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Sieg C0

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Sieg C0

Unread postAuthor: Alster370 » Tue Oct 25, 2011 8:26 am

I have as my first lathe, a seig C0. Although I don't have a great amount of knowledgeable on the intricate workings of lathes such as these, I can definitely find faults, which usually only need a little altering to be fixed.
My Problems so far:

1.)If the work piece is threaded, the chuck will not hold it accurately

2.)On smooth pieces made of stronger materials(steel) The item will untighten itself eventually from the chuck due to the friction.

If anyone could give me advice on how to fix these problems I would greatly appreciate it, or other tips on how to improve my lathes performance or accuracy.

I have already tuned the electronics for better torque at lower speeds and am planning a home-made milling attachment that I can clamp into the tool post. Most of my inspiration comes from here :http://varmintal.net/alath.htm, Its just a case of adapting it for my lathe instead.
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Re: Sieg C0

Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 8:31 am

Alster370 wrote:1.)If the work piece is threaded, the chuck will not hold it accurately


No self centering chuck will hold a threaded section in a lathe accurately...

2.)On smooth pieces made of stronger materials(steel) The item will untighten itself eventually from the chuck due to the friction.


This could be an indicator that you're trying to take away too much material at a time, making deeper cuts than the lathe can take. Try shallower cuts.
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Unread postAuthor: Alster370 » Tue Oct 25, 2011 8:41 am

No self centering chuck will hold a threaded section in a lathe accurately...


Really? I never knew that. Its probably because the threads are consistent all the way round the work-piece, and thus I thought it wouldn't be a problem. :oops: Its fine with things like shrader valves, but brass fittings are a disaster in comparison.

This could be an indicator that you're trying to take away too much material at a time, making deeper cuts than the lathe can take. Try shallower cuts.


Its only with steel really, you have to go really slow, its not as bad now with the modified electronics but I tend to stick with aluminium or brass anyway. No real need to use steel.

Il see If I can get a better quality chuck, its just hard to find one that fits my lathe.

Also would the quality of the fit in the lathe chuck also be down to how round the work-piece actually is? Im guessing so.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 25, 2011 10:14 am

Alster370 wrote:Really? I never knew that. Its probably because the threads are consistent all the way round the work-piece, and thus I thought it wouldn't be a problem. :oops: Its fine with things like shrader valves, but brass fittings are a disaster in comparison.


Threads are rarely perfectly concentric with the part, besides they offer minimal contact area and are easily crushed by the chuck.

Its only with steel really, you have to go really slow, its not as bad now with the modified electronics but I tend to stick with aluminium or brass anyway. No real need to use steel
.

Again, if you're fine with softer materials then the issue is probably that you're trying to remove too much material at once. Remeber you can't make the same depth of cut in steel than what works with brass and aluminium.

Il see If I can get a better quality chuck, its just hard to find one that fits my lathe.


A bad chuck obviously doesn't help but I doubt this is the issue.

Also would the quality of the fit in the lathe chuck also be down to how round the work-piece actually is? Im guessing so.


It is a reflection of it but ideally you should plan your cuts in such a way that you have to do as few chuck changes as possible. If you look at the "dimply" pengun cutting plan you'll see that LeMaudit was careful with this.
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Unread postAuthor: DYI » Tue Oct 25, 2011 11:45 am

Brass fittings are a disaster in comparison because there's typically hardly any length to hold them on - the threads are tapered pipe threads and thus can't be held by the chuck, and the body doesn't tend to have long flat sections.

A self-centring chuck can grip threaded sections just fine - I hold pieces of 3/4" and 1" threaded rod in my self-centring 3-jaw chuck regularly with no inaccuracies in the finished parts that I can measure (down to 0.001", at least). Brass would cause problems due, as JSR mentioned, to the softness of the material and subsequent crushing of the threads. It should work just fine with any steel over 600MPa tensile strength, possibly even less.
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Unread postAuthor: USGF » Tue Oct 25, 2011 3:14 pm

Alster370 wrote:
: Its fine with things like shrader valves, but brass fittings are a disaster in comparison.



If you have a straight coupling, we often chuck up the coupler, thread in the part you want to modify, do your deed and then remove it from the coupling. No damaged threads, good concentricity if the chuck and coupling run true. You want to find barstock turned couplings, not the cheap cast ones. Those will not run concentric.

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Unread postAuthor: Alster370 » Wed Oct 26, 2011 11:21 am

In the end its probably not capable of what I thought. I visioned it being able to cut 2" steel pistons for steam engines and the like. :shock:. Il see if axe minster will take it back for a reasonable price, then il save up for a proxxon lathe or something.
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 26, 2011 12:22 pm

You probably could, just veeeeeeerrryyyy slllooooooowwwwwllllyyyyyyyyyyyyyyyyyy
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Unread postAuthor: Alster370 » Wed Oct 26, 2011 1:23 pm

maybe I could just hire you as my machinist :D. Just got to get good with some sort of 3dcad first. :roll:
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 26, 2011 1:39 pm

The Sherline is a miniature lathe and will also cut veeeeeeerrryyyy slllooooooowwwwwllllyyyyyyyyyyyyyyyyyy, which means the part will veeeeeeerrryyyy expeeeensssiiivveeee ;)
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Unread postAuthor: jor2daje » Wed Oct 26, 2011 2:54 pm

you should just be patient and get to know your machine, Ive seen some incredible impressive stuff made on those lathes. Dont expect perfection, look at every project as a learning experience.
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