Some StarWars Model Parts

wildo said:
2) Why is a small lathe better suited for making parts like this? Is it because of the mass of the carriage? Do the smaller lathes have higher spindle speeds and finer control? It's unclear to me why a smaller lathe would make it easier to create this part over a hobby sized lathe like the SB9a. What am I missing??
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I can only speak to the Sherline lathe but as to why it is better for this kind of work vs a typical larger lathe:
  • It is small, so you can get close to your work. Most Sherline owners work sitting down, often with an Optivisor on their head. You're comfortable, stable and you can see.
  • Unlike most larger lathes, a Sherline lathe has 20tpi leadscrews and accurate laser-cut index markings on the zero-set hand wheels. This allows for very accurate movement in X and Y; I can interpolate and dial in a 0.00025" depth of cut by eye and the lathe will cut it assuming you have the right tool. Contrast that to most lathes with a 10 tpi leadscrew; they are a knife, the Sherline is a scalpel.
  • The tool post on a Sherline lathe mounts directly to the cross slide; a compound is not used for most operations. Once locked in, the tool is essentially a part of the structure of the lathe. Although small in size, a Sherline lathe is extremely rigid. With a good tool, a Sherline lathe will easily take a 0.050" depth of cut in mild steel and 0.100" on aluminum; yeah, I mean 0.100" off the diameter in steel and 0.200" of the diameter in aluminum. Not too bad for a small lathe.
  • Sherline cross slides have T-slots running the length of the cross slide table. This allows you to mount a parting tool at the rear of the part. This is used for parting but also for precision grooving. On your part, I would have used a parting tool to accurately demarcate the two larger sections by cutting down to the dimension of the smaller diameter; then I just have to turn the small diameters down and I'm done. A rear mounted parting tool on a Sherline lathe can part most materials at very high speeds - brass and aluminum at 2800 rpm, mild steel at half that speed - and it will have zero issues with chatter or digging in. Try that on your 9" SB.
  • My lathe has a variable speed DC motor connected to the main leadscrew to give me complete control of the cut. By independently varying the speed of the spindle and feed screw, I can dial in a cut on the fly in real time. Imagine the finish you would get if you took a finish cut on aluminum at 2800 rpm with a very slow power feed while using a sharp HSS tool optimized to cut aluminum. Cannot get that with carbide on a lathe tied to its gearing.
  • The Sherline is a change gear, manual drive lathe. Most think this is a disadvantage but when working with small, precision class threads it is actually an advantage. When was the last time you cut a Class 3, 4-48 thread 1/4" long in tool steel? I did that three weeks ago and hit my thread tolerances the first time. This involves turning the diameter of the screw to within a few tenths, then cutting the threads accurately. Try that on a 1340 and let us know how it goes.
I suspect most guys who look down on the Sherline lathe have never even seen one, much less used one to turn real parts. If they had, they would have a different opinion of this lathe. It definitely has its limitations, mainly the size of the work that can be done on it, but within its work envelope it is a real tool meant for precision work like you needed for this job, Wildo.

As @Choiliefan said, add some good HSS tools that are capable of taking fine cuts without deflecting much at all and you have a very good system to use when you need it.
 
Mike- **thank you!!**

This is exactly what I was hoping someone would chime in with. I've seen regularly that people say "Oh- that's easier on a small lathe" and I've never understood why. They both have cross slides; they both have lead screws; they both have rigidity. But actually, some of the points you made I was not aware of. I can't even take a 0.050" cut on the SB... hahaha!

It seems maybe I need to look into a Sherline lathe! I actually really love making super small parts; I just really hate working with a worn out lathe while doing it. Big thanks for the explanation; that's exactly the learning I was looking for.
 
What actually makes the Sherline lathe work well for me are the cutting tools I use. The typical Sherline lathe using a standard geometry turning tool can maybe take a 0.020" DOC max. The geometry I use enables the lathe to work much better and more accurately. It may be that learning to grind a good tool will greatly improve the function of your lathe, too.
 
Actually, when you think about it, what would you use to make tiny parts for a watch?
Most of the points Mikey made apply to the Taig lathe as well
Wildo: why can't you take a 50 thou cut on your SB? It should do it I would think
 
I suspect the tool is another key reason for the reduced performance of your lathe, Will. Carbide on a small lathe just doesn't work as well. Maybe time to jump into HSS tool grinding?
 
mikey said:
I suspect the tool is another key reason for the reduced performance of your lathe, Will. Carbide on a small lathe just doesn't work as well. Maybe time to jump into HSS tool grinding?
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No question about it. And it's an area I really want to improve on. I'm hoping to win a pedestal grinder in an auction here in the next few days.

I also got a picture of the parts installed on the model. He's making a stage scale model of the escape pod from the beginning of Star Wars Episode 4. Apparently that means that this model is the exact same size as the one they used to film the scene.
296829
 
Very cool! Your parts came out nice, Will, honest. I wish you were close to me. I would love to show you how easy it would be to make those parts on a Sherline lathe.

If you don't win the pedestal grinder, maybe consider a good belt sander as an option. I find it to be a better machine, for me anyway. If I can help you, please let me know.
 
Nice job!!! I do a lot of micro machining…A LOT! And after reading this thread, I just had to chime in. Sorry to some folks, but there is absolutely no need for a small lathe to make those parts…not at all. I have several Levin lathes, that’s beside the point. My 14” lathe could have done the job without hindrance. And I understand the need for Carbide tool bits. But for the Hobby Shop (not a production environment) using Carbide for everything, IMHO can be a waste of money. I use HSS for almost everything and carbide when HSS does not hold up…Dave
 
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