First of all, I would like to thank everybody for the overwhelming response and a thoughtful approach on everyone's part.
As picture is worth a thousand words, here is some of the stuff I do:
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I am sure that these will sway the answers to the lathe side on account of most things being round, however consider that I use * what is available* and *what is cheap*. So mild steel most often, occasionally brass. Many a time something grabs me in a garage sale and is put away for later use when I suddenly find its place in a project.
I am located about half-way up the Vancouver Island. I have had people make things for me in the past: The largest dial wheel (Thames) was machined for me in a Quesnel machine shop. It cost me $30 in 1994 dollars. The final piece is still around admired by many who are unwilling to part with the $195. At one stage I was toying with the idea of having the face designs etched by laser, however the cost of this process would have rendered the smaller pieces uneconomical.
Thus in general I would prefer to do as much of my own work as possible. Also it is an excuse to spend large sums on tools. At this point I am still at a stage of collecting information and, as somebody said, there are still a few avenues open for me to get my hands on a lathe or a mill for a trial.
There is no rush. Until then I shall stick with the 18th century methods :-)
You are going to want a standard size mill with a rotary table plus a lathe with suitable swing for your largest pieces. I suspect that you are not holding close tolerances so really expensive equipment is not necessary.
But a CNC c>> you would do much better to describe the work, materials involved, quality
Thank you. You are absolutely right - this equipment is essential! I shall tell my wife... Seriously though, you are right about the tolerances. The times I get frustrated is when I run into problems with symmetry rather than size not being quite right. Also matching angles - to get the gnomon to come out where it should there have to be sometimes 4 different angles just right. The smaller the piece the more critical it is. I have overcome many of these problems by designing things so that there is room for final adjustment but that goes only so far.
Still, if it was easy what would be the point of doing it?
Other than being round and artsy the parts aren't much different from electronic control panels; large and thin with free-hand shapes cut in them. They could be done on a low end mill-drill like the RF-31 and a rotary table with plywood top covers.
You could make the gnomon on a very small lathe, turn the end of it in the mill, or get a rotary table that stands upright and put a chuck on it. You can cut a large variety of angled flats and curves with 5C collet blocks, which will hold a long one-piece rod.
If you turn it on the mill don't let the stock extend more than 3 - 5 diameters from the collet and take light cuts. Otherwise the rod is likely to catch on the tool, bend, and then crash into the tool on the next revolution. It can bend the same way in a collet block but at least it isn't spinning. A lathe (or rotary table tailstock) supports both ends so you can cut anywhere along the rod.
Old-time mechanics cut metal with hand held chisels on wood lathes. My small lathe is set up for similar work with a 1/2" drill chuck on the spindle and a Dremel drill on the tool post. I kept it after buying the larger South Bend because it spins much faster and disassembles easily to clean off grinding grit. A lathe is fairly easy to cobble up from a drill or motor if you don't need the precision bed.
Free-hand milling is easier on a mill with a fairly short table so you can reach the cranks comfortably. That's one of the few things I don't like about a Bridgeport. The RF-31 I bought for electronics had enough table travel to drill both ends of a 19" rack panel but it was short enough that I could stand at either end of the table and turn the handle while watching the end mill approach a scribed line.
I don't think a medium-sized lathe would help you much for these projects. Possibly a combo would work if you get a really good deal on a used one that doesn't have stripped gears. You could build up a wooden support table under the end mill and use the carriage feed to move the disk for engraving. The Smithy I used was an acceptable lathe but it was crudely finished and needed cleanup. If I owned it I could have made something useful out of it eventually. That shop had a CNC lathe and Bridgeport and I only used the Smithy when they were busy.
I have an original, unused milling attachment for my South Bend. The first time I tried it I found out why it was unused. The carriage is meant to take downward thrust only and it jumps around from sideways milling forces. The clamps under the rear are only good enough for knurling.
Looking at your work I would recommend a post-type milling machine with a very wide (Y direction) table, along with the largest rotary table you can handle/afford/fit. 12" diameter would not be too big. Fit motor drive to the rotary table if you can. Use a piece of MDF for custom work holding fixtures.
With a little attention to fixturing, the production of those dials would be a breeze.
Perhaps you should also consider a metal-cutting bandsaw to cut blanks from larger plate/sheet, although a recip. saw with appropriate blade would suffice.
Because accuracy is not a primary concern, Ebay and other advertisers are your friends.
For all that engraving it would be worthwhile to fit CNC control.
Am I mising something? If the shill bid wins the seller still has to pay EBay the final value fee, right? That has got to get expensive in the long run or if done with any frequency.
Presumably the shill account will not be paying by PayPal :-) However, soon nobody will be allowed to use cheques or money orders anyway.
my observation is that reliable tools gets top $ on their ebay auction - however, to their credit, if there is something wrong they make it right - I haven't bought a $$$ thing from them, but I did get a small tool holder, which they sent to me - it was damaged, I picked it up locally (when they still had a retail store) and they credited me immediately, no questions and I got some other stuff.
There is a lot of information to digest. I have been all over Google to find out e.g. what the heck is a rotary table etc. :-). I am trying to relate it all to what I do and it always comes down to the same thing: I gotta see it! I believe there are some good videos out there I shall try to look at.
Today, for instance, I cut off a lip off a small (9cm diameter) circular brass ashtray with a coping saw. That was easy. To restore a circular profile cleanly was done with some difficulty by rotating the ashtray with the edge along the disk sander. The clean up of the surface was even more tricky as the concave shape did not allow the use of my favorite pam sander: It was all done by hand and patience. Scotchbrite pads really helped. The result is not too bad and it is ready to receive a face of some sort.
In relation to this thread I was wondering how the machinery would have helped. Would I be able to mill the circumference with greater precision on a rotary table? What about the surface - is milling the answer? I have been trying to find a way to spin these pieces at relatively low speeds and apply the abrasives to them in a more controlled fashion. I cannot get past the issue of clamping them securely but I suspect you will tell me that there are chuck configurations that will do all that.
I was interested in your comments about cobbling up a sort-a-lathe from a drill press. I have been wondering about that for some time (and now even have a drill press to spare). I even have a live centre of sorts for the use with sanding drums. Maybe I should have a look at this again. The only problem - the said drill press does not go lower that 720 rpm. But for small parts it sould not be a problem.
Your advice coincides with a few others and shall be looking in that direction in a more focussed fashion.
When you say "rotary table with motor drive" is this to allow repositioning of the table to allow, e.g. milling slots, or is it a drive to spin the table sufficiently fast to allow some lathe type operations (right now I would find it helpful to be able to spin some fo the pieces around 50 rpm and apply abrasives, particularly if the pieces are not completey flat)?
A month ago I walked away from a 7x10 band saw with a hydraulic feed in a garage sale. For the rest of the day I felt like someone cut off my arm...:-)
At this point I can still cut OK, it is the other stuff that is a priority.
Also, there has to be room for fencing in the garage!
On Wed, 20 Aug 2008 22:09:46 -0700, with neither quill nor qualm, "Michael Koblic" quickly quoth:
The shill bidder can hike up the auction amount by tens, hundreds, maybe even a thousand dollars. What're a few bucks in eBay fees to that? Shills also seldom win the bid.
Yeah, we'll all have to buy eBay Bucks or something...
-- It is pretty hard to tell what does bring happiness; poverty and wealth have both failed. -- Kin Hubbard
I get into jobs like that where machine tools don't help much. Currently I'm making a catalytic converter heat shield out of a damaged stainless steel chimney section. I haven't quite figured out how to make louvers on a curved surface yet. A new heat shield from the dealer is $120 and NOT stainless.
Sheet metal is easier to profile if you attach it to plywood. I put screws and washers around the edges and in waste areas and then fasten temporary wooden strips across the sheet close to the edges being cut to keep them from lifting, which is a problem with end mills.
My circular routing jig consists of a tapped block bolted to a laminate trimmer (small router) connected to a ball rod end (for go- kart steering) with threaded rod. The rod end pivots on a bolt, held squarely upright by a tee nut, in the center of the plywood. To feed it in or out I flip the rod end half a turn, which is more certain than two opposed nuts and accurate enough for most such jobs. You could make a similar rig without machining by bolting strips of slotted angle to opposites sides of the tool's base plate, with the holes for the threaded rod far enough out to clear the collet wrench. To start a cut I slide it onto the center bolt with the rod end raised upward and lower it level to feed outward. The rod end is a close fit on the bolt even at an angle.
My rotary table is too lightweight for serious circular milling, not that I haven't tried. Its 40:1 reduction ratio means all rotation is relatively low speed like a clock's minute hand. That's one reason for a motorized one. A hand-held tool becomes harder to control as the metal thickness increases and the rotary table keeps the cutter and work from jumping around and your hands further away. I think you could use it and the table feed to engrave the Roman numerals.
Maybe you could find or make a pottery wheel with a frame around it to support your tools. If you set it up right the rotating tool will drive the wheel. That's how I ground down the front motorcycle tire for my sawmill. I could control the speed by changing the angle that the grinding disk crossed the tire. The top speed my 7" angle grinder could drive it to was about 80 MPH which is reasonable as long as the wheel is balanced and the axle is bolted to 150 pounds of steel.
A motorcycle front wheel might work well for you since you can easily attach plywood to the brake rotor and your work to the plywood. They have enough inertia that momentarily grinding parallel to the circumference won't speed them up dangerously. The axle will catch your disk if it comes loose although spinning particle board weakened by screw holes is a hazard to whatever part of you is in line.
The chuck configuration is plywood or particle board with screws, soldered tabs, clamps, low-strength glue, XC ski wax, whatever you can loosen to remove the work. The traditional woodworking trick is to put a sheet of newspaper in the glue joint. The newspaper splits when you push a chisel into the joint.
Supposedly if you first turn the OD of the disk round you can hold it very securely in a shallow press-fit recess turned in the wood and have the entire face free. The heat from polishing tightens the grip. You can pop it out with a dowel through a small predrilled hole. The Holtzapffel book that came from says the press fit only lasts a day because the wood changes size with humidity overnight.
I flatten large surfaces with an angle grinder, sander and (rarely) buffing pad and check for flatness with a straight edge or the reflection of fluorescent light tubes. The tiny fraction of my work that could be called "art" has a matte finish to avoid the problem. I was looking over my neighbor's custom Harley the other day and noticed that none of the hand-buffed chromed surfaces were really flat, but I had to look hard to see that. It's good to have loud neighbors when you run a chop saw outdoors.
The trouble with using a drill press is that the head and table twist easily on the round column unless you add more fasteners. I chiseled out the flange at the top of the column so the head can move down and added an extra clamp screw. If necessary I could make a tailstock plug that fits the center hole in the baseplate and use the table collar to attach a toolrest. The quill's antirotation key was a setscrew that I replaced with a longer clamp screw with the end filed cylindrical to fit the quill slot and a nail for the tee handle. That was before I had any other machine tools.
A hand drill attached to a heavy plank would work if you could clamp it tight enough, maybe bed it in Bondo. You could use a steady rest instead of a tailstock and cut out to the very end of the gnomon. I've seen a suggestion (Lautard?) for a home-made wooden steady rest that simply had a screw bearing downward and another behind the work. Cutting pressure pushed the work back and up against the screws.
If I had to make a lathe by hand I'd mount four 1" pillow blocks on a heavy wooden beam, two for the headstock and two for the tail. The large drive pulley with a 1" bore came off an old clothes dryer. The first spindle would be keyed shafting and I'd grind and hand-turn a center point on the head and tail spindles. Then I'd use it to turn
3/4" pipe (1.050" OD) down to fit into the pillow blocks for a hollow threaded spindle and attach a wooden face plate with a floor flange.
The chuck would be a 1/2" Jacobs drill chuck on a long 1/2-20 bolt, centered by four setscrews at each end and driven by a cross pin. I have one on my little AA lathe where it fits the spindle thread and a larger Jacobs headstock chuck for the SB in an adapter made from a pipe coupling. They are very handy but not too rigid, so tailstock or steady rest support is necessary.
The riser blocks to increase the lathe's capacity only have to be identical, not any exact height, and the spindles can be aligned with a long shaft through all the bearings. Instead of a carriage on a precise bed it would have an X-Y table that clamps to the beam wherever it's needed, like lathes before Maudslay.
I've collected most of the parts except that the head and tailstocks came off scrapped lathes. It will be assembled only when needed for large-diameter wheels and pulleys.
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