Gear Cutter, What can you get away with

[brino]

Hi everyone, new here and is my first Post

Hi Blair, and welcome to the group!

do have an extra 6 DP, 14 1/2 PA, #6 cutter available. How about $20 plus shipping?

BTW, I do have a 6DP14-1/2* gear cutter but don't know which number it is. I don't use gears that big so never checked. 1 inch mandrel, it came on the mill when I bought it. You're welcome to it if it would help.

I guess you have already seen first hand how friendly and helpful our membership can be!

Although I cannot directly answer your question on whether the 20 tooth gear can be cut with a #5 cutter, I can offer two things:

1) a warning; be careful with trying to specify the cutter by cutter number only!
It seems that North America and Asia have an inverted sense of cutter number vs. tooth count!

Cutter Number	Standard Tooth Range (from Machinery's Handbook 30th Edition)	Tooth Range (from current ebay offerings; and the latest set I bought from China)
1	135 to rack	12-13
2	55-134	14-16
3	35-54	17-20
4	26-34	21-25
5	21-25	26-34
6	17-20	35-54
7	14-15	55-134
8	12-13	135 to rack

2) an offer;
Plastic change gears are used by many new lathes.
If you would like to try a 3D printed plastic gear I could make one for you.
If you give me the full gear specs, I could print one (in PLA, ABS or Nylon) and send it to you.
All I ask for is an honest, detailed review of the gear here on this site.
Use it for a while and let us all know how well it holds up....or doesn't hold up and we'll try a different plastic!

That kind of review would be useful.

-brino

 

[Blair]

Hi Blair, and welcome to the group!





I guess you have already seen first hand how friendly and helpful our membership can be!

Although I cannot directly answer your question on whether the 20 tooth gear can be cut with a #5 cutter, I can offer two things:

1) a warning; be careful with trying to specify the cutter by cutter number only!
It seems that North America and Asia have an inverted sense of cutter number vs. tooth count!

Cutter Number	Standard Tooth Range (from Machinery's Handbook 30th Edition)	Tooth Range (from current ebay offerings; and the latest set I bought from China)
1	135 to rack	12-13
2	55-134	14-16
3	35-54	17-20
4	26-34	21-25
5	21-25	26-34
6	17-20	35-54
7	14-15	55-134
8	12-13	135 to rack

2) an offer;
Plastic change gears are used by many new lathes.
If you would like to try a 3D printed plastic gear I could make one for you.
If you give me the full gear specs, I could print one (in PLA, ABS or Nylon) and send it to you.
All I ask for is an honest, detailed review of the gear here on this site.
Use it for a while and let us all know how well it holds up....or doesn't hold up and we'll try a different plastic!

That kind of review would be useful.

-brino

I’m all for trying a plastic gear, but here is my situation
I have a large 1960’s 48” Niles lathe which has only imperial threading capabilities
I need a compound gear 6 DP with 37/47 teeth, 1-3/4 bore with a 3/8” keyway, 1-1/2 wide. That’s just for starters. It is my metric transposing gear
Then I need 7 more gears made to give me the capability to cut 2.00 mm to 6.00 mm
1- 20T
1- 28T
2- 32T
1- 36T The only change gear I have (cast)
1- 40T
1- 44T
1- 48T
To buy these gears, I gotta quote of $3500.00
Which is why I need the 3 cutters to machine my own gears
I’m not sure if you’re plastic gears would be strong enough, I don’t know what force would be on the gears
What’s your opinion, do you think they would hold up

 

[jwmelvin]

Am I right or am I way off base with this thinking

I’ve been thinking this whole while that, yes, there is a big difference between a gear train that won’t spin and one that does so with a little sliding contact. Mismatched DP is the former while mismatched contact angle is the latter.

 

[Blair]

I found this cutter on ebay
NOS CANADIAN 3" INVOLUTE FELLOWS STUB GEAR CUTTER 6/8 D.P., 20 Deg. PA, #2 (b)

Can some one explain what the 6/8 DP means? Is it a 6 or is it a 8 DP?

Thanks Blair

 

[Lo-Fi]

Load on change gears isn't huge, so you'd probably get away with plastic - certainly the ones closer to the spindle. Ali gears would hold up perfectly well enough too and they're also nice and easy to cut. I've made some out of Meehanite cast iron, which is lovely to machine but messy.

Cutting with the wrong cutter for the tooth count isn't going to go well.

Diametral pitch cutters are almost always 14.5° PA. Metric cutters being 20° PA and use the module system, not DP. I'd suggest that mis-advertised one way or another!

 

[rock_breaker]

I am currently making an indexer used to cut gears but have never cut a gear. Ivan Law has written a book "Gears and Gear Cutting" in the Workshop Practice Series #17 published by Special Interest Model Books that I believe explains a lot about the subject.
It does seem to me the different shapes even in the same pitch angle are there to reduce rubbing of the gear teeth thus reduce noise and vibration.
Good luck in your project.
Ray

 

[john.k]

You ask about 6/8 DP...this is a stub tooth,often used in (older) truck gearboxes where second gear was a sliding (crash) gear in 6/8DP,20%PA.....To mesh 20 and 14 1/2 gears,they must be in very loose mesh ,lots of backlash ,and low speed ....It can work in a situation where the gears are used for indexing some process.....if looking for 6DP 20 PA gears ,first place would be my collection of old gearboxes....cutting such a coarse pitch on a small mill will take a long time .

 

[Blair]

Hi Blair, and welcome to the group!





I guess you have already seen first hand how friendly and helpful our membership can be!

Although I cannot directly answer your question on whether the 20 tooth gear can be cut with a #5 cutter, I can offer two things:

1) a warning; be careful with trying to specify the cutter by cutter number only!
It seems that North America and Asia have an inverted sense of cutter number vs. tooth count!

Cutter Number	Standard Tooth Range (from Machinery's Handbook 30th Edition)	Tooth Range (from current ebay offerings; and the latest set I bought from China)
1	135 to rack	12-13
2	55-134	14-16
3	35-54	17-20
4	26-34	21-25
5	21-25	26-34
6	17-20	35-54
7	14-15	55-134
8	12-13	135 to rack

2) an offer;
Plastic change gears are used by many new lathes.
If you would like to try a 3D printed plastic gear I could make one for you.
If you give me the full gear specs, I could print one (in PLA, ABS or Nylon) and send it to you.
All I ask for is an honest, detailed review of the gear here on this site.
Use it for a while and let us all know how well it holds up....or doesn't hold up and we'll try a different plastic!

That kind of review would be useful.

-brino

You interested in making some change gears for my Parkson universal dividing head

Blair

 

[dbb-the-bruce]

Consider using CNC to cut one-off gears. If you know someone or have access to a machine it would be a pretty easy job to setup.
I have used my desktop CNC machine to cut gears that I don't have the correct cutter for. It's a Nomad 883 and would work fine cutting brass or AL gears.

You could pick up a new one for less than the price you were quoted for the gear set (Ha!)

Just a thought if you have access to a CNC machine. Someone with a full scale machine could knock out the gears in short order.

 

[brino]

You interested in making some change gears for my Parkson universal dividing head

Sorry Blair, I just saw your question today!

I can still help you out.....but, how many gears are we talking about?
I would need full specs:
-diametral pitch
-pressure angle
-tooth count
-thickness
-centre hole size

Using the above info I can generate the model in Fusion-360 and then print them.
Generating the models only takes a few minutes, printing I usually let run overnight.

-brino