Shouldn't need to be using them in his own time. He was taken on with the understanding that he didn't know how to weld. There should be a training system in place. Its like throwing a non swimmer in the deep end and expecting them to compete in the olympics, without the training, it won't happen.If your boss can be persuaded to let you 'play' with the machine on your own time for free
I know of at least 3 companies, all who I've worked for in the past, that employ "time-served", "self-taught" welders, with no formal qualifications, nor are there any specific weld tests performed, merely, lay a bead on this and we'll see how good you are. The most recent one, I walked from after they had a college kid welding on lifting eyes to containers that at the end of the process, we're going to be in excess of 8t! When one literally peeled away from the structure, I downed tools. It wasn't the first time it had happened, and it certainly wasn't the first complaint that had been made in a week, more like 10 or 11 consecutive complaints in the space of 2 days that the welds were cold, and down hand certainly wasn't the way to be performing a critical weld like this!Double or even treble that for critical welds as if/when any go tits up both you and your employer could be facing serious charges and/or civil claims for damages/injuries.
Ideally the company should pay or help to pay for one of the recognised welding certificates, day release or evening college training etc, without those your choice of future work will be very limited,
Nonsense apart, is this job going to lead to you getting recognised qualifications and portable skills applicable to a range of employers or self employment? If it isn't, carry on, try to introduce the idea but be on the lookout for something which will do that.