# Gears and Gear Cutting on the Milling Machine?



## HMF

Hey Guys,

This is a *LOT* to ask, but I address it to those of you with experience making GEARS on your manual milling machines using a dividing head.

Is there anyone out there willing to do a photo-essay on how to make a stud gear, or other replacement gear for your lathe using a manual milling machine?

I know it is a lot to ask, but it really would be helpful to us newbies.

Thanks in advance,


Nelson


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## Joe in Oz

Have a look at this video. Should shouw you all you wanted to know: 
[video=youtube;VHTXaU7GZC0]http://www.youtube.com/watch?v=VHTXaU7GZC0[/video]


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## toolingjim

chengdave2003 link=topic=1598.msg9576#msg9576 date=1302439733 said:
			
		

> I've got a lot of new-to-me terminology to learn. And I need to start looking for some of those cutters...
> 
> Dave


If you find a cheap source for gear cutters, especially 14 1/2 degree pressure angle, please let us know. These cutters have gotten expensive the last few years. Oh, and be careful with buying on ebay. Some of the sellers there think anything round with teeth on it is a 'valuable gearcutter'.


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## 8ntsane

Gear cutting, Ive only done it twice. I will in the near future be making up a few gears for my American lathe. Starting with a 127 tooth gear, I will be making up a few differant tooth counts. Im determaned to cut metric threads on my lathe.

I will be using a rotary table as thats what I have. Not going out looking for a dividing head just for this job. I plan on giving this a go when the weather is a bit warmer here.

Im hoping the out come is good, but whats better than making the parts for your own machine. Im going to use 
Marv Klotz,s rotary table program, used it before, worked out well.

Ill be keeping my eye on this thread, just incase there is any major (gear heads ) in here. ;D

Paul


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## toolingjim

I've done gears using my home built rotary table turned vertical. You have to figure out a tailstock support and a way to eliminate play between the gear arbor and the rotary table. The tailstock from my 6" Atlas lathe worked well for me. The setup is very similar to the one in the Youtube video.
I wrote a spreadsheet to give me the degrees for each position. My table was graduated in decimal degrees, so the spreadsheet was to two decimal places. With it I made the two gears (37 & 47) that can substitute for the 127 tooth gear in my Logan lathe. This combo gives metric thread accuracy to within .02% of true metric. 
I have found that larger diameter gears can be most easily made using plate stock. For the 7/16" wide gears for the Logan, I sawed out rounds of 1/2" CRS plate, drilled and reamed a center hole, and faced and turned it to size on an arbor. The same arbor was used to hold the blank while milling the teeth out. For some larger gears you may need to take two passes, or rough out the teeth with a slitting saw before finishing with the gear cutter.
I learned about gears BI (before internet), but I have found the book Gears and Gearcutting by Ivan Law to be a good and relatively inexpensive introduction to the subject. You may have to do a bit of translation from English to American, but it does a good job of explaining the basics, as well as showing you some good home shop machinist type tricks.


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## wawoodman

toolingjim link=topic=1598.msg10639#msg10639 date=1302921975 said:
			
		

> chengdave2003 link=topic=1598.msg9576#msg9576 date=1302439733 said:
> 
> 
> 
> 
> I've got a lot of new-to-me terminology to learn. And I need to start looking for some of those cutters...
> 
> Dave
> 
> 
> 
> If you find a cheap source for gear cutters, especially 14 1/2 degree pressure angle, please let us know. These cutters have gotten expensive the last few years. Oh, and be careful with buying on ebay. Some of the sellers there think anything round with teeth on it is a 'valuable gearcutter'.
Click to expand...


I don't know what would be considered expensive, but this outfit has them http://www.victornet.com/cgi-bin/victor/alphabetic/Gear-Cutters-14-1-2-deg-11-DP-to-18-DP/1188.html
There are 3 other pages, with more sizes.


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## 8ntsane

Jim/ Mike

Thanks for the input
I have a 12 inch rotary table V/H, and will be mounting a 4-jaw chuck on it to hold a arbour I will make up. I will most likly have to have a key way in the arbour and gear blank to hold it steady while the machining is going on. I do have a very stout
tailstock to hold the other end of the arbour, so thats no problem.

Im still doing alot of reading about diametrial pitch DP and pressure angles PA . I know there is other tooth counts that sub the 127 tooth. The thing I still have to sort out is the DP for this. The DP on a 127 tooth will apparently dictate the OD of the gear. The OD still needs to fit inside the cover on my machine. My Manual gives me all the infro for the stock end gearing including the tooth counts, DP and PA , but when it comes to the input for the Metric conversions gears ,it doesnt give the DP and PA, just the tooth counts..

The manual even goes as far to give me all the different stud gear counts, and the threading charts as to set up for all the metric pitches. So Im trying to keep it that way, as the factory has allready figured it out. It will be nice to just go to the chart, and look up what set-up, get it set, and cut my choosin metric thread., just a few more things to sort out, before I get into this. The only other gears Ive done where to reproduce a couple of spur gear that had a few teeth knocked off them. That was easy in comparison to what Im attempting to do now. :

Paul 8)


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## toolingjim

8ntsane link=topic=1598.msg10872#msg10872 date=1303087052 said:
			
		

> Jim/ Mike
> 
> Thanks for the input
> I have a 12 inch rotary table V/H, and will be mounting a 4-jaw chuck on it to hold a arbour I will make up. I will most likly have to have a key way in the arbour and gear blank to hold it steady while the machining is going on. I do have a very stout
> tailstock to hold the other end of the arbour, so thats no problem.
> 
> Im still doing alot of reading about diametrial pitch DP and pressure angles PA . I know there is other tooth counts that sub the 127 tooth. The thing I still have to sort out is the DP for this. The DP on a 127 tooth will apparently dictate the OD of the gear. The OD still needs to fit inside the cover on my machine. My Manual gives me all the infro for the stock end gearing including the tooth counts, DP and PA , but when it comes to the input for the Metric conversions gears ,it doesnt give the DP and PA, just the tooth counts..
> 
> The manual even goes as far to give me all the different stud gear counts, and the threading charts as to set up for all the metric pitches. So Im trying to keep it that way, as the factory has allready figured it out. It will be nice to just go to the chart, and look up what set-up, get it set, and cut my choosin metric thread., just a few more things to sort out, before I get into this. The only other gears Ive done where to reproduce a couple of spur gear that had a few teeth knocked off them. That was easy in comparison to what Im attempting to do now. :
> 
> Paul 8)



For what you're doing, the most important thing is to find out the DP and PA of the gear(s) you will be connecting to. Your gears must be the same DP and PA. The book I mentioned as well as Machinery's Handbook contain all of the formulae you will need after that. Do your best work. While geartrains on a lathe have some leeway for adustment, care in manufacture will give quieter, smoother running gears.


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## CharlieW

I recently made some gears for a 10" Logan QC gear box.

I found this link informative.

http://www.engineersedge.com/gear_menu.shtml

This has a great explanation on gear geometry.

http://helicron.net/workshop/gearcutting/involute/

Charlie W.


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## 8ntsane

Charlie/ Jim

Thanks for the links, They all help in my learning curve.
I know that all the gears in the end gearing are 12DP 20o PA
But , I have the manual, and it shows a 127t/ 60t gear. Now to use that DP , the 127t gear will end up 10.750 Diameter.
That is not going fit in the end cover. I can get a 7.5 to 8 inch in that spot max.

I do know that some other lathes use a different DP on the metric converion gears, but Im in the middle of try ing to figure out what Sidney put in these machines. They did change it , and that bracket that swings as well. I thought that bracket would be slotted behind the gears that are bolted to it, nope, no slots in that thing, ecept for the two ends for back lash ajust ment. So my search goes on.

Thanks guys
Paul


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## CharlieW

Paul,
A 12 DP is a pretty big tooth profile. I think your teeth may be smaller than 12DP. The Logan QC I made gears for recently, had 20DP, 20 degree PA gears in it. The change gears on the end were 18DP. I have this 1880's Prentise Brothers lathe that has a few broken teeth in one of the back gears which is a fairly coarse tooth gear and it is a 14 DP.

I determined the DP size with a gear pitch gage.






I forgot to mention that I used an 8" rotary table mounted on edge of my Bridgeport. I placed a #3MT arbor in the center hole in the R-table and held it tight with a draw bolt. The arbor had a 1/2-20 thread extending from it. I stacked my gear blanks on it and tightened the nut on the end of the arbor to hold the blanks. I had no keyway to hold the blanks.


Charlie W.


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## 8ntsane

Hi Charlie

I have the manual for the lathe that covers the 14 & 16 inch swing lathe and the 18 to 20 swing. According to the manual, it is 12 DP and 20o PA . This manual isnt the run of the mill owners manual. This is more of a service type manual, thats gives the complete tear down of the complete machine. This includes all gear tooth counts DP & PA for all gears. This thing gives all part #s for all bearings as well, its pretty detailed except the metric gearing. They show the drawings of the metric gear train , with tooth counts, and set up. They didnt go into detail about DP & PA like the rest of the lathe.

Sidney Lathes of that yr could be ordered with the full metric gearing, and all the screws where in mm metric as well. The drawing for the metric version was totally different as well.

Now being you had mentioned the gear pitch gage, I called around today, and found a company local to me that said they could easy tell me what I have. So, Im going to bring them in a gear , and he said with in a few mins, they could tell me exactly what I have. I did go to that site that you posted a link for. Apparently the formula is (tooth count plus-2, divided by DP) will give the diameter of the gear. I did that test on the gears , and it comes up 12 DP. If I calculate in for any other DPs, the diameter of the gears change. So, Im going to have the gear makers have a look, and see what they say. I suspect the gears are 12DP, and they had a different DP for the metric gear train.
This is a heavy duty machine, so I can figure the manuals infro being right. Even the 18-20 inch Sidney Lathe had the same DP.

Here is a pic of the lathe










Thanks fo the infro given, the links have helped 

Paul


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## CharlieW

Wow, that is quite a lathe. I'm glad I didn't have to move it. Looks like a great machine.


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## GK1918

what a sweety, even better look at his floor. I should have had two girls instead of boys.!


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## 8ntsane

Well, its official
I had the gear checked today, and the gears are 12 DP, and a 20oPA. So I guess the manual is correct. I did show the guy the page from the factory drawing, and he looked at it for a few mins, and said the coversion gears for metric, can,t be 12DP , He said the 60T gear that connects to the 48T gear box gear would have to be 12 DP, but the 127T, the idler, and the stud gear are no doubt a different DP. He did say its going to be a bit of futzin around to figure out what DP the metric conversion gears are, but doable if I spent the time.

So now Ive got to figure out what will fit calulating DP & tooth counts to figure out the diameters, and just what will fit inside the cover. Oh man, this sounds like a slow painfull process. He did say to figure out the diameters for a few different DPs, and cut out the sizes in card board, and slip them over that shafts. It should give me what will go, and what wont. I suppose thats what im doing this weekend.

Huge
Do you think a rotary table would be accurate enough to cut a 127t gear? I know my dividing plates dont show anything pas 99 divs.

The search for the mystery DP continues.
Thanks to all the replys guys, it all helps

Paul


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## 8ntsane

Hugh
Thanks for the reponse.
I will send out a copy of the manual tomorrow, and I will get some pics of gear train with the cover opened up. I will get it all to you tomorrow. 

Yes the metric conversion was factory option, They also sold the same machine with all metric screw, and dials too. The manual will make that all clear.

Thanks Paul


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## toolingjim

I know this thread is old, but I haven't been on here for awhile and as a previous advise-thrower-outer was wondering how the gear cutting is coming along for some of the posters. 

8ntinsane, did you ever get your metric gears sorted out? Was bytewise able to help you work out your gear train?

I have seen some gear trains that changed gear pitches by having gears with two different pitches compounded together on a common keyed shaft. This allowed one part of the gear train to be one pitch, and the rest to be another. Perhaps this is what they did on your lathe. It is also true that the 127 tooth metric conversion gear often did not fit under the guarding on some lathes. Yours might have been one of these.

BTW, I have found that it actually is practical to cut gears with a rotary table, just slow and requiring concentration and a lot of calculating. On the flip side, many dividing heads made nowadays do not seem to have the index plates to do a full set of divisions. The old Brown and Sharpe dividing heads and their Chinese clones could do virtually any divisions you wanted, but really require you to pay attention to what you are doing.

So, any news on the gear front?


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## benmychree

Fact is that you cannot accuratly cut a 127 tooth gear with a normal dividing head or rotary table; 127 is a "prime" number and cannot be evenly divided by any factoring; a universal dividing head is used, where the spindle is geared to the dividing plate, so that while you turn the crank, the dividing plate also turns an corrects for the lack of theoretically correct hole circle. It is called differential indexing. This I did many years ago when I made metric transposing gears for my lathe; I first made a 127 T that fit my automatic gear cutter, as it took a finer pitch and consequently smaller diameter gear that would suit the swing of the dividing head, then cut the coarser and larger gear in the automatic gear cutter.  If one looks in the tables in the Brown & Sharpe Practical Treatise on Milling and Milling Machines, in the table on indexing, that there are a good many numbers of divisions (prime numbers particularly) that must be done by differential indexing. Fewer numbers of division are able to be done on Cincinnati dividing heads due to their use of high number indexing plates.


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## Bill Gruby

Gear cutting is fun once you get the hang of it. I did well here. My rotary table converts to a dividing head with a 90:1 ratio not 40:1 as a dividing head does. That is 316 Stainless being cut.

 "Billy G"


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