rhb
Aluminum
- Joined
- Apr 27, 2019
- Location
- A small town in central Arkansas
I'm a retired research scientist. But long before I became a scientist I was hopelessly perverted by C.L. Stong's volume of "Amateur Scientist" columns from "Scientific American".
In the late 40's John Strong, a premier experimental physicist, constructed a new ruling engine at Johns Hopkins. IIRC this was the first successful build since the 3 engines Rowland built 50 years earlier. A.A. Michelson failed in his attempt which says a lot about how hard a job it is. Though in fairness to Michelson, he had *very* ambitious goals.
The person selected to machine the pair of screws which positioned the carriage and stylus was David Broadhead, an amateur. After eliminating all spindle errors, Broadhead rescraped his 13" Southbend so that the ways were flat and parallel to less than a tenth over the entire length.
I have a 10x20 Clausing 4902 and a 6x24 8520, both of which are large enough for anything I expect to do. I bought the 8520 in "as new" condition with the original inspection sheet which it still met 30 years later. The 4902 has seen quite a bit more use, but is still in good shape. But it does need TLC.
I want to "recondition" these machines to the limits of my ability to measure the errors. I bought and read Connelly cover to cover 20 years ago, I read "Foundations of Mechanical Accuracy" by Wayne Moore long ago, but only got a personal copy a few weeks ago. Any book I come across that discusses high precision and accuracy machines I buy. Suggestions welcome.
In preparation for rescraping the 4902, I bought a 7x14 Chinese machined casting set to practice on. I intend many alterations to the Chinese casting set design, but in this forum I'd like to use it as a case study for discussing the nuances of scraping the alignment of a lathe to the limits of mensuration. I chose that machine for a warm up exercise because they are cheap and, tuned to high accuracy, a convenient size for making gauges or precision RF connectors which tend to be *rather* pricey.
I "reconditioned" a new Chinese 4" x 6" bandsaw from ENCO to cut square and precisely about 25 years ago by traditional benchwork. It was a lot of work, but well worth it. But I've not done much such work since. So I'm rusty. Hence my desire to practice on something less valuable than my 4902.
I hope by Monday to have a 3 point mount with differential thread leveling screws on which to mount the 7x14 lathe bed. However, the rest will not be quick. To compensate for the deflection of the floor, mount, etc I plan to attach a pair of levels to the bed and then use another pair of levels and a small microcontroller (e.g. Arduino) to compensate for the movement of the bed as I move around it and report the deviation of the surface I'm working from the reference plane. I wander between electronics, metal work and programming as suits my needs and interests. I am well prepared.
At present I'm trying to get pricing on commercial sensors. I can build suitable sensors from Chinese level vials for about $15 each which will provide better than 1 millionth per inch accuracy. For a few bucks more I'd rather buy them.
My hope is that others, even if not interested in pursuing the absolute limits of accuracy will be interested enough to contribute their insights into the problems associated.
Scraping is time consuming, but easy to do. Mensuration is another matter.
Have Fun!
Reg
In the late 40's John Strong, a premier experimental physicist, constructed a new ruling engine at Johns Hopkins. IIRC this was the first successful build since the 3 engines Rowland built 50 years earlier. A.A. Michelson failed in his attempt which says a lot about how hard a job it is. Though in fairness to Michelson, he had *very* ambitious goals.
The person selected to machine the pair of screws which positioned the carriage and stylus was David Broadhead, an amateur. After eliminating all spindle errors, Broadhead rescraped his 13" Southbend so that the ways were flat and parallel to less than a tenth over the entire length.
I have a 10x20 Clausing 4902 and a 6x24 8520, both of which are large enough for anything I expect to do. I bought the 8520 in "as new" condition with the original inspection sheet which it still met 30 years later. The 4902 has seen quite a bit more use, but is still in good shape. But it does need TLC.
I want to "recondition" these machines to the limits of my ability to measure the errors. I bought and read Connelly cover to cover 20 years ago, I read "Foundations of Mechanical Accuracy" by Wayne Moore long ago, but only got a personal copy a few weeks ago. Any book I come across that discusses high precision and accuracy machines I buy. Suggestions welcome.
In preparation for rescraping the 4902, I bought a 7x14 Chinese machined casting set to practice on. I intend many alterations to the Chinese casting set design, but in this forum I'd like to use it as a case study for discussing the nuances of scraping the alignment of a lathe to the limits of mensuration. I chose that machine for a warm up exercise because they are cheap and, tuned to high accuracy, a convenient size for making gauges or precision RF connectors which tend to be *rather* pricey.
I "reconditioned" a new Chinese 4" x 6" bandsaw from ENCO to cut square and precisely about 25 years ago by traditional benchwork. It was a lot of work, but well worth it. But I've not done much such work since. So I'm rusty. Hence my desire to practice on something less valuable than my 4902.
I hope by Monday to have a 3 point mount with differential thread leveling screws on which to mount the 7x14 lathe bed. However, the rest will not be quick. To compensate for the deflection of the floor, mount, etc I plan to attach a pair of levels to the bed and then use another pair of levels and a small microcontroller (e.g. Arduino) to compensate for the movement of the bed as I move around it and report the deviation of the surface I'm working from the reference plane. I wander between electronics, metal work and programming as suits my needs and interests. I am well prepared.
At present I'm trying to get pricing on commercial sensors. I can build suitable sensors from Chinese level vials for about $15 each which will provide better than 1 millionth per inch accuracy. For a few bucks more I'd rather buy them.
My hope is that others, even if not interested in pursuing the absolute limits of accuracy will be interested enough to contribute their insights into the problems associated.
Scraping is time consuming, but easy to do. Mensuration is another matter.
Have Fun!
Reg