Metric Transposing gears for 1334 Standard Modern lathe

Hi all. I am the proud new owner of a Standard modern 1334 lathe. . The lathe came with a bunch of tooling but it does not have metric transposing gears, and I do enough metric threading that that is important to me. I am hoping that one of the other Standard Modern owners here could come to my rescue and help me out. I am looking for some measurements to help me try and source the gears from a source other than Racer Machinery (who want over $1000 USD for the Metric transposing set). Thanks.

Peter

fairmountvewe said:

... Racer Machinery (who want over $1000 USD for the Metric transposing set)

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What is included for that $1000.00?

I do not have a lathe of that model, but generally metric transposing gears consist of a compound gear (two gears that are locked together) with 127 and 100 teeth or 127 and 120 teeth although some have 127 and 50 teeth. They need to be the same face width, pressure angle, and DP as the other gears that go between the spindle and the shaft to the QC gear box. Your QC gear box may have diagrams that show the recommended gears for your lathe if it shows the positions for metric threads.

Any gear shop should be able to make the gears you need. And for far less than $1000.

The 127/100 tooth gear produces an exact English/metric conversion: the resulting metric threads will be as accurate as your English ones which are usually as accurate as your lead screw. But many people save even more money by using a pair of gears that produce a ratio that is only approximate. The 47/37 tooth combination is off by only 0.016% and is probably the most popular approximate conversion. It is just fine for almost all threading that involves fastening parts together (short threads). But it would not be good for making a metric lead screw where accuracy over a longer distance is needed.

I wouldn't hold my breath trying to find a shop that will make the gears for "far less than $1000.00". Yeah, it seems like a lot of dough, but for custom gears, I'd say you have to make your own if you want them for cheap (ie., you have more time than money available). 127 tooth may require some fiddling around making a special indexing plate, too, if cutting these on a conventional mill.

EPAIII said:

I do not have a lathe of that model, but generally metric transposing gears consist of a compound gear (two gears that are locked together) with 127 and 100 teeth or 127 and 120 teeth although some have 127 and 50 teeth.

snipped something)
The 127/100 tooth gear produces an exact English/metric conversion: the resulting metric threads will be as accurate as your English ones which are usually as accurate as your lead screw. But many people save even more money by using a pair of gears that produce a ratio that is only approximate. The 47/37 tooth combination is off by only 0.016% and is probably the most popular approximate conversion. It is just fine for almost all threading that involves fastening parts together (short threads). But it would not be good for making a metric lead screw where accuracy over a longer distance is needed.

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The 47/37 ratio is 1.27027 Which is close...

If you have a 21 tooth gear, you can use an even better ratio of 80/63

The 47/37 ratio is 1.27027 -1.27 = 0.0002707
The 80/63 ratio is 1.26984 -1.27 = -.00015867

That ratio can be built with a 21 tooth gear, and another set of gears with 3:4 ratio

80/63 = (4 * 20 ) / ( 3 * 21 )


So if you already have some change gears, you can build a compound set of gears with them
You might be able to get an off the shelf set of gears to build the compound set, and avoid the custom gears.,


Take a look in McMaster for 20 and 21 tooth gears :

McMaster-Carr

3t3d said:

So if you already have some change gears, you can build a compound set of gears with them
You might be able to get an off the shelf set of gears to build the compound set, and avoid the custom gears.,

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Orrrrrr... there might be somebody that makes Transposing Gears fairly frequently that might be able to help out... Not saying... just sayin....

first thing is to find out what the gear pitch and pressure angle are. then look check out Boston or Martin for the gears you need they may have the gears in stock ken

I made some gear sets for threading years ago. I used 40 and 63 (could have used 80 and 63) for the metric conversion, which yield a ratio of 1.2698 versus the perfect figure of 1.27. As was noted below, 48 and 37 is not quite as accurate.

Larry

You may have to look around a bit. I did and I found a gear shop that had reasonable prices. Delivery was slow.

I can do it fast. I can do it well. I can do it cheap. Pick any two. You need to find a gear shop that already does the DP and PA that you need. They already have the cutters and can do it when the machines are set up for other orders.

Yes, making your own would be less expensive if you discount the cost of your labor. I've looked into that too. McDonald's pays better.

HuFlungDung said:

I wouldn't hold my breath trying to find a shop that will make the gears for "far less than $1000.00". Yeah, it seems like a lot of dough, but for custom gears, I'd say you have to make your own if you want them for cheap (ie., you have more time than money available). 127 tooth may require some fiddling around making a special indexing plate, too, if cutting these on a conventional mill.

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I am not familiar with this particular lathe, but I have made lots of gears for others including metric conversion sets.
I agree with the advice to get commercial gears if possible but the problem is often with the centre holes, are they splined or keyed,this can be a bigger problem than the teeth.
I think that for normal use, the pressure angle is not too critical as you control the meshing onsetup.
If I can help further, PM me
Peter

Wow;

Thanks for all the reply and advice. I have a couple of days off now to start chasing down some of the information and ideas. I do know that the Standard Modern manual shows a picture of a 127 tooth gear and uses a different size idler gear for different size pitches. I will try and find that page in the manual, scan it and post it so you can see what I mean. Again my thanks to all who have helped so far, and to those Canadians in the crowd...Happy Victoria Day weekend...
Peter

fairmountvewe said:

Wow;

Thanks for all the reply and advice. I have a couple of days off now to start chasing down some of the information and ideas. I do know that the Standard Modern manual shows a picture of a 127 tooth gear and uses a different size idler gear for different size pitches. I will try and find that page in the manual, scan it and post it so you can see what I mean. Again my thanks to all who have helped so far, and to those Canadians in the crowd...Happy Victoria Day weekend...
Peter

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It's an old thread I know but I'm curious if you're still needing the specs on the gears? I made a set for mine which I believe are the same as yours (slightly different model) and I could provide the details if you'd like.

I never understood what the big deal is cutting a 127 tooth gear. It's like a lot of other things in this business- many of us have niche capabilities that might appear difficult to others.

Dan from Oakland said:

I never understood what the big deal is cutting a 127 tooth gear. It's like a lot of other things in this business- many of us have niche capabilities that might appear difficult to others.

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I think it comes down to people not wanting to spend money on the things required to do so one time, combined with a general resistance to accepting that gears take time ( & money ) to make properly. You ( I, and others ) get it because you see it firsthand and deal with it frequently. So we understand the impact and accept it casually. But Johnny HomeShop more often than not has to justify it to their spouse or take the hit to their beer fund. So to them it seems so large an imposition.

I never looked back. Once I decided we needed to do it, we did it. And now I'm making 127T gears ( and 127T/100T compounds ) almost every two weeks it seems. I'm sure that you are in the same boat, or its sister. To us, it's just the cost of doing business.

THE big deal in cutting a 127 tooth gear is that is a PRIME number. The worms in the commonly sold dividing heads or rotary tables are usually based on either a 40::1 or a 90::1 gear ratio and neither of these is the least bit useful for dividing by that prime number. You will need a plate with a 127 hole circle and I am not aware of any manufacturer of dividing heads or RTs that even offers one. So, the gear shop (or you) will need to make one yourself.

Here is a thread that discusses making another gear with an odd, prime number of teeth (71). The same ideas apply. If you go to post #27 in it, I describe a method for making a plate with any number of holes. This method is only limited by the accuracy of the worm in your indexing head or RT. Other methods are also discussed in this thread:

calculating dividing head

Yes there are compound dividing heads and other arrangements that will do 127 divisions, but they are usually more expensive and difficult to set up and use. And the divisions can be only good approximations in some cases.

If you do not need to make long threaded parts, like lead screws, then there are a number of gear ratios that provide very good approximations of the needed 127::100 gear ratio. One popular one is the 47::37 pair. Both of these are prime numbers, but the common sets of hole circles usually contain both of them so the gears can be more easily cut in a number of shops. (The common, OEM provided sets of hole circles usually allow all divisions up to 50 before they start skipping numbers. For instance 51 and 53 are not usually provided.)

Dan from Oakland said:

I never understood what the big deal is cutting a 127 tooth gear. It's like a lot of other things in this business- many of us have niche capabilities that might appear difficult to others.

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Honestly im in the not hard camp, but a bit repedative. been there done that and have the 127 tooth gear to prove it. I did it with a Bridgeport, a invalute gear cutter and a 6" horizontal - vertical rotary table (yeah a fucking Vertex one at that). Non of this dividing plate crap either, just a simple list of 127 angular measurements to the second and a pencil to tick em off.

Sure there was a 127 chances of fucking up, hence every cut got tripple checked. Took me about 3 hours from memory. Did a few other gears too, All 14DP to suit a harrison lathe. I did fuck up on the 90 tooth, but hay it runs great in one direction, the other its direction its kinda a 89 1/2 tooth gear (yeah seriously it is), shit happens and i spose in total cutting every damn gear i could think of ever needing i probably cut over 600 teeth based on vernier readings, one fuck up still puts that at about the highest success rate of anything i have ever achieved in this life so far. Hell farting goes wrong more oftern than that when your lactose intolerant

So if i can do it, you have no excuse not to at least try!

As to errors, sure there not perfect, but if you care to work out how much a sub 30 secound angular error makes on a typical 2-4mm pitch metric thread cut with a imperial lead screw on a 40+ year old lathe you got better mesuring gear than me!

fairmountvewe, sir,

FWIW!

I have seen metric conversion/translation attachments where the 50-127 gears are not compounded and integrated in the normal gear train but are adjacent face to face, mounted on a separate plate or banjo type of arrangement, using gears that are very different in PA and or DP/Mod. than those in the normal gear train. Only the ratio matters!

Picture the input shaft coupled to the spindle through a rigid coupling and the output shaft turned and keyed to fit gears normal to the lathe.

From the photos that you have posted I do not see a reverse to lead screw feature on your lathe. You are going to have to address some way to reverse your lathe to actually use any metric conversion/translation.

Good luck to you sir, and hope you have as much pleasure with your new lathe as I have had with my 1333 US govt. reject.


Bob....not the cat.

Greetings all;

First off, I would like to thank you all for participating in the discussion. As some have alluded to, my lathe is indeed in a home shop. This is not a production environment, but rather one where farm and hobby bits and bobs are made. I have virtually no formal training save a couple of semesters of shop class some 40 odd years ago, and a very patient(and talented) son who is a machinist with our Armed Forces.... oh and You-Tube.....

I bought the Standard Modern as an upgrade for a SB9A I have worked on, refurbed, added to and generally really enjoyed because it really wasn't too intimidating. I naively thought the SM 1334 would be a more capable machine. Capable of what, I am not really sure yet, but capable just the same.

One of the things I bought for my SB9A was a set of metric change gears. My son patiently showed me how they were installed, how the process worked, some general pitfalls to watch for and off I went. I even managed to repair some parts on our Disc-bine that saved us a ton of money over buying parts at the dealership.

The SM 1334 did not come with change gears. I don't know how to measure things like DP or PA, in fact I barely even know what they are. I can measure the thickness of the current gears, and I can count teeth. I guess what I am after is a picture of how the change gears are supposed to be mounted (something my manual does not show and something very different from the SB9A), and exactly what gears I should have to produce a moderate array of metric threads. Much of the theoretical discussion above is way beyond my current ability to comprehend. I need it dumb'd down a notch....

Again my thanks to all who have taken the time to contribute to this discussion. I really do appreciate it, and I really do learn a lot from them. You are to be commended.

e: How to ID the PA (pressure angle) and pitch.

First the pitch. English system (inch based) gears are generally specified with the DP. Assuming that you have a sample gear, count the teeth and add two. So if your gear has 20 teeth, 20 + 2 = 22 teeth. Then measure the OD. It is better, more accurate if you have a gear with an even number of teeth for this and also the more teeth, the more accurate your result will be. Now, the DP or Diametral Pitch is the number of teeth per inch of the pitch diameter. This applies to the actual number of teeth and the pitch diameter which is at the middle of the tooth. BUT, standard gears will also have this relationship be true at the OD of the gear if you use the actual number of teeth plus two. That's why I said to add two to the tooth count.

So, divide the tooth count plus two by the OD and you should have the DP. Now if that comes out as a whole number or close to it, then the gear is inch based and you have the pitch.

But if it does not come out even, then you may have a metric gear. Metric gears are specified in Module and that is defined differently than DP. Module is defined as the pitch circle diameter in mm divided by the number of teeth. It is a unit of length and a module 1 gear will have a distance of Pi times 1 mm or 3.141 mm from tooth to tooth along the pitch circle. Mathematically:

M = PitchDiameter in mm / number of teeth.

And the conversion from the English DP to the metric M is as follows:

M = 25.4 / DP

So you can convert the DP number you got above to metric module. One of these two figures should come out close to a whole number and that will tell you what kind of gear you have, English or metric and it's pitch.

Now, the PA or pressure angle. There are two common pressure angles in use, 14.5 and 20 degrees. The best way to determine the pressure angle is to try the mesh of the unknown gear with a known one. But that requires having a known gear of the same pitch and most people do not have an assortment of such known gears.

The visual appearance of these two pressure angles is sufficiently different so that you can tell which one it is by comparing the tooth shape of an unknown gear with the image of known ones with similar tooth counts. Many sources have such images for gears of an intermediate number of teeth and these can be used for a visual comparison.

Greetings all;

First off, I would like to thank you all for participating in the discussion. As some have alluded to, my lathe is indeed in a home shop. This is not a production environment, but rather one where farm and hobby bits and bobs are made. I have virtually no formal training save a couple of semesters of shop class some 40 odd years ago, and a very patient(and talented) son who is a machinist with our Armed Forces.... oh and You-Tube.....

I bought the Standard Modern as an upgrade for a SB9A I have worked on, refurbed, added to and generally really enjoyed because it really wasn't too intimidating. I naively thought the SM 1334 would be a more capable machine. Capable of what, I am not really sure yet, but capable just the same.

One of the things I bought for my SB9A was a set of metric change gears. My son patiently showed me how they were installed, how the process worked, some general pitfalls to watch for and off I went. I even managed to repair some parts on our Disc-bine that saved us a ton of money over buying parts at the dealership.

The SM 1334 did not come with change gears. I don't know how to measure things like DP or PA, in fact I barely even know what they are. I can measure the thickness of the current gears, and I can count teeth. I guess what I am after is a picture of how the change gears are supposed to be mounted (something my manual does not show and something very different from the SB9A), and exactly what gears I should have to produce a moderate array of metric threads. Much of the theoretical discussion above is way beyond my current ability to comprehend. I need it dumb'd down a notch....

Again my thanks to all who have taken the time to contribute to this discussion. I really do appreciate it, and I really do learn a lot from them. You are to be commended.

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Well hello and sorry to revive an old thread like this but....I went to order a few things for my 1334 and was shocked. a steady rest and metric gear train was just over $5k USD. so if any of yas are making the metric gear train for sale or happen to have a spare steady you would like to sell please let me know. im interested.

Thank you

LG