in the right location. Do I have my math wrong?
Here is a link to what I am trying to do...
http://www.jeffree.co.uk/pages/multi-tooth-gear-cutter.htm

This method was also in issue#40 of Strictly IC

I need some help, I can't figure it out. It looks like the circular pitch is too much, and cutting on the wrong side of the tooth.
Thanks

 

[Cogsy]

So you've made a single tooth cutter rather than the rack type in your link? I'm a little confused I think, but I have a link to another resource for making/using rack cutters if you're interested : LINK . I've made them with success in the past and the single pass method appeals more to me than multiple passes at different heights.

 

[Flopearedmule]

So you've made a single tooth cutter rather than the rack type in your link? I'm a little confused I think, but I have a link to another resource for making/using rack cutters if you're interested : LINK . I've made them with success in the past and the single pass method appeals more to me than multiple passes at different heights.

I bought a cutter for $30, and I only need it to cut a couple gears. I thought spend little more time with the indexer vs making a cutter and heat treat it. Thanks for the link.
I figured out my problem. I went to bed and thinking about it as I was going to sleep, and it hit me. It is supposed to be a 48 tooth with a 6.25 diameter. I wasn't subtracting the 2 in the formula. Now back to bed, and I will fix the CAD drawing in the morning.

 

[Flopearedmule]

OK, I redrew the ACAD drawing and now it looks much better. Green is the rack profile and white is the gear. tooth profile.jpg

 

[Mechanicboy]

I think this explain much better how the gear vs rack is created.. The milling tool as "rack" to cut the gear in right tooth profile either it's 25 teeth gear or 100 teeth gear.

[ame="https://www.youtube.com/watch?v=2I4Yp_B-qbg"]https://www.youtube.com/watch?v=2I4Yp_B-qbg[/ame]

And you can read this link how to create own gear cutter..

http://www.helicron.net/workshop/gearcutting/gear_cutter/

 

[MachineTom]

Recheck your diameter, a 50 tooth gear 8DP needs 6.5 Diameter blank. 50 + 2/8=6.5"

 

[Flopearedmule]

Recheck your diameter, a 50 tooth gear 8DP needs 6.5 Diameter blank. 50 + 2/8=6.5"

Thanks. read post #3 and #4. I eventually figured that out.

 

[Flopearedmule]

Almost looking good! Now I will have to chuck it in the lathe and turn all the teeth off to make a 12 DP with 66 teeth. This is what happened when I didn't measure twice and cut once. I have 50 teeth on a 6.25 diameter wheel, (8 DP) Dammit!!
I didn't notice until I cranked my knee up the .393 circular pitch, and it was cutting on the wrong spot.

IMG_4177.jpg

 

[Cogsy]

Oh well, it was good practice... if you get the time, especially for smaller sizes like I.C. timing gears and the like, I recommend you have a go at making a cutter as per the link Jens and I gave, it's quite simple and the results are very good. I have used mystery metal and also drill rod for the cutter, heat treated with a hand help map torch and tempered in the kitchen oven (don't tell my wife :hDe.
Good luck with the next attempt!

 

[Flopearedmule]

Oh well, it was good practice... if you get the time, especially for smaller sizes like I.C. timing gears and the like, I recommend you have a go at making a cutter as per the link Jens and I gave, it's quite simple and the results are very good. I have used mystery metal and also drill rod for the cutter, heat treated with a hand help map torch and tempered in the kitchen oven (don't tell my wife :hDe.
Good luck with the next attempt!

Thanks, I thought about doing it that way, but for $30 I can buy an involute #1 cutter (135 to rack). these teeth are bigger, and cutter will only be used one time. So I chose the faster route. I might make a smaller gear and use some A2 to make a cutter another time... We will see.
Here is a quick sketch what I am making. Sausage Stuffer with 3 speed transmission. I had 48 teeth figured and the last min before making the gear I double check my dimensions and forgot to add the plus 2 in the formula.(some cuss words might have been said when I finally figured it out). I will be changing the first and second gear to 12DP, 66 teeth, so I can still use my blank(just need to turn the teeth off). It will get me .118 linear in the rack for every turn. It was .203 for every turn with the bigger 8DP 48tooth, so maybe my screw up will be better in the long run. My 3 year old daughter might be able to turn it for me now that it will be easier.
The big 58 tooth gear will be 1.5" wide and made with some 7075 aluminum I had laying around, and the pinion will be a solid piece of 4140 with 10 teeth. If the 7075 don't take the force, I might have to make the big gear out of steel.
FullSizeRender.jpg

 

[Mechanicboy]

Thanks, I thought about doing it that way, but for $30 I can buy an involute #1 cutter (135 to rack). these teeth are bigger, and cutter will only be used one time.

Also move the gear cutter #1 from center to other side measured in chordal pitch iwhere the length of chordal pitch is measured with dial indicator after the first round of cutting the gear wheel is done then cut the gear wheel to create envolvent on the teeth in second round and then the third round in the other side of teeth.

 

[Flopearedmule]

Also move the gear cutter #1 from center to other side measured in chordal pitch iwhere the length of chordal pitch is measured with dial indicator after the first round of cutting the gear wheel is done then cut the gear wheel to create envolvent on the teeth in second round and then the third round in the other side of teeth.

That is the plan. That is when I discovered I had the wrong tooth number.

 

[Mechanicboy]

That is the plan. That is when I discovered I had the wrong tooth number.

Yes, it is quick to make mistakes without checking that indexing is correct before work can begin.

 

[Flopearedmule]

If anyone is interested, I was always wondering about turning a super spacer into a dividing head with the plates, crank handle, and sector. I bought this kit on ebay....mounted on my 6" super spacer, and it works great! I have better stability. The only thing I don't like is the 90:1.......I would rather have 40:1

 

[Mechanicboy]

I has Soba indexing table with 90/1. Your indexing head with 90/1 indexing and you need 50 teeth to cut in gear wheel --> 90/50 --> 1 turn and 16 hole in 20 hole plate.

 

[Cogsy]

Jens, I don't think it's the math that is the issue, it's turning the handle 90 times to get the workpiece to turn once!

I know I get sick of counting turns with my 40:1 dividing head so I can see where you're coming from. It's the main reason I'm considering converting it to run on Arduino as so many others have done.

 

[Mechanicboy]

Jens, I don't think it's the math that is the issue, it's turning the handle 90 times to get the workpiece to turn once!

I know I get sick of counting turns with my 40:1 dividing head so I can see where you're coming from. It's the main reason I'm considering converting it to run on Arduino as so many others have done.

Ah, so clearly, thanks.

 

[Flopearedmule]

Jens, I don't think it's the math that is the issue, it's turning the handle 90 times to get the workpiece to turn once!

I know I get sick of counting turns with my 40:1 dividing head so I can see where you're coming from. It's the main reason I'm considering converting it to run on Arduino as so many others have done.

Thanks Al, yes that is the issue with me, 90 turns. I don't use it to much so not too big an issue.

I just started playing with Arduino, is there some links you can point me?? To see other projects?
I have a archery string jig/winder I am building and using Mach3 right now. (I have these steppers going almost 1,500RPM's). I have a friend that is helping me so I can use Arduino instead of my laptop. I should get variable speed with the Arduino also.

 

[Cogsy]

I just started playing with Arduino, is there some links you can point me?? To see other projects?

There are a couple of options commonly in use for rotary tables. The first is Chuck Fellow's version LINK which has been used with great success and I believe quite simple. Then there's RodW's very powerful version: thread documenting the development LINK (very long thread) or simplified installation instruction thread LINK.

I'm about to start the search for hardware at a cost I can afford, then I'll make the decision as to which way I'm going to go. I've also got a couple of Raspberry Pi projects promised to the kids (including a retro video game console/emulator) so there's a bit of electronic work coming my way in the near future.

Finally, here's a video showing Rod's software in operation - the user had his microstepping configured incorrectly in this video, which is why the divisions are a bit off, but once he fixed that it worked perfectly.

[ame]https://www.youtube.com/watch?v=thxf7Uw0q2Y&feature=youtu.be[/ame]

 

[Flopearedmule]

The gears are on hold for now. I have almost completed my String Jig.
Here is a youtube video simulating 2" of serving. It works great with Mach3. Someday maybe I'll get excited about the Arduino(I have someone looking into it for me from the Archery club)
I need to put controls in a box and get compressed air in my basement, and I will be ready to make some strings.

[ame]https://www.youtube.com/watch?v=9gaDqluuhhY[/ame]