New challenge

[Jorgens]

Hi all!

I am about to turn some aluminium discs in the lathe, and they are too big in diameter (Ø 200) for my chuck. The discs are 30 mm wide.
How would you recommend I go at this job? I was thinking of letting a external company boring a hole in the center and make a press fit axle to go through that i can fit in the jaw, maybe Ø 30 mm, and weld it. After finishing one side, I can attach it directly in the jaws.
Any other suggestions?

Br
Jørgen, Norway.

[Harold_V]

I'm not fond of the idea of welding on aluminum so it can be machined. One of the problems is the immediate loss of the aged condition, rendering the material quite soft. It machines poorly in that condition.

Without knowing more, my idea may not be good, but if you can do so, consider holding the piece by the tailstock, running a live center under load. You'd use a round piece of stock, faced parallel, with a center hole in which the live center bears, so you don't alter the piece being machined. This piece should be reasonably thick, so it applies pressure across the entire surface when in use. The work piece would be pressed against either a face plate or one of your chucks, with the jaws removed.

If you take light cuts, you should be able to machine the piece adequately so it can then be chucked. That, of course, depends on if you can press the part while machining the diameters you hope to machine. If the part requires full facing, or a small diameter turn, that may not work. Note, too, that if you have a light duty machine, this operation may not be successful. It works fine on industrial rated machines, however.

Harold

[Jorgens]

I'm not fond of the idea of welding on aluminum so it can be machined. One of the problems is the immediate loss of the aged condition, rendering the material quite soft. It machines poorly in that condition.

Without knowing more, my idea may not be good, but if you can do so, consider holding the piece by the tailstock, running a live center under load. You'd use a round piece of stock, faced parallel, with a center hole in which the live center bears, so you don't alter the piece being machined. This piece should be reasonably thick, so it applies pressure across the entire surface when in use. The work piece would be pressed against either a face plate or one of your chucks, with the jaws removed.

If you take light cuts, you should be able to machine the piece adequately so it can then be chucked. That, of course, depends on if you can press the part while machining the diameters you hope to machine. If the part requires full facing, or a small diameter turn, that may not work. Note, too, that if you have a light duty machine, this operation may not be successful. It works fine on industrial rated machines, however.

Harold

Hi.

Thanks! I`ll see if this is a way of doing it. It`s a Colchester student from 1965. Only thing i am concerned about in your suggestion is the safety, if the piece somehow should come loose..

Jørgen

[Harold_V]

Thanks! I`ll see if this is a way of doing it. It`s a Colchester student from 1965. Only thing i am concerned about in your suggestion is the safety, if the piece somehow should come loose..

Jørgen

Precisely why I suggested that light cuts are in order. Also, make certain that your live center is up to the task. The part should be loaded quite well. Don't run excessively fast, so if it does move, it won't become a projectile. Check tailstock pressure regularly, as heating may create over-pressure rapidly. You want it tight, but not excessively.

Harold

[earlgo]

Pressing the work piece against the faceplate is a great idea and might be improved by the addition of a sticky back fine abrasive disk on the faceplate to improve friction. If one uses the same criteria used for grinding wheel flanges for the disk then it should be at least 1/3 the part diameter. Following the same guidelines, the pusher plate should be no less than 1/2" (13mm) if made from steel, to be assured of a flat contact. Half again as thick if one uses aluminum.

Remember if you choose to weld the aluminum that if 2024 alloy is used it is subject to heat cracking if proper procedures are not followed.

--earlgo

[redneckalbertan]

Would a double sided tape work as well in this application?

[Mr Ron]

Here is a fixture I made to turn wheel flanges. it requires a center hole and an offset hole to keep the disk from turning loose. The drive pin is on the backside of the wheel, so it won't show. Dimensions shown are in imperial (inches) measurements. You can tailor the dimensions to suit your own requirements.

[Russ Hanscom]

When welding is mentioned, warpage is the first thing that comes to mind. As mentioned, double sided tape or super glue might be the ticket.

[david5605]

Do you have a faceplate for your lathe? You could use toe clamps (cam lock clamps?) and hold it by its outside edge. That would allow you to turn about half the thickness. Then flop the disk around and readjust the clamps to hold it by the previously turned diameter. Then finish turning the diameter.

Here is one example of the kind of clamps I'm thinking about.
http://www.amazon.com/Mitee-Bite-Hex-He ... B002SIDUOA

I bought some 'no-name' brand ones that were a lot cheaper than my example above. Can't remember where I got mine. ENCO/MSC/SHARS/EBAY?

[ctwo]

I was able to face a penny by hot gluing it to a piece of faced stock. I made a double headed penny. Just heat to remove, but light cuts were required to avoid heating and release of the part during machining.

Tom Lipton (OxToolCo) discusses this and suggests another kind of glue that dissolves in acetone (or isopropyl?) He also suggests some kind of double stick tape.

I've also pinched a part against the open jaws, de-jawed chuck, face plate, or turned stock with a live center against a tube or other piece of stock. It works well, but you need to have your tail stock set right, both height and sxs.