Going through an old box and haven't a clue

[Bi11Hudson]

Fill who in how?

.

 

[Janderso]

Just a comment; if the 100/127 pair will mesh with what you have, I would say to hang onto them. They'll come in handy some day soon.

I'm not aware of the significance of this gear patter/ratio. Please advise.
Just trying to learn something new.
Thank you sir.

 

[Bi11Hudson]

Metric conversion to Imperial(English) or vice-versa.

When a lathe(for example) has an Imperial lead screw and metric threads are desired, there must be a conversion. 127 is the lowest number(prime number) that is divisible by the conversion ratio. 25.4 mm=1.00 inch. This is accurate to about 6 decimal places, 25.4 times 5 equals 127. There is an error, but so small that the conversion can be used to get to the moon.

Up front, 100 is divisible by 5. There is also the use of 120 (common on lathes of Chinese ancestry), because it is divisible by 3 as well as 5. The bottom line here is the first step for metric from imperial conversion is 127/100 or 127/120. This also works the other way, a metric lead screw to cut imperial threads. There are several uses for this ratio but a lathe lead screw is the most common and frequently used, especially in the hobby arena.

There are ratios that come very close with smaller numbers.(smaller gears) They are not exact, but close enough for most applications involving short threaded portions. A nut will work, a bolt usually will, a long screw like a lead screw will have a measurable error after a very few pitches.

With 127 being a prime number of higher than the capability of the average indexing head, such a gear is not widely available. A capable dividing head is available that can do such a prime number but is far beyond the means of even a middlin' sized job shop. I have a set of fraction plates from U S Steel's machine shop, the best equiped shop in the region in its' time. But they only go from 51 to 97, not the 127 needed. With the "loss" of industrial capacity and knowledge from the united states, this has become even more so.
Political: The use of lower case in the country's name is intentional. End political.

As it happens, I have a Chinese lathe with metric to imperial(english) conversion. the change gears are Modulus 1, 25.4 DP. My Atlas/Craftsman lathe has 16 DP gearing. By using the Mod.1 gear from the Chinese machine as a pattern, I have produced a 16 DP gear with 127 teeth. In plastic, a mis-statement from another post. I would like Iron, Zamak(Atlas), brass or at least Aluminium. Lacking a piece of Aluminium of sufficient size, I made one out of a scrap of plastic. Not strong, just junk plastic. But it works for the small threads I'm interested in. 1mm pitch, about 25.4 TPI being very large to me, For a while, anyway. It won't last long but I don't do much threading these days.

When I, and several others, expressed an interest in the 127 tooth gear, it is for that reason. I don't expect to actually have access to that particular gear, but I would like to. I have (Russian?) both 16 DP and Mod. 1 gear cutters, complete sets. But cutting 127 teeth is a long (time) process. And one slip means starting from scratch, with new material. I probably could find a brass gear from Boston Gear, but that would be very dear. Since I have a plastic gear, such is not a high priority, just sitting in the back of my mind until chance provides the opportunity.

I don't know if I answered all your question, but this should be enough to at least ask the right questions. There is a very broad knowledge base available on this site. I'm sure that, over time, you can find out just about anything you want to know about machining.

Bill Hudson​

 

[RandyWilson]

Meh, my old South Bend takes 120/127. This has more to do with the 6TPI lead screw rather than the more common 8 or even 4. Since I really have a need to cut metric, mostly 1.25 and 1.50, and I'm tired of fighting the mini-lathe to "get close", I sat down and made myself a 127 plate for my dividing head last weekend. Finished it off hours before this 127 showed up mere miles from me.

 

[silverforgestudio]

Apologies for being off line for a couple- Work has to happen- And I certainly appreciate the education you guys have helped me with- Thank you folks.

The Double Keyway gears look like Atlas/Craftsman gears.
Many of those were used with the Double Keyway and paired up together.

Thanks Yendor- I appreciate it! Im getting an education in just listening to the folks chat here- and I honestly think this is why I like this forum- Im new to tooling, still learning and trying to "build" a shop as I go... and everyone usually has a tidbit or a thought that builds on my knowledge- So Thanks!

The 7 1/8" diameter , 127-tooth indicate it is an 18-pitch gear, and could be suitable for a South Bend 9/10k lathe. The same applies for the 100 tooth. There are definitely going to be other applications, but the only real intended application for a 127 tooth gear is full conversion for metric thread pitches. For example, you could use that gear as an index to machine something else with 127 holes (or similar).
The previous batch, the 34 tooth is a 14 pitch, and the 45 tooth is a 16 pitch. It looks like a very eclectic assortment of gears. 14 pitch for the small ones, 16 pitch for most, and an 18 pitch metric conversion.

I will certainly agree on eclectic- I have "found" more gears in another set of boxes from the sale. Im just gonna have to put them up and get them back out when I have more knowledge.
On a positive note- It has convinced the wife to let me get a set of Pitch Gauges and a few "tools" for measuring... So that is a definite step in the right direction!

I sat down and made myself a 127 plate for my dividing head last weekend. Finished it off hours before this 127 showed up mere miles from me.

Sounds like my luck as well... Bad timing on my part!

The pitch gauges and the calipers will be here (hopefully) by Friday- So with that, the formula for DP and a few other tidbits from you gents will allow me to catalog the gears better!

Thanks again folks!

 

[SLK001]

Here is a hub shot of the 100T gear with empty pin hole in hub

That empty "pin hole" in the hub is the lubrication point for the gear. The DP for your transposing pair is 18, so it is for one of the smaller lathes (like a SB 9" or 10K). THAT gear pair is easily worth $200-250 by itself. Add some of the other spur gears that mesh with the 18 DP set and you're talking real money for the set!

 

[silverforgestudio]

That empty "pin hole" in the hub is the lubrication point for the gear. The DP for your transposing pair is 18, so it is for one of the smaller lathes (like a SB 9" or 10K). THAT gear pair is easily worth $200-250 by itself. Add some of the other spur gears that mesh with the 18 DP set and you're talking real money for the set!

Thanks SLK- I was thinking the pin hole was to "mount" another gear to the set- thanks for clarifying!

I will be going through the rest of the box and documenting the DP/PA and tooth# on each- Lots of sharpie marking coming up!