Last weekend, I installed a brand new TT RL 53 on a Raptor.When installing the glow plug , i noted that it was not threading in easily.  I am extra careful while working with the engine, as its easy to spoil the threads on the alumnium engine head.

I tried a couple of times, but since it was not fitting properly, i took it out. and noted a very thin sliver of aluminium. I removed it, and the glow plug went in properly ! .

Now, i could have possible spoiled the threads on the engine, but i do not think i exterted enough pressure to cut through the threads. I somehow think this was left behind from production ?

I have read several articles where they advise that before the first start of the engine you should wash the insides out. I have never followed , but after this incident, i think that might be sensible to do in future ?

I have read reports of metal shavings inside brand new engines.  But it is not common for brands like OS or TT... cannot be completely ruled out either, it seems.

Gaurav,
From what you say, it is possible that some swarf may have remained embedded within the plug thread while the thread was being cut in the head bore.
If the plug seated properly afterwards and there was no leakage, that could be the only reason which comes to my mind