# Gear Cutter, What can you get away with



## Blair (Mar 6, 2020)

Hi everyone, new here and is my first Post
I am looking for gear cutters on ebay I need 6 DP 14-1/2 degree PA Cutters #3,#4, and #6. I am having trouble finding the #6 cutter which is located in USA or Canada because China is now shutdown to exports.
So my Question is, Can I get away with cutting a 20 tooth gear with a #5 cutter which is used to cut 21-25 teeth, the #6 cutter is on the High side 17-20 teeth, so would the gear run ok in my change gear train to cut threads?
Also can you use a 20 degree tooth gear with a 14-1/2 degree tooth in a not so perfect world or situation

Thanks for all your opinions and suggestions
Blair


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## Ulma Doctor (Mar 6, 2020)

if both gears will be cut from the same tool, the point is moot
they will match


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## benmychree (Mar 6, 2020)

I likely have a spare cutter, will look.  If the gears are cut with the same cutter, they may not mesh properly with each other and others in the gear train, they could run rough or noisy in proper mesh.


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## benmychree (Mar 6, 2020)

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


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## Bi11Hudson (Mar 6, 2020)

Good morning, Sir. And welcome aboard. Keep in mind that I am by no means a machinist. I have an electrical background and spent my life keeping the machines running. My knowledge is at a hobby level, not professional. Although I have, and use, a copy of Machinery's Handbook.

With that said, my first suggestion would be to study up on gear cutting, preferably with text instead of videos. Gear cutters "fit" one size correctly, the rest of the span is an "almost right, close enough" fit. If I were facing your particular situation, I would size the gear close to the first number and run some lapping compound for a while instead of oil. But that's me, not professional advice. Further, lapping compound will be "sticky" and you must consider the other gears in the train.

I think the first consideration would be to consider the use for such a gear. Is it a change gear for threading on a lathe, or a transmission gear for an automobile. The lathe gear can be soft, brass or even plastic for a smaller machine. The transmission will have to be tough, will have high torque and carry you away from the ability to quickly repair it. Your call~~~ Would it be practical to print a plastic gear? That opens up a whole 'nuther subject.

The second consideration would be the ability to mesh, specifically the pressure angle. Different pressure angles *DO NOT MESH*. Period. Consider if you would take a 14 DP gear and try to drive a 16 DP gear? That would be sort of like trying to mesh 14-1/2 and 20 degree teeth. I'm sure that if you had the time and enough lapping compound, and didn't mind sharp edges that they could be _made_ to run together. But there *are* practical limits.

In both cases, a possible solution could be found using gear cutters from Russia(?). I have several sets that I'm not too sure where they came from. Some from China, some from Eastern Europe, some from Russia. Search eBay, looking long and hard for your particular size(s). And don't necessarily buy the first set you find. Look for price and availability over some time. I took months to find what I wanted. Some for the reasons given, some because I didn't have the money right away. But I got what I wanted eventually, at less than $100 *per set of 8*. Waiting works wonders~~~

I cut mostly plastics and aluminium so am not too particular about how tough they may be. Your results may (and probably will) vary, depending on material and your patience.

*EDIT (or afterthought)*
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.

Bill Hudson​


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## Blair (Mar 6, 2020)

benmychree said:


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


Please send me an email and ill send you my shipping address
at   bemullen@ns.sympatico.ca
Thanks Blair


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## Blair (Mar 6, 2020)

Thanks to everyone who has given me advice and help

Thanks Blair


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## Blair (Mar 7, 2020)

Bi11Hudson said:


> Good morning, Sir. And welcome aboard. Keep in mind that I am by no means a machinist. I have an electrical background and spent my life keeping the machines running. My knowledge is at a hobby level, not professional. Although I have, and use, a copy of Machinery's Handbook.
> 
> With that said, my first suggestion would be to study up on gear cutting, preferably with text instead of videos. Gear cutters "fit" one size correctly, the rest of the span is an "almost right, close enough" fit. If I were facing your particular situation, I would size the gear close to the first number and run some lapping compound for a while instead of oil. But that's me, not professional advice. Further, lapping compound will be "sticky" and you must consider the other gears in the train.
> 
> ...


When you have a chance check the cutter to see what # it is
About the pressure angle, you compared it to meshing different DP's, but in that case the teeth are different size and pitch so they can't mesh with each other.
I the case of 14-1/2 compared to 20 degree, the 20 has a narrower crown and a wider root, but the pitch of both gears are the same or at least very very close, I would think you should be able to adjust the backlash enough to compensate for it. Another thing I might be able to do if it didn't  adjust close enough because the tooth bottoms out, I could turn the OD down to get my clearance tighter for the narrower 20* tooth.

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

Thanks Blair


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## rgray (Mar 7, 2020)

Blair said:


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



I'll vote "hold out til you get that $20 correct cutter" . That is one hell of a bargain. I thought heck if he doesn't want it I'll buy it.
But then I checked and I already have one.


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## Blair (Mar 7, 2020)

rgray said:


> I'll vote "hold out til you get that $20 correct cutter" . That is one hell of a bargain. I thought heck if he doesn't want it I'll buy it.
> But then I checked and I already have one.


Im going too but I want to understand how it all works and what one can get away with if they have too
the last gear i cut was in vocational school in 1978, got it sitting on a shelf over the living room window


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## brino (Mar 7, 2020)

Blair said:


> Hi everyone, new here and is my first Post



Hi Blair, and welcome to the group!



benmychree said:


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





Bi11Hudson said:


> 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 NumberStandard 
Tooth Range
(from Machinery's Handbook 30th Edition)Tooth Range
(from current ebay offerings; and the latest set I bought from China)1135 to rack12-13255-13414-16335-5417-20426-3421-25521-2526-34617-2035-54714-1555-134812-13135 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


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## Blair (Mar 7, 2020)

brino said:


> Hi Blair, and welcome to the group!
> 
> 
> 
> ...


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


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## jwmelvin (Mar 7, 2020)

Blair said:


> 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.


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## Blair (Mar 8, 2020)

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


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## Lo-Fi (Mar 8, 2020)

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!


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## rock_breaker (Jul 24, 2020)

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


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## john.k (Jul 24, 2020)

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 .


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## Blair (Feb 17, 2021)

brino said:


> Hi Blair, and welcome to the group!
> 
> 
> 
> ...


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

Blair


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## dbb-the-bruce (Feb 25, 2021)

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.


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## brino (Sep 22, 2021)

Blair said:


> 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


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## FOMOGO (Sep 22, 2021)

Welcome to the forum. Pretty sure plastic won't cut it on the 48" Niles. I have a smaller 26" version. Would love to see pics of your 48. Cheers, Mike


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## ErichKeane (Sep 22, 2021)

If you can find the tooth profile in a book, what about grinding a single-point cutter for it?  You'll have to go slower feed rates (since it is only 1 tooth!) but you can grind whatever size you want (then just run it in a fly cutter).


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## Larry$ (Dec 23, 2021)

ErichKeane said:


> you can grind whatever size you want (then just run it in a fly cutter).


I've done that just to see how well it works. I tried both acetal (Delrin) and aluminum. It worked but was slow and I'm sure the profile was not perfect. I tested them as change gears on my 1440 lathe and they seemed to run fine. Short term test! Dividing was done with my 8" rotary table & plates. The catch is the bulk of the table means needing a longer shaft to set the blank up on to clear everything. A BS-0 or BS-1 dividing head would be better. I've actually been considering buying a BS-2 to push the limits of my abilities beyond what I can likely manage. Am I really that crazy?


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## Winegrower (Dec 23, 2021)

Larry$ said:


> I've actually been considering buying a BS-2 to push the limits of my abilities beyond what I can likely manage. Am I really that crazy?


I'm gonna go with NO here.    You need this.


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## Larry$ (Dec 23, 2021)

Winegrower said:


> You need this.


NEED? 
I have no valid use for such a thing. This is just a hobby gone astray. I'd like to hear from anyone that has a BS-2 and has set it up to do helical gears.
Shipping weight is about 145#! SWAG means the head itself is likely in the 90# range. That is the thing that is making me reconsider and just buy a BS-1. No helical gear making, but I can handle that weight.


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## benmychree (Dec 23, 2021)

I have an original B&S #2 and use it routinely, they are not just for spiral milling, but also for differential indexing, and since the worm can be disengaged, can be conveniently used for direct indexing using the plate behind the chuck.  #0 and #1 are more toys than useful tools, at least in my opinion.


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## Larry$ (Dec 23, 2021)

benmychree said:


> #0 and #1 are more toys


All my metal working stuff are toys! 
I have lots of questions about this subject.  
How often do you set it up to do spirals? 
How long does it take to setup for spirals? 
Do you have a lift of some sort?
My mill is a Jet 9 X 49. I think it can handle the weight OK but that weight is going to be all at one end of the table.


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## benmychree (Dec 23, 2021)

I do not do a lot of spiral work, just occasionally, also differential indexing, just when needed for prime number indexing such as 127 for metric transposing gears, yes, I do have a lift, I used a barn door track and a HF electric hoist; I used to lift such things as the dividing head and lathe chucks by hand, back troubles no longer allow suchlike.  The weight at the end of the table is just one of those things that are a necessary thing, in some cases, such as when the dividing head is geared to the table screw, other times it may be placed anywhere on the table that is convenient, like using a vise, it can be located anywhere.  Setting up for spirals is quite easy and can be done quickly, although it might take some extra work to set up on a non Brown & Sharpe machine, which has a couple of drilled and tapped holes on the end of the table to accomodate change gear brackets.  The information on spiral setup is contained in B&S book "Practical Treatise on Milling and Milling Machines" find a copy online or perhaps E Bay, it is a gold mine of info, including spiral work and indexing and lots more.


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## Larry$ (Dec 23, 2021)

benmychree said:


> "Practical Treatise on Milling and Milling Machines"


It's on Google books. I spent some time reading  and skipped though other sections. There were a lot of attachments for a mill I've never seen.
I book marked it. Thanks


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## benmychree (Dec 23, 2021)

Larry$ said:


> It's on Google books. I spent some time reading  and skipped though other sections. There were a lot of attachments for a mill I've never seen.
> I book marked it. Thanks


I'd like one of each of those attachments!, I did pick up the slotting attachment and parts of the rack cutting att. and arbor braces and the short lead and feed reducing att., it had the universal milling att. which serves for vertical milling. also have 2 of the universal vises.


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## Larry$ (Dec 23, 2021)

You've amassed quite a collection. 
I just mostly do thing to prove I can. I also do some repair work mostly on the woodworking shop's equipment. 
I passed on doing one awhile back and shouldn't have. A cast-iron bracket got broken that was part of the lift mechanism for the inside vertical head on a German made molder.  It had a metric ACME type thread and I didn't have a set of taps for it. I had the machine shop down the street make a new part in steel. I told him it was metric but he didn't seem to grasp that part of it. He struggled more than I would have and had to make the part over at least twice.  In the end I had to modify the part to make it work. I prefer to work in metric, easier. Our shop has a mix of domestic, Imperial, and European equipment. Sure wish the US had gone metric back in the 70s when they talked about it. 


benmychree said:


> I did pick up the slotting attachment and


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## benmychree (Dec 23, 2021)

Th





Larry$ said:


> You've amassed quite a collection.
> I just mostly do thing to prove I can. I also do some repair work mostly on the woodworking shop's equipment.
> I passed on doing one awhile back and shouldn't have. A cast-iron bracket got broken that was part of the lift mechanism for the inside vertical head on a German made molder.  It had a metric ACME type thread and I didn't have a set of taps for it. I had the machine shop down the street make a new part in steel. I told him it was metric but he didn't seem to grasp that part of it. He struggled more than I would have and had to make the part over at least twice.  In the end I had to modify the part to make it work. I prefer to work in metric, easier. Our shop has a mix of domestic, Imperial, and European equipment. Sure wish the US had gone metric back in the 70s when they talked about it.


The metric trapezoidial thread, although similar to our acme thread is not at all the same, it has a 30 degree included angle instead of out 29 degree, it is really entirely different. a little homework on the guy's part would have saved the rework.


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## Larry$ (Dec 24, 2021)

A large machine shop that does a lot of work for Goodyear and other manufacturers. Given that a lot of manufacturing equipment is imported, they would have to deal with Metric on a regular basis. When his part failed after a few days we found that it has a ?pressed? brass/ bronze?  threaded bushing  that had slid out. *I don't know if you can rely on a press fit for brass to steel or not*. But in this case the fit was little more than "snug." I put two setscrews through the steel and into pockets on the bushing. Might work? The bushing has a shoulder that supports the primary load but when the shaft is reversed it still might have some load due to breakaway effort and a considerable cantilevered load. 
I suspect the bushing was a purchased item. Even though I'm slow as molasses I could have gotten it done faster and not relied on a sloppy press fit.


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