Hello all.  I am new to the forum but have been building and customizing clubs for myself for years.  Up until now, all new sets I have assembled have been .370 parallel hosels and I have been able to prep/clean them out with a perfectly sized drill bit (turned it by hand, gently).  Recently, I came across a set of brand new Wilson Staff V4 iron heads and I jumped on them being a life long Wilson Staff fan.  The hosels are .355 tapered so my drill bit does not fit.  For one reason or another, there seems to be a lot of residue left over from manufacturing and I cannot seem to remove it. There is residue on both the walls and base of the hosel. First, I tried cleaning them out with the spiral brushes I use when cleaning out hosels after pulling shafts but this did not do the job. Next, I took a small flathead screwdriver to see if I could chip some of it away.  No luck.  The shafts will not fit into the hosels at this point so I am at a standstill.  Any ideas on how to prep these .355 tapered hosels so I can get going on my winter project?  Thank you in advance for your help.