Lathe purchase. Which one ?

[steve6690]

I'm toying with the idea of getting a lathe. It would be used for making dive light housings and battery canisters. I would be working with 2" to 3" aluminium round bar for the light heads, and probably 3" aluminium tube with 1/4" wall for the battery canister. The battery canisters would be no more than 500mm in length.
The design involves basic operations - think nothing more complicated than a Maglite. Needs to be metric. My current project is a light head approximately 60mm OD which needs to have an external thread for a cap to screw down on. Cable entry is via an M12 x 1.5 gland at the back. I'm considering a Sieg C4 :

http://www.axminster.co.uk/product-Axminster-SIEG-Axminster-SIEG-C4-Metal-Bench-Lathe-715020.htm

or Sieg C6B :

http://www.axminster.co.uk/product-Axminster-SIEG-Axminster-SIEG-C6B-Variable-Speed-Lathe-377299.htm

or maybe this Jet :

http://www.axminster.co.uk/product-Jet-BD-920-W-Metal-Turning-Lathe-365595.htm

I like my toys so I might want to have a go at a cnc conversion in the future.
Would any of these be suitable for what I have in mind ?. It's been about 25 years since I was shown how to use a lathe so I would be starting out from basics again. Thanks for any advice..

steve

 

[PhotonFanatic]

. . .

The battery canisters would be no more than 500mm in length.
. . .

steve

Uh, 500mm? If you expect to turn that length, in that diameter, you are going to need something a lot larger than any of those machines that you linked to. :devil:

 

[steve6690]

I'd be taking a 500mm length of ally tube and basically tidying up the outside, plus putting an internal thread for an end cap to screw in to. I could make do with 400mm...

 

[PhotonFanatic]

Steve,

And just how would you thread internally on a 3" diameter bar that sticks out about 15-16" from your chuck? And it would be protruding that much since those chucks on the machines you referenced, can not pass through stock of that diameter.

If you just look at the end of that tube, it will go flying--unless it is held by a steady rest.

There is a reason that guys like Mac, Brian and Will are buying big machines--they do want to work on Mags, but they also want to be able to work close to the headstock, i.e., with the piece inside the chuck and protruding the minimum amount needed for the operation.

 

[steve6690]

I assumed it would require support at the opposite end to the chuck, but I didn't know whether it was possible to support the work well enough to do the threading..
Am I going to find a machine that can pass that kind of diameter tube through without spending thousands ? 3" is an absolute maximum. I could go with 2 1/4" as a minimum..
None of the machines I linked to can do more than 38mm, 1 1/2". From the sound of it this is not going to be workable...

 

[precisionworks]

I could go with 2 1/4" as a minimum..

That size spindle bore gets you into a large machine ...

http://www.lionlathes.com/lathes/16m.html#

2 3/32" spindle bore

16" swing

6 hp motor

4000#

If that isn't quite big enough, click here: http://www.youtube.com/watch?v=SAHg7j_I8DA&feature=related

 

[steve6690]

Nice, but too rich for my blood. I can't really justify that kind of money for a first lathe. It's a shame I can't do what I need with a smaller machine. I may have to forget about making the canisters and just stick to the light heads. they are probably no more than 4 or 5 inches in length...

 

[will]

I have a mini lathe. I have worked on Mag heads by chucking on the inside and using a live center on the tailstock. I can use the same setup for a Mag body, up to a 3D size. note - I can only work on the outside of lights.

 

[gadget_lover]

Steve,


If you just look at the end of that tube, it will go flying--unless it is held by a steady rest.

There is a reason that guys like Mac, Brian and Will are buying big machines--they do want to work on Mags, but they also want to be able to work close to the headstock, i.e., with the piece inside the chuck and protruding the minimum amount needed for the operation.

PhotonFanatic obliquely referenced the technique that you will need to use. A steady rest is not terribly expensive, nor it it hard to use. It's job is to hold the end furthest from the chuck while you work on it.

Combine that with a chuck big enough to hold the inside of the tube, and you have it made.

Make sure that you get a lathe that has enough carriage travel to get to the end of that 15 inch tube. Buying a lathe with 20 inches between centers may mean that the longest piece you can thread is 14 - 18 inches. Really, no BS. Try to find a review of the machine that tells you what the carriage travel is. Ideally, do not buy a machine without looking at one first.

You can see an example of how a 7x10 lathe can't work on a 10 inch piece at http://www.candlepowerforums.com/vb/showpost.php?p=995442&postcount=103

Good luck on your quest.


Daniel

 

[wquiles]

There is a reason that guys like Mac, Brian and Will are buying big machines--they do want to work on Mags, but they also want to be able to work close to the headstock, i.e., with the piece inside the chuck and protruding the minimum amount needed for the operation.

+1. Spot on Fred. The larger lathe not only allows for working on larger/longer pieces (longer distance between centers), but since I can now get a 3D body almost completely inside the chuck/spindle, I can do it "safely". In addition, with my new PM12x36 I can now properly/safely use/support the heavy 6" Bison set-tru chuck: like many here stated, it was too big/heavy chuck for the 8x machine - it was not a safe/optimum setup. This increase safety was (along with wanting a more rigid machine), the single more important reason why decided to sell the almost-new 8x machine and I save money to buy a larger lathe

A piece of advice that is given here often is so true: buy the largest/heaviest lathe that you can afford for your budget and space available. I finally did that on my latest lathe purchase (PM12x36) and I am finally happy with my setup and feel safer as well

Will

 

[modamag]

I've had a C6B. It's a pretty well built lathe for <$1K. But lack the regidity that I want to hog out large chuck of metal.

If you do decide with a "smaller" lathe. Take a look at the Syil C6 conversion. It's < $4K converted.

500mm will present problem for you unless you're using steady rest. I would look into a larger lathe or contracting a local machine shop with the capability if this is a small quantity.

 

[cmacclel]

I don't even think the 12" x 36" Grizzly's steady rest would have held 3"?? For what you wanting to do you need at minimum a lathe with a 6" chuck and that brings you to the 12" x 36" size at around 1500lbs.


Mac

 

[steve6690]

Thanks everyone. It strikes me that another option might be to simply construct the battery canister prototypes on a piece of tube 6" or so in length. We are basically talking about a piece of tube with a thread at either end, into which a cap screws. The central body is unmodified tube so it's length would be irrelevant for prototyping purposes.. The important bits are at each end. I also may design end caps that are push-fit as opposed to screw-in. Either way, I can prototype in a short length of tube and use a local shop to then manufacture the tubes in the correct length. I wouldn't need such an expensive lathe then...