Hi, I'm interested first in machining a ball vise for engraving, and more ambitiously, making my own rose engine.
I'm a freshman in college now, and we have a machine shop. I took an intro class, in which we made a crude flashlight out of aluminum. Mine wasn't perfect, but it covered all the basic skills. My point being that I'm not that experienced yet at machining, although I do at least have basic experience, and additionally the shop managers can help me with what I don't know how to do.
The ball vise is just that: a hemisphere on bottom sits in a plastic ring. The hemisphere at top has two jaws forming a vise. A left and right-hand-threaded screw opens and closes the jaws, which ride in a t-slot. Ball bearings inside let the two hemispheres rotate where they meet. They are built from 4" diameter, useful only for small jewelry, to 6.5" (the size I have drawn plans for, although I feel I could adapt them to other dimensions), to as much as 8-3/4" diameter, for rifles, swords, or for example, someone who used such a large vise to engrave all the parts on a watchmaker's lathe.
For what I want to do, I will need a larger vise. 4" diameter can almost be found as scrap, a length of 6" diameter mild steel rod will cost $66 from the campus machine shop (@ $1.10/lb, I believe), and a length of 8" diameter mild steel will cost $212. The solid mild steel rod stock used to machine the two hemispheres will be the single greatest cost, although of course I realize other parts (bearings, threaded rod, the smaller rod stock for the jaws) could add $20-$60. That's a lot of money to play with; worth every penny for a quality vice, but if I screw up machining a $200 chunk of steel that would suck. What is your advice? Start with the 4" vice, then jump to the
8" vice if that works out? Maybe start with another totally different simpler machining project first, (i.e., sharpening jig, or pointing jig for sculpture, I had in mind)?As another option, a friend recommended possibly using a large hemispherical cap used in plumbing to save cost and machining time (I wouldn't have to machine out the inside nor, more importantly, need to used the cnc lathe to turn a rod into a perfect hemisphere, which is a lot of material to remove. My friend, a dentist, proposed to then precisely cast the cavity in dental stone and press the bearings into that, and mount an old lathe chuck on top (which he already has) as the vise on top. Is this worth a shot? It would certainly be easier and cheaper. On the other hand, a lathe chuck is not the same as a parallel jaw vise, I don't trust that the dental stone won't crack under the stresses of chasing, and finally that the fact that this easier design is not the standard might mean something.
Regarding the rose engine: I want to build the engraver's ball vise over January, it is something that I am doing now, so the question of the rose engine is less important to me. The rose engine is for the more distant future, summer at soonest but probably years away; depending on just what the logistics are?
So anyway, it is a machine used for fine mechanical engraving, fairly simple in principle. A shaft both turns in bronze bearings and can move linearally back and forth in them. Along the shaft is mounted a series of "rosesettes," bronze plates with contoured perimeters. At the far right is a chuck to hold the work, and to the right of that a moderately complex vise holding the graver. A "rubber" rides on the rosettes, held against them with powerful springs, and is linked by a shaft to the vise/graver. In this manner, as the shaft turns, the contour of the given rosette the rubber is riding on pushes it back and forth in a pattern, and as the work turns (being on the same shaft with the rosettes), the rocking motion of the graver dictated by the rosette engraves a pattern.
This should give a general description of it. I have some cruder drawings, an understand of how it works, some photos. I could possibly design my own. Also, it's possible that the Society of Ornamental Turners may have plans, and a machinery dealer 2 hrs away does have some antiques (well, all existing rose engines are antiques now) to study as well, so if I go ahead with it I think I can find or develop solid plans.
If I buy one, it will be a minimum of $2000 for a fixer-upper. There is a short supply, they were last made in the early 20th century and not in the same volumes as more general bandsaws or metal lathes; they're a specialty machine. Thus in looking for the past few months, there are a couple on the market that aren't fixer-uppers but are closer to $4000. They weight around $600 lbs, needed, despite the tiny scale of the work being done, to prevent someone walking too heavily along the floor upstairs giving you tiny blips in your work. The more weight, the more absorpsive of vibrations and the cleaner the work. The design isn't the most complex, less so than a typical metal lathe, although still quite complex, certainly much, much more so than the ball vise. And that's also a lot of weight, which should give some indication of just how much machining would be involved. A good portion of that will be in the cast iron stands included in these machines.
Maybe from this information, you could very roughly estimate for me just what sort of project I would be getting myself into? For even $4000, is the amount of machining this might involve just too much? I could probably afford the steel, but could not afford the $4000, not yet, although maybe 5 years down the road when I'm out of college and have a real job. If it's going to take 800 hrs of machining, I would rather wait the 5 years, but if it might be feasible to build, in a reasonable amount of time...?
thanks for your advice! -Bernard Arnest