Metric vs. Standard

[Dan Schultz]

.....Should they not have been metric? What about the threads on the ball pinions themselves? Are they standard as well?

Schlep,

You need to get yourself a set of metric and US thread gages. It's hard telling what some of this stuff is. In some cases, you will even find oddball metric sizes. Wait 'til you get into the threads of piston casings!

[Rick Denney]

Should they not have been metric? What about the threads on the ball pinions themselves? Are they standard as well?

There are several possibilities here.

One is that the ball-and-socket linkages were actually added over here. This was certainly true of my Sanders-labeled Cerveny from the early 80's, where the linkage conversion had been done by the importer.

Another possibility is that Cerveny still has a bunch of SAE-threading equipment, and therefore still thread things using what is now U.S. customary units. After WWII (and sometimes long after the war), European countries migrated to metric dimension systems. But the machine tools they had predated these conversions, and indeed many countries could only get their machine tools second-hand, or from U.S. and British sources. Thus, there are many examples of metric countries using threads in English units. One that I can think of is used in bicycles. Italian-threaded bottom bracket bearings use a metric diameter (36mm) and British threads (24 threads/inch). This is a leftover from the early 50's. Another example is that bicycle chains still have a half-inch pitch, even though nearly nobody in the U.S. makes them any more.

Given that many ex-Second World countries have not updated much of their equipment or design since the immediate post-war period, it is possible that Cerveny is still standardized on threading in inches.

Those are two possibilities, but I'll bet the real reason is that the supplier of the parts primarily makes stuff for the U.S. hobby market. Those ball joints I took off that Cerveny were made by Du-Bro (though it wasn't their more robust stuff that I used to replace it). That's why I suspect that the importer installed it, but it could be that the factory buys parts from the same source, and I'll bet that's the case now.

Rick "who has found that ex-German eastern-bloc photo equipment is largely metric, but ex-American/British European bicycle stuff is still a mix" Denney

[Rick Denney]

Thanks Rick!
Do you think that I might be able to avoid redrilling and retapping holes should I decide to replace the ball pinions with the RC parts later on?

Possibly. All the threads on the parts that I use are 4-40, meaning they use a #4 wire with 40 threads/inch. This is a standard size, and taps are readily available for it. I don't recall the size of the wrench I used for the nuts, but 7/32 sounds about right.

Rick "noting that his old Cerveny's importer used smaller 2-56 threaded parts" Denney

[olaness]

I don't know much about tooling and its history, however I have come across enough measuring equipment to know that metric is metric, but imperial is not always the same. A metre is always a metre and a litre is always a litre, but in imperial measurements there are differences between the american and the english measurements. As far as I'm aware an american mile is slaightly shorter than an english mile, same applies to a yard, and a US pint is substantially less than a UK pint. To me it looks like any US measurements are a bit smaller than the UK equivalent, but I don't know for all the different meaurements. However, anything that komes in imperial rarely states whether it is the US or the UK version being used.

Whether that's relevant to your problem I don't know, but it can be useful to know.

Ola

[Chuck(G)]

Aw heck, Wayne. Be a man and re-tap those holes for some good old Whitworth threads:

http://www.britishtool.com/bswdata.htm

That'll really keep some poor tech 20 years from now guessing...

[Joe Baker]

... in imperial measurements there are differences between the american and the english measurements....

Only in volume measurements (bushels, pecks, gallons, pints, ounces). British and American inches, feet, yards & miles are the same.
_________________________
Joe Baker, who has his own xenophobic quirks but wonders why the heck we don't just adopt the @#&%@ metric system.