Rivett 608 Precision Back Geared Screw Cutting Lathe
Rivett Lathe and Grinder, Inc. - Brighton, Massachusetts
The lathe on display in this exhibit was manufactured in 1944 by Rivett Lathe and Grinder, Inc. of Brighton, Massachusetts The 608lathe could be found in laboratory shops in places like Harvard, Johns Hopkins and Yerkes Observatory. They were also present in leading edge industrial laboratory shops and several were sold into the Edison shops in West Orange, NJ. The 608 lathe at CRMII was the first lathe at the Polaroid corporation, and was donated by Mrs. Wolff in memory of her husband Otto E. Wolff, Vice President, Engineering, Polaroid Corporation.
It is interesting to note that Edwin Land (Founder and President of Polaroid) was asked by his 3-year-old daughter sometime in 1944 why she could not see the picture he had just taken of her. Her request led to the development of the Polaroid Land Camera in 1948. So it is altogether possible that the specific lathe you see here actually played a role in the development and early manufacture of that ground breaking camera product.
The 608 lathe was the result of adding screwcutting capability to Rivett's 8" plain bench lathe, introduced in the late 1890's. It was also one of the last lathes designed by Edward Rivett. The 608had the second largest production of any of the larger Rivett lathes, about 1800 total. The basic lathe changed little from its introduction in 1920 until production ceased in 1960. Approximately 1800 units were produced. Part of the reason for the large production of the 608 was its popularity with the military during World War 2 where it was used on shipboard, in maintenance depots and shipped in large quantities to Great Britain. The 608 is considered by many familiar with them to be one of the finest small lathes ever made.
The lathe on exhibit was delivered in one of several available bench mount configurations, incorporating the lathe with a work bench, drive motor, and overhead countershaft, as shown in the catalog image below. However, the Polaroid purchase varied from the catalog configuration in one respect, it has what appears to be a customized motor drive and motor mount, as also shown below:
Origins and Features of the Rivett 608 Precision Bench Lathe
The 608 lathe had it's origins in the "8" Precision Lathe" of the late 1800s. Like it's progenitor, the 608 is an ingeniously designed machine, exceptionally well made and beautifully finished - but, so expensive that most of them found their way into the hands of the military, Government or industrial research and development laboratories.
Equally famous in both the USA and the UK (many examples having been sent to Britain during WW2) a 608 in "civilian dress" would normally have glistened all-over in an imposing, fully machined, then hand scraped and polished finish, as shown in the photograph below of the cross-slide and compound-slide assemblies.
While most lathes use only the top face, and upper edges of their beds to guide the saddle (carrying the cross and compound slides), on the Rivett the front face of the bed, formed into dovetails and plain ways, was used to support the apron as well. This resulted in a very stiff structure beneath the cutting tool and a saddle-to-bed bearing area of 74 square inches. The upper and lower dove tails can be seen in the picture below of the front face of the 608.
The picture below also shows the novel arrangement of the 608leadscrew; it was sunk into the front face of the bed with a good proportion of its rear section fitting very closely against the semi-circular channel in which it ran; this resulted in a well supported, flex-free shaft.
Finally, the picture below further shows that all 608 models were fitted with both a leadscrew and a power-shaft, so preserving the accuracy of the former when simple power sliding and surfacing feeds were required. The drive to the power-shaft was arranged, very simply, by a gear keyed to and sliding on the leadscrew which engaged a fixed gear beneath it on the power shaft; the two gears were covered by a rather elegant nickel-plated bronze cover which slid in groves on the face of the bed. An automatic-disengage mechanism was fitted to the carriage drive and this, with Rivett thoroughness, was fitted with a small micrometer dial and could be set to stop the cut to within 0.001".
And one further note, the picture above shows the actual CRMII 608 lathe prior to being cleaned up. As you can see by looking at the lathe on it's bench, under all the grime and dried oil, the fine surface quality of the lathe has survived 75 years hard duty in the Polaroid machine shop.
Typical of the well thought-out features included in the design of the Rivett 608 was the fact that no tools, apart from a chuck key, were required to operate it. A slender lever (it can be seen on the end of the cross-slide base) released the compound slide rest and it could then be instantly re-positioned, or slipped off to be replaced by a variety of beautifully-made accessories, including a vertical milling slide, hand-tool rest, saw table or indexing, slotting, ball-turning and relieving attachments.
Due to their robust design and construction, many Rivett 608 lathes are in continued use today, nearly a century after the product line introduction. They continue to serve hobbyists and laboratories well, as the lathe on exhibit served Polaroid well for nearly 75 years.
For Further Information
If you would like to learn more about the fundamentals of lathes and the different kinds of lathes, please try out some of the links bellow:
What is a lathe?
What are the parts of a lathe?
What kinds of lathes are there?
What are the origins of the lathe?
What is a Bow Lathe?
What is a Spring Pole Lathe?