We made some Sapele corners out of a double layer of 8/4 stock early this week. We used a 3/8" 2 flute HSS upcut spiral bit to drill 5 indexing holes in both the layers. Dowels were then inserted in the holes to facilitate alignment of the two layers when being glued together. We may have drilled as many as 60 holes this way. It was a 5 ipm z-axis feed rate and bit withdrawal from the holes.....so quite slow. It was also a single full depth plunge vs. say 1/2" increments.
One of my guys just brought that ISO-30 tool holder nut into the office. It is covered in globs of black goo as are the collet etc. This is a black material so the initial thought is charred dust, but it is also soft and pasty in nature so that doesn't sound like charred dust. They are telling me there was no smoke what-so-ever coming out of the holes during drilling, or any other sign of anything wrong.
Note that we tried to use a 3/8" drill be first but there was too much flex in the bit and we were getting oversize holes. We don't do this sort of thing very often so didn't have proper drill tooling for the CNC. When the need for this has come up we've always ended up just drilling with an upcut spiral bit. While spindle bearing wear is a concern we don't do enough of this sort of thing to worry, and the slow feed rates hopefully compensate for extra stress.
Has anyone else ever seen this sort of material show up after a similar operation? It is a very strange occurrence.
Thanks,
BH Davis