# Imported Involute Gear Cutter Sets



## Bill Gruby (Feb 6, 2017)

If you buy Imported involute cutter sets, look close at the numbers. Most sets I looked at today and marked in reverse order. This can ruin your day in a heartbeat. PLEASE look before you buy. The number cutter and tooth number should be;

#1 --- 135 to rack
#2 --- 55 to 134
#3 --- 35 to 54
#4 --- 26 to 34
#5 --- 21 to 25
#6 --- 17 to 20
#7 --- 14 to 16
#8 --- 12 to 13

 Again, be aware the some sets at just flat WRONG. The above cutter  number and number of teeth it can cut is written in stone people, don't get bitten. Let the buyer beware.

 "Billy G"


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## royesses (Feb 6, 2017)

My set are backwards ie #1 shows 12-13. I looked that up on the web and it seems they say that all the china made cutters are backwards. They number them opposite to American standards. I'm glad you reminded me. Thanx

Roy


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## Okapi (Feb 6, 2017)

Hi Bill,
On many old sets I've seen the two versions of numerotation, sometimes from differents countries of origin, here the increasing numbers system is used on module mills but not on clockmaking tools...


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## Bill Gruby (Feb 6, 2017)

I wish we could get that changed. I know of three guys in the last week that got burnt. Our member Brian building the 5 cylinder radial was one of them.

 "Billy G"


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## Bill Gruby (Feb 6, 2017)

I probably have 50 or 60 cutters here. All are marked as I posted them above. I also have some for a dedicated number of teeth which are specially ground to a certain pitch and that's the only tooth count they will cut. Most of my cutters are Morse or Pratt & Whitney. I for one will not buy imported.

 "Billy G"


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## willthedancer (Feb 7, 2017)

The cutters made in Poland are pretty good, and properly marked. China..... well, you just never know what they made them out of. Could be recycled daihatsus or something, and you have noted the numbering systems.


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## Bill Gruby (Feb 8, 2017)

Gears that are 14.5 os 20 degree pitch angle use the cutters I posted. To cut metric (module0 gears you use the cutters that are in reverse order. You cannot interchange these cutters as pitch angle and module are two different animals.

 "Billy G"


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## willthedancer (Feb 8, 2017)

Bill Gruby said:


> Gears that are 14.5 os 20 degree pitch angle use the cutters I posted. To cut metric (module0 gears you use the cutters that are in reverse order. You cannot interchange these cutters as pitch angle and module are two different animals.
> 
> "Billy G"



Thank you for clearing that up. I have never seen range cutters for mod gears. We always rented a hob or shaper cutter.


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## Bill Gruby (Feb 8, 2017)

I did a lot of research on the reverse order cutters, I thought at first they were a mistake. Not so, they are marked that way purposely so as not to mix mod with pitch angle.

 "Billy G"


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## Bill Gruby (Feb 11, 2017)

I have researched this issue and have a definitive answer. The difference is Metric and English. The number of teeth remains the same. English is Pitch Angle. Metric is Module. They are two completely different animals. Those Cutter sets on Ebay and elsewhere that we thought were numbered wrong are correctly numbered for Module. They are numbered opposite for tooth count so that you do not pick up the wrong cutter.  Hope this clears up the mess.
 If there are any other questions on this just ask and I will try to answer them.

English;
#1 -  135 to rack
#2 -  55 to 134
#3 -  35 to 54
#4 -  26 to 34
#5 -  21 to 25
#6 -  17 to 20
#7 -  14 t0 16
#8 -  12 to 13

Metric;
#1 -  12 to 13
#2 -  14 to 16
#3 -   17 to 20
#4 -  21 to 25
#5 -  26 to 34
#6 -  35 to 54
#7 -  55 to 134
#8 -  135 to rack

 "Billy G"


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## mws (Feb 12, 2017)

So if I were to ignore the cutter's series #, and just abide by the diametric pitch range they should cut, I'd be safe? Or did they screw up that tooth count too?


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## Bill Gruby (Feb 12, 2017)

Why would you want to ignore the series numbers? They are correct as I posted them. If you pick up a #3 and it says 35 to 54 teeth you have a pressure angle, usually 14.5,* (English) cutter. If you pick up a #3 cutter and it says 17 to 20 teeth you have a module (metric) cutter. They numbered them that way so you would not make the mistake.

Diametral pitch, is the number of teeth divided by the pitch diameter. It changes from gear size to gear size. A guess on my part would say yes you can, but I would rather use the numbering system. Just my opinion.

There are only two commonly used pressure angles, one is 14.5* the other is 20* with 14.5* being the most common.

 "Billy G"


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## British Steel (Feb 13, 2017)

Thanks gents, interesting thread because... I'm looking for inexpensive 16 dp 20* pa gear cutters, here in the UK I can find 20* module and 16 dp 14.5*, but not what I'm looking for... I'd be delighted if anyone can point me in the right direction!

Dave H. (the other one)


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## MozamPete (Feb 13, 2017)

Bill Gruby said:


> English is Pitch Angle. Metric is Module. They are two completely different animals.



Not really completely different - just different units measuring the same basic quantity, like feet vs metres.

Module = 24.5/DP

so as I understand it a 20 DP gear cutter would be identical to a Module 1.225 cutter of the same pressure angle (if you could get one).

Now by convention there are certain DPs and Module (and pressure angles) that are in common use, and in that regard the normally available imperial/DP cutters and the metric/Module cutters are different.


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## Bill Gruby (Feb 13, 2017)

The bottom line -- we were trying to find out why the cutters are numbered backwards, we succeeded. By renumbering the cutters the way they did, they have  differentiated between Metric and English.

 "Billy G"


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## mws (Feb 13, 2017)

Sorry. Re-reading your previous post cleared up my question.  So, they were NOT numbered incorrectly, but still, the method of differentiating Metric from English was still nebulous enough to bite a few people.  Thanks for bringing that to our attention.


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## NCjeeper (Feb 17, 2017)

Thanks Bill. I almost screwed up and order a metric set. You saved me some grief.


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## mickri (Feb 17, 2017)

I am just a newbe at this so I could be way off base here.   Involute gear cutters interest me because I need to make some gears for my projects.  I plan on buying a set of involute gear cutters. 
  After reading all the posts and then researching the difference between DP (imperial) and MODULE (metric) I don't think that you can be as simplistic as just looking at the numbering sequence.  In the perfect world DP No.1 is 135  and MODULE No.1 is 12-13.  Based on my research not everybody follows this convention.  I found a company in Australia that numbers both DP and MODULE with No. 1 being 135.  http://www.millerstooling.com.au/Cutting-Tools-Gearcutters-and-Hobs.asp.   And after reviewing a dozen or so EBay listing it appears that all involute gear cutters from China and some Eastern European countries, whether DP or MODULE,  No.1 is always 12-13.  Based on this I think that you really need to go by what is marked on the actual cutter and not whether it is a No. 1 or No. 5 or whatever cutter.  That is what I intend to do.


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## Bill Gruby (Feb 17, 2017)

Your thinking is no different than any here. All we are saying is do not cut one gear DP and the meshing gear Module. This will cause problems. It's that simple.
The numbering system of that Australian Company is awesome. They mark them either DP or M and use the same order. They are the first I have seen do this. Kudos to them.

 "Billy G"


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## mickri (Feb 17, 2017)

Hi Billy,
All of the gears that I saw were marked  with No.,  DP, pressure angle and tooth range or No., Module, pressure angle and tooth range.  I didn't see anything with just the number and tooth range.  When I get around to buying I will go by DP and pressure angle.
Chuck


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## Bill Gruby (Feb 18, 2017)

You have done well Chuck. As a newbie you took nothing for granted. You read what we had to say, researched on your own and came up with a solution that fits your need. I believe you need not call yourself a newbie any longer. You have the process down pat. Congratulations.

 "Billy G"


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## mickri (Feb 18, 2017)

Billy,
You are too kind.  I can look things up and figure things out.  But I don't know squat about actually running the lathe and mill/drill I recently purchased.  That will only come with hands on experience.  The guys who have been doing this for years would laugh their backside off watching me futz around.
Chuck


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## Bill Gruby (Feb 18, 2017)

Not on this Forum, we would lend some help and show you just how much you thought you didn't know. Back in my early days I felt the way you do. One of my earliest mentors told me this. Bill, you have looked at that lathe for 20 minutes now, put the stock in it and turn it on. Once you turn that switch you have done all the damage you can for now. That stuck in my head and the rest is history. Go for it.

 "The other Billy G'  LOL


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## BRIAN (Feb 18, 2017)

Thank you Bill for following up on this problem. 
I have been laid low with a particularly nasty virus for over a week so have been out of the loop so to speak.
The company that i got my original cutter from now has new stock but is still  advertising both DP and Module cutter's
with the same numbering system . I have contacted them today and told them your findings ( not naming you ) I await there reply.
Brian.


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## Silverbullet (Feb 18, 2017)

It's very confusing. I have a gear I need to fix and make one of . It's 34 tooth 10 DP and 14.5 . Which cutter should I look for ? Some cutters I see have just the tooth count and the 14.5 angle but no diametral pitch ? The metric I get with module s there all 20 DP.


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## Bill Gruby (Feb 18, 2017)

All you need is the pressure angle (14.5*) and the number of teeth (34). You will need a #4 cutter. (English) If you wish to figure more info, Machinery's Handbook Edition (26) has all the formulas on page 2004.  Other Editions will be close to that page. Just look up Spur Gear Formulas in the index of the Edition you have. I used 26 because it's the one at my computer.

 "Billy G"


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## Bill Gruby (Feb 19, 2017)

I found only one cutter on ebay with those numbers but again it is in module. #4 10 DP 21-25 teeth is a metric cutter. If it were me and I had this problem the first thing I would invest in would be two sets of gear pitch gages, one DP and one module. Then you would know for sure what you need.  I am by no means an expert on this subject. We had one but he left some time ago. Eric was the best I know on this subject as he did it for a living.

 "Billy G"


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## Reeltor (Feb 19, 2017)

With the gear pitch gages costing an arm and a leg,( it took me months to find one that was affordable) since you have the broken gear you can match it to drawings of full size gear pitches listed in Machinery's Handbook.  In the 11th edition 3rd printing it is on page 700.  If you don't have a Machinery's Handbook you can go to Rush Gear or a similar web provider of gears and use the gear calculator to work backwards to get the proper DP.  Go to RushGears.com and click on custom gear builder.  Enter the Number of Teeth and various Pitches until you get the Outside Diameter of the gear that matches the one that you have in-hand.
If you purchase a gear pitch gauge, some are 14-1/2 pressure angle only, while others are both 14-1/2 and 20 pressure angles.  I've only made one gear so far but the gear pitch gauge has come in handy a number of times.


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## Bill Gruby (Feb 19, 2017)

With all precision gages comes a price. A set of Fowler gages will come with a price tag of $190.00 0r higher. Almost always it will go over $200.00. Unless of coarse you go imported. The price will at times go below $100.00. India or China will be the choices.

A good Gear Tooth Vernier will also help, but again they come at a price.

If you have a handbook with thumb tabs go to the gearing section the full size profiles will be there.

 "Billy G"


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## Reeltor (Feb 19, 2017)

What Billy G said is correct, I searched eBay and finally found a Boston Gear set of gauges for $49.00.  On Boston Gear's site they have 14-1/2 and 20 PA on one set but the one that I bought is 14-1/2 PA only.  I don't know if the set came this way from the manufacturer or if the seller split the set.  (if you search for a used set be sure to search for "gauges" and "gages" )


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## Bill Gruby (Feb 19, 2017)

I had forgotten the spelling difference. I just did a quick search using gear tooth gauges and the price difference is just WOW. Thanks for giving the heads up on that.

 "Billy G"


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## Reeltor (Feb 19, 2017)

Bill Gruby said:


> I had forgotten the spelling difference. I just did a quick search using gear tooth gauges and the price difference is just WOW. Thanks for giving the heads up on that.
> 
> "Billy G"



You are very welcome, Which spelling had the less expensive gear cutters?


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## Bill Gruby (Feb 19, 2017)

Gauge.


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## Reeltor (Feb 19, 2017)

BRIAN said:


> Thank you Bill for following up on this problem.
> I have been laid low with a particularly nasty virus for over a week so have been out of the loop so to speak.
> The company that i got my original cutter from now has new stock but is still  advertising both DP and Module cutter's
> with the same numbering system . I have contacted them today and told them your findings ( not naming you ) I await there reply.
> ...



Brian, I went to the RDG website, do you know where the involute gear cutters are manufactured?  They are listed as having a 1" bore, everything I see from China has a 22mm bore.  I "know" very little about the numbering system between Metric and Imperial other than unless you are purchasing a full set you need to be doubly sure that you are getting the correct cutter to cut the teeth that you need.

Mike


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## Silverbullet (Feb 19, 2017)

I have an old gear gauge it's a free one from a gear company. Not metal but accurate enough to show me the gear I have is the 10 DP with the 14-5 angle , then I counted the teeth 34 cked the count three times too. Still some of the old gear cutters only tell the count and the angle . No hurry tho I still need to find a dividing head and tailstock. Used they sell for more then the China or India clones new with everything.


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## Bill Gruby (Feb 19, 2017)

Just scored a Touch Down. Starrett #456AZ Gear Tooth Vernier --- #110.00 shipping included.

 "Billy G"


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## Reeltor (Feb 19, 2017)

Bill Gruby said:


> Just scored a Touch Down. Starrett #456AZ Gear Tooth Vernier --- #110.00 shipping included.
> 
> "Billy G"



More like a pick-six!  Great buy!!!!!
don't you just love Starrett tools?

Mike


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## BRIAN (Feb 26, 2017)

Hi Mike I am still waiting for a reply from RGD I assume that their DP cutters are ok but am still wary
of the module ones.
The cutter I now have is from China, It is marked in reverse and states the number of teeth it will cut.
But it has a 22 mm bore so I have had to modify the arbour so it now takes both sizes
I have cut a test gear in plastic that looks good. so I am hoping to get into the shop soon to cut the six gears
required for the Radial engine.
Brian.


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## Bill Gruby (Feb 26, 2017)

Brian;

 You will be OK as long as the gears that you are meshing with are module. The tooth profile is slightly different between module and DP. 

 "Billy G"


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## Reeltor (Feb 26, 2017)

Brian,

I just sent and email to RDG Tools asking the country of origin for the gear cutters as well as if they ship to the U.S.
It appears that their gear cutters, both imperial (DP) and metric (module) are numbered the same.  #1 cutter is for 135 to Rack, same as the DP cutter set.  The only listed difference that I noticed, is that the DP sets are 1" bore while the Module sets are 22 mm bore.

http://www.rdgtools.co.uk/acatalog/WHICH-CUTTER-FOR-WHICH-TEETH-2026.html

good luck with your gear cutting.  One problem that I had when running the dividing head to the next tooth location is accidently knocking the sector arms out of position.  What I do now, is to rub some soapstone along the sector arm to mark the correct hole on the dividing plate.  This way if the arm moves out of position it is a simple matter to find the correct hole and reset the arms.


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## Bill Gruby (Feb 26, 2017)

RDG Tools is taking the bull by the horns and correcting the problem of marking. If the cutter is module it is marked as such. Same for DP. Kudos to RDG Tools.

 "Billy G"


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## KBeitz (Nov 18, 2018)

Many years ago I fixed my metric tool problem by spraying every metric tool I had RED....


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## Larry42 (Feb 8, 2019)

"The tooth profile is slightly different between module and DP. "
For a change gear, does the difference matter? They turn slow. 
I've got a Chinese lathe, Module or DP?


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