A Thanks and a WTF?

Hi, wanted to say a quick thanks for the recommendations on my drill thread, bought the Makita and very happy with it too

Managed to drill out two screws in the wheel of my guzzi that had proved impossible thus far, and so I get to my WTF?

The screws in question (philips) hold three 'spoke cover' plates to the wheel itself. See attached photo of the remains of them once i'd extracted them - are these in fact self-tapping wood-screws? The thread looks much coarser than the usual machine screw and bolt threads elsewhere in the bike.

Any idea why this thread might be used? I suppose I'll have to try and source suitable replacements, or maybe it would be preferable to fill the holes with metal filler and re-tap for machine screws. The plates carry no load; they're just decorative. Reason for taking them apart is to get the wheels powdercoated.

Oddly the screw itself hadn't got stuck in the threaded hole, it was the underside of the screw-head which had corroded/welded itself to the surface under it. DSCF1861.jpgDSCF1862.jpg

Look like self tappers. Just replace with new ones with a blob of coppaslip.

Aluminium is quite soft so there's all kinds of self tappers that fairly fly into it, saving time at the manufacturing end, if not at the "trying to find exact replacements when working on later" end.

Thanks fellas - never seen it before so it took me completely by surprise

Back wheel out now, 3 more screws to remove. Have covered in plus-gas and hoping they come out as intended rather than via another drilling out marathon