New guy with questions. Craftman 6" lathe

[Harold_V]

im not sure how you go about getting the tool geometry right if that makes sense.

Yes, it does make sense, because the typical rocker tool post was used in conjunction with tool holders, which provided a given rake angle. As you move the rocker to achieve tool height, the back rake angle will change, as will relief angles of the tool in use. You have to take that in to account when you grind tools---so they're not really interchangeable with other systems. You've very well served to ditch the rocker post.

I purchased my Sag 12 Graziano lathe 50 years ago (1967). It was shipped with a rocker tool post, which has never been on the machine in all those years. A rocker tool post, while relatively flexible in that you can pretty much achieve any tool angle required, is absolutely worthless for anyone who works with dials (or a DRO, for that matter). Once you coordinate the cutting tool with the dial, all is lost if you move the tool, so repetitive parts become very difficult to machine. Any kind of quick change, including the old standard square indexing turret, is leaps and bounds better.

You mentioned being a machinist, but never have used a rocker post. I was hired in the tool, die and gauge department at Tooele Army Depot during the Viet Nam war. They were engaged in rebuilding armored troop carrier, amongst many other projects. Imagine the shock I experienced when I showed up the first day, to find rocker tool posts on the lathes. We had to work (mandatory) five 12 hour days and two eight hour days weekly, which went on endlessly. They did everything they could to keep up production except provide equipment that would make one's time better spent. I lasted two months and couldn't take it any longer.

H

[spro]

Okay. I accept all that. Done. Not done because lantern style allowed the unique configurations which home shops used. One off or two, then something different. The only argument I would have, is to throw them away. Properly configured, they/tool holders reach into awkward areas. I have turrets set up with tooling for regular work but there is always the rocker which can slide right in there, with some unique bar to do something else.
Also, I'm not sure that light machines favor the positioning of the cutting tool leading the mounting axis. South Bend 9 offered them as well as heavier built different small lathes but there was always an option other than a turret...or in these days a QC toolpost which further limits that ability.

[spro]

Since I already said "don't throw them away" , I mean, somebody could use them. If you receive a lathe with only a bare lantern and some tool holders for that, you can still make things happen. Just because a lantern fits the compound doesn't mean it was the right one for the tool holders. The tool holders in all sizes, had an included angle at which the cutting tool is held. Correct size for that lathe allows a nominal back rake. That way, you don't take a perfectly good Rex AAA or better and immediately have to grind half the top off. There is a balance into how it fits into the holder and the tool post. Don't think the post and dished ring and rocker are the only ones used. Those rings and spacers meant something and so did the other rocker. The "Other" rocker and ring was to set up other tool holders which held the tool straight, or for boring bars or for a larger or smaller tool holder. So we can see how this relates to minute play in cross slides. The tool holder within the lantern, had to be set so that it beared against the tightened lantern walls for the direction it was used. If a person got a mismatched bunch of things, it takes a while to put this all together but the concepts make sense because they Have to.

[spro]

http://www.youtube.com/watch?=t7g8yu2iYhY

[chiefpeyotecoyote]

loved that video thanks for putting that up

[pete]

There's a guy on Youtube by the name of David Richards and most of his videos start out with the title Old Steam Powered Machine Shop. He's collected, restored and put togeather a historicaly accurate 1920's-1930's type machine shop that's almost all powered off a single cylinder steam engine and line shafts. And he still uses that rocker tool post on his old South Bend. This is also a working commercial machine shop although I don't know how much actual paying work he takes in. I remember real well using a rocker tool post back in high school shop and how frustrating it was mostly because I didn't know enough. While old machine tools are really cool and I own a few, I'd still take even a Chinese built quick change tool set up over those rocker tool posts, VFD's with 3 ph motors, and good accurate dros added to the old machines. Some things are better and a lot easier today than they were back then. I've read a few posts on various forums about people still using the rocker style once in awhile simply because they allow the tool to reach into places a tool turret or quick change can't. It would have to be something pretty strange, but I guess they have there place.

[spro]

To be straightforward about this, Steve M has mentioned these videos many times and HV helped post this one. Chipbreakers, or grinding a chip breaker..... Harold has been telling us about chip breakers for years.
All these different mounting systems co exist into knowledge of what is actually happening or doesn't.