If, like me, you tend to buy chunks of aluminium from ebay (other sources are available) then 6082 T6 is the most common stuff on offer. It turns nicely but I have not needed to weld it – but I'm sure there is advice on this on the web. Or even here in a moment or two.

Cheers, Tim

This can be a bit of a can of worms because not all Aluminium's are weldable. Typically you would not weld the 2000, 7000 and a most of the 5000 series. The 6000 series alloys are the only ones with any strength that are normally considered for welding. 6082 welds quite happily. Just remember that the tensile strength in the HAZ of the weld joint will only be around 50 MPa (295 MPa in T6 condition) and will need heat treating if you need the full strength?

Others may say you can weld other grades quite happily. But as a professional engineer, I would advise caution if there are any significant factors that may result in high loads and fatigue.

Dave

It will also depend on the grade of alloy used for the pulley in the first place – so the properties of this are unknown, but might be an appropriately econonical type for casting, without necessarily a great concern about welding qualities.

however, I would suggest that a pulley in normal use is not a highly stressed item, and it may not matter if the tensile strength is somewhat (even substantially) down.

I would be concerned if the item was in heavy use in an industrial environment, in which case the recommended replacement should be purchased from the original manufacturer. For the amateur workshop in light use, one not be too worried – if a welded inserted piece seems to be fully and evenly bonded, that is good enough.

Martin

Off the shelf stuff stands a good chance of being a 6000 series, in this case round thats 6082 and probably T6 tempering. Will be hard to find any other grade often special order and twice the price.

6082 is good enough for MOD work untreated after welding.
6082 not the best to turn either though work with it daily.

In short think it there wont be that great deal of difference for a small piece to bodge and insert to getting a blank to make a pulley.

Some pulleys are cast though never knowingly came across any made from 6082, therefore good chance if you do make an insert it wont weld.

Your gummy alloy may not have been an alloy at all – pure aluminium meets this description.

Regards, Tim