worth machining myself; how to begin?

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

At your level, any project will be either crude, or only an exercise. I don't mean that to be condescending in any respect, but you should have reasonable expectations before spending 100+ hours on a vice.
I had to do extensive bench work during my apprenticeship and having a nice bench vice which runs smoothly and works *correctly* was crucial. While it would be reasonably simple to create a vice which resembles a professionally built ball vice, building one that feels and functions correctly is probably beyond your capabilities right now.
I built a small bench vice (fits in your hand) during the first year of my tool and die apprenticeship. It works well with little backlash, virtually zero sideways slop and smooth action. It took 60 hours and I had some ~1,500 hours experience on the machines when I started, if that gives you an idea. (I can send you a photo if you're interested)
If you do decide to build the vice, I would recommend you build the one you want the first time. While larger work pieces do take more time to machine, this extra time is trivial compared to the time required to machine a slightly smaller piece of the same design.
HTH.
Regards,
Robin
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bernard Arnest wrote:

There are plenty of used ones to be found. Several of them here:
http://goldmachinery.com/machinery/antiques/engineturning.htm

Unless you have experience in mold making for cast iron casting and extensive machining experience to produce the various "rosettes" for the rose barrel, I suggest you forget about making a machine like this yourself.
Take a look at this page for some introductory information about these machines and their workings (http://www.rgmwatches.com/engine.html ) This page includes some videos.
And take a look here for a sampling of patterns http://www.rgmwatches.com/engine99.html
Almost every one of these pattern requires it's own rosette. All rosettes produce more than one pattern and almost infinite variations are possible.
Until you develop an intimate understanding of the construction of these machines and how they work, forget about making your own. So I strongly suggest that you save your money and buy one.
Oh, and before I forget, there are two kinds of engine turning machines, "rotary" and "straight line".
Check out the work of Dale Chase for some exceptional work in wood, jade and metal with an engine turning lathe. http://www.makerofboxes.com /
Abrasha http://www.abrasha.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
...

Here's the two key points in your note.
Congratulations on your interest. This interest can take you as far as you'd like to go. Make it a career, or a life long hobby.
Second, take advantage of this machine shop NOW. You've got a well equipped shop AND someone to mentor you. You may not get an opportunity like this again. Make something, anything, and learn all you can.
As to your vice project, sounds like fun. I'd plan on the first one for practice. You ain't a machinist till you screw up, and you will. Then make one again - it will come out real nice.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

Well said, Karl. That's excellent advice. Don't be too disheartened when you do screw up. Figure out what you did wrong and treat it as a learning experience. Also, many of the instructors in college machine shops are real experts, and they'll be pleased to help anyone who shows a little extra interest.
Chris
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I would suggest you consider going to some thrift stores and seeing if you can buy a bowling ball. They are fairly easy to cut and are useful for things as camera mounts, telescope mounts, and mounts for a vise.
I don't want to discourage you from learrning to machine things, just suggest you consider seeing if there are things that can be modified to speed things along.
Dan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bernard, I have a friend in St.Louis that has two of the Rose machines you have described. He has made some very interesting modifications to them that allow him to actually carve the rosettes in wood. He motrorized the cutting head. Just incredible. He makes his own "program" plates out of plexiglass. If you live near STL I'd be glad to put you in touch with him. BTW, the bowling ball is a great idea. Also, I see large stainless or chrome spheres at the junk yard all the time. They come out of large ball valves. Good luck! -Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Never make anything you can get from a scrapyard. It'll be cheaper, and it'll probably be better.
Ball vices are around. More commonly you can find a ball clamp, and a vice, and introduce them yourself.
If you do want to make a ball vice, then don't try making the ball. Balls come from ball factories - they're a pain to make, there's a trade in them, so go find one. Besides which, the idea of buying steel for over $/lb makes me faint. If you ever do need something big and hefty (an armourer's anvil stake for instance) then this is why the good Ford gave us scrapyards, and he gave the scrapyards heavy crankshafts and gave us angle grinders. It's a sin to buy new steel just to machine away most of it.

That's insanely ambitious. So before you do it, you really do need to make a few simple projects first, like the odd Difference Engine or two. I don't want to discourage you, but it really will be quicker and easier if you begin by making some moderately complex things first - you'll simply be _quicker_ with a bit of practice.
There's also the issue that all you've seen first is lathe turning. So at the moment, every problem looks like a turning problem. This is a very inefficient way to work - why turn a ball from bar when you could cast it instead? Why machine from solid for something you can fabricate by welding? The more techniques you learn, the more avenues you have for how to make something.
As far as making the complex cammy parts of a rose engine, then I'd look very hard at CNC, quite possibly CNC milling on a rotary table. You dont have to make a "CNC rose engine" (although the idea is tempting), but certainly CNC is a good way to make some of the complex parts.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.