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One more issue to consider as well. All watchmaker lathes use 8mm WW collets. These collets are the best choice for small parts but do not hold as well as the ER collets. WW collets also do not have the contraction properties that the ER collets have so ER collets may be a better choice for the larger parts. When the WW machines were designed the ER collets had not been invented yet. This is just something to think about when selecting a particular machine for a particular job. Another thing to think about is what are the watch manufacturing companies using today to make watch parts. I guarantee you that they are not using 19th century lathes and collets to manufacture their parts.